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Relaxin acts as a pregnancy-specific signal in feline species, but specific information about protein structure and binding is essential for the improvement of pregnancy diagnosis in endangered feline species, like the Iberian lynx. To generate a felid-specific relaxin antibody, the DNA and protein sequences of lynx and cat were determined and peptides were chosen for antibody generation. In addition, relaxin and relaxin receptor (RXFP1) mRNA expressions were measured in uteri and ovaries of pregnant domestic cats and lynx placentae. Using real-time PCR and immunohistochemistry, it was established that feline placenta is the main source of relaxin during pregnancy. In other tested tissues, relaxin mRNA expression was weak. The RXFP1 mRNA expression was found mainly in cat uterine tissue and feline placentae. It was assumed that these tissues were main targets for relaxin. In the ovary, relaxin immunostaining was associated with blood vessels, signifying its role in vascularization.

The response of cats to dietary sodium selenite (Na(2) SeO(3)) and organically bound selenium was studied in two separate studies with four cats per treatment and three levels of selenium supplementation (targets 1.0, 1.5 and 2.0 μg/g DM) for each Se source. Whole blood and plasma selenium concentrations and glutathione peroxidase (GPx) activity were determined at 7-time points across the 32-day study. Faeces were quantitatively collected during the last 8 days and urine was collected daily during both studies. The basal diet used had a low apparent faecal selenium absorption of 25.3 ± 3.0%. Daily faecal and urinary selenium excretion increased linearly with increasing selenium intake for both Se sources. Urinary selenium concentration of the cats fed the supplemented diets increased rapidly (∼2 days) and remained constant throughout the remainder of the study. Apparent faecal selenium absorption was high for both selenium sources (73.2% and 80.0%). Plasma, and to a lesser extent, whole blood selenium concentrations increased in a dose-dependent manner with supplementation. Whole blood and plasma GPx activity were highly variable and showed a variable response to dietary selenium intake. Cats closely regulate selenium homeostasis through increasing urinary excretion whilst faecal absorption remains unaffected., (© 2011 Blackwell Verlag GmbH.)

The objectives of this study were to determine differences in apparent total tract energy and macronutrient digestibility, fecal and urine characteristics, and serum chemistry of domestic cats fed raw and cooked meat-based diets and extruded diet. Nine adult female domestic shorthair cats were utilized in a replicated 3 × 3 Latin square design. Dietary treatments included a high-protein extruded diet (EX; 57% CP), a raw beef-based diet (RB; 53% CP), and a cooked beef-based diet (CB; 52% CP). Cats were housed individually in metabolic cages and fed to maintain BW. The study consisted of three 21-d periods. Each period included diet adaptation during d 0 to 16; fecal and urine sample collections during d 17 to 20; and blood sample collection at d 21. Food intake was measured daily. Total feces and urine were collected for determination of nutrient digestibility. In addition, a fresh urine sample was collected from each cat for urinalysis, and a fresh fecal sample was collected from each cat for determination of DM percentage and ammonia, short-chain fatty acid (SCFA), and branched-chain fatty acid (BCFA) concentrations. All feces were scored after collection using a scale ranging from 1 (hard, dry pellets) to 5 (watery, liquid that can be poured). Blood was analyzed for serum metabolites. Apparent total tract DM, OM, CP, fat, and GE digestibilities were greater (P ≤ 0.05) in cats fed RB and CB than those fed EX. Total fecal SCFA concentrations did not differ among dietary treatments; however, molar ratios of SCFA were modified by diet, with cats fed RB and CB having an increased (P ≤ 0.05) proportion of fecal propionate and decreased (P ≤ 0.05) proportion of fecal butyrate compared with cats fed EX. Fecal concentrations of ammonia, isobutyrate, valerate, isovalerate, and total BCFA were greater (P ≤ 0.05) in cats fed EX compared with cats fed RB and CB. Our results indicated that cooking a raw meat diet does not alter apparent total tract energy and macronutrient digestibility and may also minimize risk of microbial contamination. Given the increasing popularity of feeding raw diets and the metabolic differences noted in this experiment, further research focused on the adequacy and safety of raw beef-based diets in domestic cats is justified.

Ghrelin, a 28-amino acid-long peptide with an n-octanoyl modification at Ser(3), has been isolated from rat and human stomachs as an endogenous ligand for the growth hormone secretagogue receptor. It is very important to study the ghrelin from mammals (especially, domestic animals) that serve as human companions, food resources, and model organisms. We purified feline and caprine ghrelin and observed that the administration of synthetic ghrelin increased plasma growth hormone (GH) levels in cats and goats. Therefore, we believe that ghrelin may play important roles in GH release in mammals., (Copyright © 2012 Elsevier Inc. All rights reserved.)

During mammalian preimplantation development, two successive differentiation events lead to the establishment of three committed lineages with separate fates: the trophectoderm, the primitive endoderm and the pluripotent epiblast. In the mouse embryo, the molecular mechanisms underlying these two cell fate decisions have been studied extensively, leading to the identification of lineage-specific transcription factors. Species-specific differences in expression patterns of key regulatory genes have been reported, raising questions regarding their role in different species. The aim of the present study was to characterise the gene expression patterns of pluripotency (OCT4, SOX2, NANOG) and differentiation (CDX2, GATA6)-related markers during feline early development using reverse transcription-quantitative polymerase chain reaction. In addition, we assessed the impact of in vitro development on gene expression by comparing transcript levels of the genes investigated between in vitro and in vivo blastocysts. To normalise quantitative data within different preimplantation embryo stages, we first validated a set of stable reference genes. Transcript levels of all genes investigated were present and changed over the course of preimplantation development; a highly significant embryo-stage effect on gene expression was observed. Transcript levels of OCT4 were significantly reduced in in vitro blastocysts compared with their in vivo counterparts. None of the other genes investigated showed altered expression under in vitro conditions. The different gene expression patterns of OCT4, SOX2, CDX2 and GATA6 in cat embryos resembled those described in mouse embryos, indicative of a preserved role for these genes during early segregation. However, because of the absence of any upregulation of NANOG transcription levels after embryonic genome activation, it is unlikely that NANOG is a key regular of lineage segregation. Such results support the hypothesis that the behaviour of early lineage markers can be species specific. The present study also revealed a pool of maternal NANOG mRNA transcripts, the role of which remains to be elucidated. Comparing transcription levels of these genes between in vivo and in vitro blastocysts revealed low levels of OCT4 mRNA in the latter, which may contribute to the reduced developmental competence of embryos under suboptimal conditions.

Objective: To determine the effects of increases in dietary intake of polyunsaturated and saturated fatty acids on plasma lipid and lipoprotein concentrations and activity of associated enzymes in healthy domestic cats., Animals: 16 healthy adult sexually intact female cats., Procedures: A baseline diet (40% energy from fat) and 4 test diets, with increased amounts of fat (51% and 66% energy from fat) from the addition of polyunsaturated and saturated fatty acids, were fed for 6 weeks each. Plasma cholesterol, triglyceride, and lipoprotein cholesterol concentrations, along with activities of lipoprotein lipase, hepatic lipase, and lecithin-cholesterol acyl transferase, were measured at the end of each feeding period., Results: Diet, amount of fat, or ratio of polyunsaturated to saturated fatty acids had no effect on plasma concentrations of cholesterol, triglycerides, and very-low-density or high-density lipoproteins or the activity of lecithin-cholesterol acyl transferase. Low-density lipoprotein concentrations were significantly lower in cats fed a high-fat diet containing polyunsaturated fatty acids. Lipoprotein concentration and hepatic lipase activity were significantly higher in cats fed the fat-supplemented diets, and this was unrelated to whether diets were enriched with polyunsaturated or saturated fatty acids., Conclusions and Clinical Relevance: Diets containing up to 66% of energy from fat were tolerated well by healthy cats and did not affect plasma lipid concentrations. Therefore, high-fat diets probably will not contribute to hypercholesterolemia or hypertriglyceridemia in cats.

Objective: To develop a formula for correcting slope-intercept plasma iohexol clearance in cats and to compare clearance of total iohexol (TIox), endo-iohexol (EnIox), and exo-iohexol (ExIox)., Animals: 20 client-owned, healthy adult and geriatric cats., Procedures: Plasma clearance of TIox was determined via multisample and slope-intercept methods. A multisample method was used to determine clearance for EnIox and ExIox. A second-order polynomial correction factor was derived by performing regression analysis of the multisample data with the slope-intercept data and forcing the regression line though the origin. Clearance corrected by use of the derived formula was compared with clearance corrected by use of Brochner-Mortensen human and Heiene canine formulae. Statistical testing was applied, and Bland-Altman plots were created to assess the degree of agreement between TIox, EnIox, and ExIox clearance., Results: Mean ± SD iohexol clearance estimated via multisample and corrected slope-intercept methods was 2.16 ± 0.35 mL/min/kg and 2.14 ± 0.34 mL/min/kg, respectively. The derived feline correction formula was Cl(corrected) = (1.036 × Cl(uncorrected)) - (0.062 × Cl(uncorrected)(2)), in which Cl represents clearance. Results obtained by use of the 2 methods were in excellent agreement. Clearance corrected by use of the Heiene formula had a linear relationship with clearance corrected by use of the feline formula; however, the relationship of the feline formula with the Brochner-Mortensen formula was nonlinear. Agreement between TIox, EnIox, and ExIox clearance was excellent., Conclusions and Clinical Relevance: The derived feline correction formula applied to slope-intercept plasma iohexol clearance accurately predicted multisample clearance in cats. Use of this technique offers an important advantage by reducing stress to cats associated with repeated blood sample collection and decreasing the costs of analysis.

Production of cloned mammals by somatic cell nuclear transfer is associated with functional and structural abnormalities of placentation and with abnormal fetal development. A proteomic analysis was performed in domestic cats (Felis catus) to compare cloned term placentas (CTP) obtained from cesarean section (CS) to control placentas obtained from CS or vaginal delivery. The expression of 20 proteins was altered in CTP (p<0.05) compared to control placentas. The two control groups showed that the method of delivery, vaginal delivery or CS, did not affect protein expression (p>0.05). A total of 13 proteins were up-regulated in CTP, including apoptosis-related cathepsin D (CD), annexin A1 and heat shock protein 27 (HSP 27), and seven proteins were down-regulated in CTP, including prohibitin (PHB). The expression of PHB and CD was confirmed by Western blotting and immunofluorescence staining. The abnormal expression of PHB and CD correlated with the generation of reactive oxygen species, leading to decreased mitochondrial membrane potential and telomeric DNA, which are associated with cellular senescence and apoptosis. In summary, a specific pattern of abnormal protein expression is associated with the impaired development and functions of cloned placentas and hence with decreased fetal viability. Strategies aimed at restoring normal placental protein expression may increase the efficiency of somatic cell nuclear transfer and transgenic cat production and help restore endangered species., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The purpose of the present study was first to identify drivers of variance in plasma metabolite profiles of cats and dogs that may affect the interpretation of nutritional metabolomic studies. A total of fourteen cats and fourteen dogs housed in environmentally enriched accommodation were fed a single batch of diet to maintain body weight. Fasting blood samples were taken on days 14, 16 and 18 of the study. Gas chromatography-mass spectrometry (GC-MS), liquid chromatography (LC)-MS/MS and solid-phase extraction-LC-MS/MS analyses were used for metabolite profiling. Principal component (PC) analysis that indicated 31 and 27 % of the variance was explained in PC1 and PC2 for cats and dogs, respectively, with most individuals occupying a unique space. As the individual was a major driver of variance in the plasma metabolome, the second objective was to identify metabolites associated with the individual variation observed. The proportion of intra- and inter-individual variance was calculated for 109 cat and 101 dog metabolites with a low intra-individual variance (SD < 0.05). Of these, fifteen cat and six dog metabolites had inter-individual variance accounting for at least 90 % of the total variance. There were four metabolites common to both species (campesterol, DHA, a cholestenol and a sphingosine moiety). Many of the metabolites with >75 % inter-individual variance were common to both species and to similar areas of metabolism. In summary, the individual is an important driver of variance in the fasted plasma metabolome, and specific metabolites and areas of metabolism may be differentially regulated by individuals in two companion animal species.

The physiological relevance of oestradiol (E2) on post-orchiectomy (OX) food intake control was evaluated in six adult, male, domestic, short-hair cats. Jugular venous plasma E2 and oestrone (E1) concentrations were determined weekly before OX and immediately after OX in a cross-over trial of two 3-week periods in which E2 (0.5 μg) or vehicle (0.1 ml/kg) was subcutaneously injected daily and blood was sampled 4 h later. Plasma E1 and E2 concentrations before OX were 32 (SE 8.3) and 4.3 (SE 1.0) pg/ml, respectively. Following OX, plasma concentrations of E2 were decreased (P = 0.04) while those of E1 were unchanged. Injections of E2 increased (P = 0.02) plasma E2 towards pre-OX concentrations. In a second cross-over trial, plasma E1 and E2 were determined weekly during the last 3 weeks of two 8-week periods in which food was continuously presented or restricted to 110 % of pre-OX amounts. Continuous food presentation compared with restricted food presentation resulted in greater body weight (6.4 (SE 0.4) v. 5.4 (SE 0.4) kg, P = 0.02) and body fat percentage (29 (SE 3) v. 23 (SE 2) %, P = 0.09) but no significant changes were observed in plasma E1 and E2 concentrations. Hence, circulating E2 appears to be reduced by OX, while it is not significantly changed by body-fat gain. The amount of E2 injected after OX was not supraphysiological; it restored plasma E2 to pre-OX concentrations and reduced food intake in five of the six cats by a mean of 14 (SE 3) %.

A charge made against feeding dry foods to cats is that the high carbohydrate (i.e. starch) content results in high blood glucose levels which over time may have detrimental health effects. The present study determined the post-meal concentrations of plasma glucose and insulin in adult cats (seven males and four females) and dogs (Labrador retrievers; four males and five females) fed dry diets with low-starch (LS), moderate-starch (MS) or high-starch (HS) levels. In a cross-over design with at least 7 d between the test meals, plasma glucose and insulin concentrations were measured following a single meal of a LS, MS and HS diet (209 kJ/kg bodyweight). Only the HS diet resulted in significant post-meal increases in plasma glucose concentration in cats and dogs although the time-course profiles were different between the species. In cats, plasma glucose concentration was significantly increased above the pre-meal concentration from 11 h until 19 h after the meal, while in dogs, a significant increase above baseline was seen only at the 7 h time point. Plasma insulin was significantly elevated in dogs 4-8 h following the MS diet and 2-8 h after the HS diet. In cats, plasma insulin was significantly greater than baseline from 3-7 and 11-17 h after the HS diet. The time lag (approximately 11 h) between eating the HS diet and the subsequent prolonged elevation of plasma glucose concentration seen in cats may reflect metabolic adaptations that result in a slower digestive and absorptive capacity for complex carbohydrate.

Little nutritional information has been collected from domestic cats fed raw meat diets. The objective of the present study was to evaluate differences in N metabolism of domestic cats fed raw beef-based diet (66 % crude protein (CP) and 20 % fat), bison-based diet (49 % CP and 39 % fat), elk-based diet (79 % CP and 6 % fat) and horse-based diet (60 % CP and 26 % fat). A total of eight intact adult female cats were fed to maintain body weight in a cross-over design. Daily food intake, faecal and urinary outputs, and N metabolism were measured. Dietary N was highly digestible (96.8 (SEM 0.7)) for all treatments. Urinary N accounted for a majority of total N excretion, and differences in total N excretion reflect differences in urinary N. Differences in N intake and N absorption were due to differences in CP levels among diets. N retention was similar to values reported in the literature for domestic cats fed purified and traditional extruded diets. Despite differences in protein concentrations and N intake, all raw meats tested maintained N metabolism.

Data from intravenous (i.v.) glucose tolerance tests suggest that glucose clearance from the blood is slower in cats than in dogs. Since different physiological pathways are activated following oral administration compared with i.v. administration, we investigated the profiles of plasma glucose and insulin in cats and dogs following ingestion of a test meal with or without glucose. Adult male and female cats and dogs were fed either a high-protein (HP) test meal (15 g/kg body weight; ten cats and eleven dogs) or a HP + glucose test meal (13 g/kg body-weight HP diet + 2 g/kg body-weight D-glucose; seven cats and thirteen dogs) following a 24 h fast. Marked differences in plasma glucose and insulin profiles were observed in cats and dogs following ingestion of the glucose-loaded meal. In cats, mean plasma glucose concentration reached a peak at 120 min (10.2, 95 % CI 9.7, 10.8 mmol/l) and returned to baseline by 240 min, but no statistically significant change in plasma insulin concentration was observed. In dogs, mean plasma glucose concentration reached a peak at 60 min (6.3, 95 % CI 5.9, 6.7 mmol/l) and returned to baseline by 90 min, while plasma insulin concentration was significantly higher than pre-meal values from 30 to 120 min following the glucose-loaded meal. These results indicate that cats are not as efficient as dogs at rapidly decreasing high blood glucose levels and are consistent with a known metabolic adaptation of cats, namely a lack of glucokinase, which is important for both insulin secretion and glucose uptake from the blood.

Compared with the normospermic domestic cat, sperm metabolic function is compromised in the teratospermic cat and cheetah, but the pathway(s) involved in this deficiency are unknown. Glycolysis is essential for sperm motility, yet it appears to function normally in spermatozoa of either species regardless of structural morphology. We conducted a comparative study to further understand the mechanisms of energy production in felid spermatozoa, with the hypothesis that oxidative phosphorylation is required for normal sperm function and is impaired in teratospermic ejaculates. Electroejaculates from both species were stained with MitoTracker to quantify mitochondrial membrane potential (MMP) or were incubated to assess changes in sperm function (motility, acrosomal integrity, and lactate production) after mitochondrial inhibition with myxothiazol. Sperm midpiece dimensions also were quantified. Sperm mitochondrial fluorescence (directly proportional to MMP) was ~95% lower in the cheetah compared with the normospermic and teratospermic cat, despite the cheetah having a 10% longer midpiece. In both species, MMP was increased 5-fold in spermatozoa with retained cytoplasm compared with structurally normal cells. Inhibition of oxidative phosphorylation impaired sperm function in both species, but a 100-fold higher inhibitor concentration was required in the cat compared with the cheetah. Collectively, findings revealed that oxidative phosphorylation was required for sperm function in the domestic cat and cheetah. This pathway of energy production appeared markedly less active in the cheetah, indicating a species-specific vulnerability to mitochondrial dysfunction. The unexpected, cross-species linkage between retained cytoplasmic droplets and elevated MMP may reflect increased concentrations of metabolic enzymes or substrates in these structures.

Objective: To determine whether therapeutic concentrations of levetiracetam can be achieved in cats and to establish reasonable i.v. and oral dosing intervals that would not be associated with adverse effects in cats., Animals: 10 healthy purpose-bred cats., Procedures: In a randomized crossover study, levetiracetam (20 mg/kg) was administered orally and i.v. to each cat. Blood samples were collected 0, 10, 20, and 40 minutes and 1, 1.5, 2, 3, 4, 6, 9, 12, and 24 hours after administration. Plasma levetiracetam concentrations were determined via high-performance liquid chromatography., Results: Mean ± SD peak concentration was 25.54 ± 7.97 μg/mL. The mean y-intercept for i.v. administration was 37.52 ± 6.79 μg/mL. Half-life (harmonic mean ± pseudo-SD) was 2.95 ± 0.95 hours and 2.86 ± 0.65 hours for oral and i.v. administration, respectively. Mean volume of distribution at steady state was 0.52 ± 0.09 L/kg, and mean clearance was 2.0 ± 0.60 mL/kg/min. Mean oral bioavailability was 102 ± 39%. Plasma drug concentrations were maintained in the therapeutic range reported for humans (5 to 45 μg/mL) for at least 9 hours after administration in 7 of 10 cats. Only mild, transient hypersalivation was evident in some cats after oral administration., Conclusions and Clinical Relevance: Levetiracetam (20 mg/kg) administered orally or i.v. to cats every 8 hours should achieve and maintain concentrations within the therapeutic range for humans. Levetiracetam administration has favorable pharmacokinetics for clinical use, was apparently tolerated well, and may be a reasonable alternative antiepileptic drug in cats.

Mirtazapine pharmacokinetics was studied in 10 healthy cats. Blood was collected before, and at intervals up to 72 h after, oral dose of 3.75 mg (high dose: HD) or 1.88 mg (low dose: LD) of mirtazapine. Liquid chromatography coupled to tandem mass spectrometry was used to measure mirtazapine, 8-hydroxymirtazapine and glucuronide metabolite concentrations. Noncompartmental pharmacokinetic modeling was performed. Median half-life was 15.9 h (HD) and 9.2 h (LD). Using Mann-Whitney analysis, a statistically significant difference between the elimination half-life, clearance, area under the curve (AUC) per dose, and AUC(∞) /dose of the groups was found. Mirtazapine does not appear to display linear pharmacokinetics in cats. There was no significant difference in glucuronidated metabolite concentration between groups. Pharmacodynamics was studied in 14 healthy cats administered placebo, LD and HD mirtazapine orally once in a crossover, blinded trial. In comparison with placebo, cats ingested significantly more food when mirtazapine was administered. No difference in food ingestion was seen between HD and LD, but significantly more behavior changes were seen with the HD. Limited serum sampling during the pharmacodynamic study revealed drug exposure comparable with the pharmacokinetic study, but no correlation between exposure and food consumed. Mirtazapine (LD) was administered daily for 6 days with no drug accumulation detected., (© 2010 Blackwell Publishing Ltd.)

Adiponectin is a key adipokine that regulates carbohydrate and lipid metabolism. It circulates in stable low (LMW) and high molecular weight (HMW) forms. The aims of this study were to characterize baseline adiponectin profiles (total, LMW and HMW multimers) in healthy cats and to assess the effects of varying dietary carbohydrate content on adiponectin profiles. Cats were maintained on a diet with moderate carbohydrate content (37% metabolisable energy [ME]) for 4 weeks and then randomly allocated to either a low carbohydrate (19% ME) or high carbohydrate (52% ME) diet for 4 weeks. Fasting and postprandial plasma adiponectin profiles were measured by ELISA and sucrose gradient/Western blot. After consuming the moderate carbohydrate diet for 4 weeks, fasting total, HMW and LMW plasma adiponectin concentrations were 5.0±0.6, 2.5±0.5 and 2.6±0.2 μg/mL, respectively. After changing to the low carbohydrate diet, fasting total adiponectin was unchanged but HMW adiponectin increased and LMW adiponectin decreased. No significant postprandial changes were observed. Cats consuming the high carbohydrate diet had increased fasting total and LMW adiponectin with no change in HMW adiponectin. In the postprandial state total adiponectin was reduced and there was a trend towards a decrease in HMW (p=0.086) but not LMW multimers. These data indicate that feline adiponectin multimer profiles are similar to those reported in other species and demonstrate that changes in plasma adiponectin occur in response to chronic and acute carbohydrate intake and these reflect differential changes in adiponectin multimers., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Glycoproteins (GPs) are known to be involved in the phenomenon of sperm maturation and capacitation. In the present study, we investigated the attachment of GPs on sperm cell membrane during the process of feline sperm maturation from testicular sperm to ejaculated sperm by using 8 FITC-labeled lectins. The results showed that 3 types of GPs were presented on testicular sperm and 7 on caput epididymal sperm. Corpus and cauda epididymal sperm and ejaculated sperm had GPs detected by 8 FITC-labeled lectins used in the present study. This study demonstrates the part of the characteristic of GPs that are present on the feline sperm cell membrane during the process of sperm maturation.

Short-chain fructooligosaccharides (scFOS) and galactooligosaccharides (GOS) are nondigestible oligosaccharides that result in a prebiotic effect in some animal species; however, the cat has not been well studied in this regard. This experiment evaluated scFOS and GOS supplementation on nutrient digestibility, fermentative end product production, and fecal microbial ecology of cats. Eight healthy adult cats were fed diets containing no prebiotic, 0.5% scFOS, 0.5% GOS, or 0.5% scFOS + 0.5% GOS (scFOS + GOS) in a replicated 4 × 4 Latin square design. Apparent total tract CP digestibility was decreased (P < 0.05) when cats were fed a diet containing scFOS + GOS compared with the other treatments. Dry matter, OM, acid hydrolyzed fat, and GE digestibilities were not different (P > 0.05) among treatments. Cats fed scFOS-, GOS-, and scFOS + GOS-supplemented diets had greater (P < 0.05) fecal Bifidobacterium spp. populations compared with cats fed the control diet. Fecal pH was less (P < 0.05) for cats fed the scFOS + GOS-supplemented diet compared with the control. Butyrate (P = 0.05) and valerate (P < 0.05) concentrations were greater when cats consumed the scFOS + GOS diet. Acetate tended (P = 0.10) to be greater when cats were fed the scFOS + GOS diet. Total short-chain fatty acid (P = 0.06) and total branched-chain fatty acid (P = 0.06) concentrations also tended to be greater when cats consumed the scFOS + GOS treatment. Fecal protein catabolites, including ammonia, 4-methylphenol, indole, and biogenic amines, blood lymphocytes, neutrophils, total white blood cell counts, or fecal DM concentration and output did not differ (P > 0.05) among treatments. Low level supplementation of scFOS, GOS, and their combination exert positive effects on select indices of gut health in cats.

The purpose of this study was to evaluate transepidermal water loss (TEWL), skin hydration and skin pH in normal cats. Twenty shorthaired European cats of both sexes were examined in the study. Measurements were taken from five different sites: the lumbar region, the axillary fossa, the inguinal region, the ventral abdominal region and the left thoracic region. In each of the regions, TEWL, skin hydration and skin pH were measured. The highest TEWL value was observed in the axillary fossa (18.22g/h/m(2)) and the lowest in the lumbar region (10.53g/h/m(2)). The highest skin hydration was found in the inguinal region (18.29CU) and the lowest in the lumbar region (4.62CU). The highest skin pH was observed in the inguinal region (6.64) and the lowest in the lumbar region (6.39). Statistically significant differences in TEWL were observed between the lumbar region and the left side of the thorax region (P=0.016), the axillary fossa (P=0.0004), the ventral region (P=0.005), and the inguinal region (P=0.009). There were significant differences in skin hydration between the lumbar region and the left thorax (P=0.000003), the axillary fossa (P=0.002), the ventral abdomen (P=0.03), and the inguinal region (P=0.0003) as well as between the thorax and the ventral abdomen (P=0.005). TEWL was higher in females (15g/h/m(2)) than in males (4.57g/h/m(2)). Skin hydration was higher in females (13.89CU) than in males (12.28CU). Significant differences were not found between males and females for TEWL and skin hydration. Skin pH was higher in males (6.94) than in females (6.54), which was significant (P=0.004)., (Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.)

Ronidazole (RDZ) is an effective treatment for feline Tritrichomonas foetus infection, but has produced neurotoxicity in some cats. An understanding of the disposition of RDZ in cats is needed in order to make precise dosing recommendations. Single-dose pharmacokinetics of intravenous (IV) RDZ and immediate-release RDZ capsules were evaluated. A single dose of IV RDZ (mean 9.2mg/kg) and a 95mg immediate-release RDZ capsule (mean 28.2mg/kg) were administered to six healthy cats in a randomized crossover design. Plasma samples were collected for 48 h and assayed for RDZ using high pressure liquid chromatography (HPLC). Systemic absorption of oral RDZ was rapid and complete, with detection in the plasma of all cats by 10 min after dosing and a bioavailability of 99.64 (±16.54)%. The clearance of RDZ following IV administration was 0.82 (±0.07) ml/kg/min. The terminal half-life was 9.80 (±0.35) and 10.50 (±0.82) h after IV and oral administration, respectively, with drug detectable in all cats 48h after both administrations. The high oral bioavailability of RDZ and slow elimination may predispose cats to neurotoxicity with twice-daily administration. Less frequent administration should be considered for further study of effective treatment of T foetus-infected cats., (Copyright © 2011 ISFM and AAFP. Published by Elsevier Ltd. All rights reserved.)

We examined the immunohistochemical distributions of natriuretic peptide receptor (NPR)-A, -B and -C that bind with natriuretic peptide hormones A, B and C in four healthy crossbreed young canine and feline cardiac tissues using specific antibodies against human antigens. Cross-immunoreactivities between antigens and antibodies were confirmed using western blot analysis. NPR-A and -C were expressed more strongly in dogs than cats. In both species, these expressions were stronger in the atria than the ventricles, with stronger expression in the left ventricles than the right. NPR-B was largely very weekly or undetected. In canine and feline cardiac tissues, the expressional distribution of NPR-A, -B, and -C closely matched with that of atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide as the ligands for corresponding receptors.

The domestic cat (Felis catus), a carnivore, naturally eats a very low carbohydrate diet. In contrast, the dog (Canis familiaris), a carno-omnivore, has a varied diet. This study was performed to determine the expression of the intestinal brush border membrane sodium/glucose cotransporter, SGLT1, sweet receptor, T1R2/T1R3, and disaccharidases in these species adapted to contrasting diets. The expression (this includes function) of SGLT1, sucrase, maltase and lactase were determined using purified brush border membrane vesicles and by quantitative immunohistochemistry of fixed tissues. The pattern of expression of subunits of the sweet receptor T1R2 and T1R3 was assessed using fluorescent immunohistochemistry. In proximal, middle, and distal small intestine, SGLT1 function in dogs was 1.9- to 2.3-fold higher than in cats (P = 0.037, P = 0.0011, P = 0.027, respectively), and SGLT1 protein abundance followed an identical pattern. Both cats and dogs express T1R3 in a subset of intestinal epithelial cells, and dogs, but not cats, express T1R2. In proximal and middle regions, there were 3.1- and 1.6-fold higher lactase (P = 0.006 and P = 0.019), 4.4- and 2.9-fold higher sucrase (both P < 0.0001), and 4.6- and 3.1-fold higher maltase activity (P = 0.0026 and P = 0.0005), respectively, in the intestine of dogs compared with cats. Dogs have a potential higher capacity to digest and absorb carbohydrates than cats. Cats may suffer from carbohydrate malabsorption following ingestion of high-carbohydrate meals. However, dogs have a digestive ability to cope with diets containing significant levels of carbohydrate.

The pharmacokinetic properties of marbofoxacin, a third generation fluoroquinolone, were investigated in 12 healthy adult cats after single subcutaneous (SC) administration of 2 mg/kg BW (Part I, n=8 cats) and 4 mg/kg BW (Part II, n=4 cats). In each part of the study blood and urine samples were collected before treatment and thereafter for 5 days. The plasma and urine concentrations of marbofloxacin were determined by HPLC with UV detection. Pharmacokinetic calculations were performed for each treated animal using an open one-compartment-model with first-order elimination after SC dosing. Marbofloxacin in plasma (means): Maximum concentrations (Cmax) of about 1.2 and 3.0 microg/ml were measured 2.3 and 4 hours (tmax) after dosing of 2 and 4 mg/kg BW, respectively. Elimination from the body was low with a total clearance (Cl/F) of approximately 0.1 l/h/kg for both dosages. The half-life (t 1/2) for this process was calculated with 8-10 hours. AUC increased almost proportional when doubling the dose, i.e., 19.77 +/- 6.25 microg * h/ml (2 mg/kg BW) and 51.26 +/- 11.83 microg * h/ml (4 mg/kg BW). Plasma kinetics measured were in accordance with data from literature. Marbofloxacin in urine (means): Maximum drug concentrations were detected 4 and 8 hours after dosing with 70 microg/ml (2 mg/kg BW) and 160 microg/ml (4 mg/kg BW), respectively. Inhibitory effects of the urinary matrix on the antimicrobial activity of the drug were taken into account when performing PK/PD calculations. However, a concentration-dependent bactericidal activity (Cmax/MIC > 8-10) which is claimed for fluoroquinolones was sufficiently met with focus on Escherichia (E.) coli (MIC90 0.5 microg/ml). In the same matrix a threshold value of 1.0 microg/ml was undercut 82 and 116 hours after SC dosing, respectively. Hence, a time-dependent bacteria killing kinetic (T > MIC) which may be of relevance for some Gram-positive germs like Staphylococcus spp. (MIC90 1.0 microg/ml) should be covered, too.

This study aimed to investigate the biotransformation of cat liver microsomes in comparison to dogs and humans using a high throughput method with fluorescent substrates and classical inhibitors specific for certain isozymes of the human cytochrome P450 (CYP) enzyme family. The metabolic activities associated with CYP1A, CYP2B, CYP2C, CYP2D, CYP2E and CYP3A were measured. Cat liver microsomes metabolized all substrates selected for the assessment of cytochrome P450 activity. The activities associated with CYP3A and CYP2B were higher than the activities of the other measured CYPs. Substrate selectivity could be demonstrated by inhibition studies with α-naphthoflavone (CYP1A), tranylcypromine/quercetine (CYP2C), quinidine (CYP2D), diethyldithiocarbamic acid (CYP2E) and ketoconazole (CYP3A) respectively. Other prototypical inhibitors used for characterization of human CYP activities such as furafylline (CYP1A), tranylcypromine (CYP2B) and sulfaphenazole (CYP2C) did not show significant effects in cat and dog liver microsomes. Moreover, IC50-values of cat CYPs differed from dog and human CYPs underlining the interspecies differences. Gender differences were observed in the oxidation of 7-ethoxy-4-trifluoromethylcoumarin (CYP2B) and 3-[2-(N, N-diethyl-N-methylamino)ethyl]-7-methoxy-4-methylcoumarin (CYP2D), which were significantly higher in male cats than in females. Conversely, oxidation of the substrates dibenzylfluorescein (CYP2C) and 7-methoxy-4-trifluoromethylcoumarin (CYP2E) showed significant higher activities in females than in male cats. Overall CYP-activities in cat liver microsomes were lower than in those from dogs or humans, except for CYP2B. The presented difference between feline and canine CYP-activities are useful to establish dose corrections for feline patients of intensively metabolized drugs licensed for dogs or humans., (© 2010 Blackwell Publishing Ltd.)

Cytochrome P450 2D (CYP2D) is one of the major metabolizing enzymes for drugs in humans and other mammals. Although domestic cats (Felis catus) are the most common companion animal in many countries, the properties of their drug-metabolizing system are largely unknown. We determined the complete cDNA sequence of the CYP2D open reading frame (1,500 bp) with both 5'- and 3'-untranslated regions in domestic cats. Feline CYP2D consists of 500 deduced amino acids and shows high homology with CYP2Ds of primates and rodents, particularly with the canine CYP2D homologue, and was designated as CYP2D6 based on its genomic structure. CYP2D6 transcripts were expressed predominantly in the liver and to a much lesser in the testis, suggesting the role of xenobiotic metabolism in the liver.

Cheetahs and certain other felids consistently ejaculate high proportions (≥ 60%) of malformed spermatozoa, a condition known as teratospermia, which is prevalent in humans. Even seemingly normal spermatozoa from domestic cat teratospermic ejaculates have reduced fertilizing capacity. To understand the role of sperm metabolism in this phenomenon, we conducted a comparative study in the normospermic domestic cat versus the teratospermic cat and cheetah with the general hypothesis that sperm metabolic function is impaired in males producing predominantly pleiomorphic spermatozoa. Washed ejaculates were incubated in chemically defined medium containing glucose and pyruvate. Uptake of glucose and pyruvate and production of lactate were assessed using enzyme-linked fluorescence assays. Spermatozoa from domestic cats and cheetahs exhibited similar metabolic profiles, with minimal glucose metabolism and approximately equimolar rates of pyruvate uptake and lactate production. Compared to normospermic counterparts, pyruvate and lactate metabolism were reduced in teratospermic cat and cheetah ejaculates, even when controlling for sperm motility. Rates of pyruvate and lactate (but not glucose) metabolism were correlated positively with sperm motility, acrosomal integrity, and normal morphology. Collectively, our findings reveal that pyruvate uptake and lactate production are reliable, quantitative indicators of sperm quality in these two felid species and that metabolic function is impaired in teratospermic ejaculates. Furthermore, patterns of substrate utilization are conserved between these species, including the unexpected lack of exogenous glucose metabolism. Because glycolysis is required to support sperm motility and capacitation in certain other mammals (including dogs), the activity of this pathway in felid spermatozoa is a target for future investigation.

The objective of this study was to investigate the metabolic pathways and routes of excretion of oral meloxicam in the cat. [(14)C]-meloxicam was administered orally to three fasted male cats. Urine, faeces, vomit and cage washes were collected over the following 144 h period. Blood was collected predosing and at 3 and 12 h postdosing. Metabolites were identified by HPLC/MS/MS. When possible a metabolic structure was proposed for each metabolite detected. Only unchanged meloxicam was identified in plasma. Five major metabolites were detected in urine and four in faeces, which were identified by HPLC/MS/MS as products of oxidative metabolism. No conjugated metabolites were detected. Elimination occurred early (61% during the first 48 h). A total of 21% of the recovered dose was eliminated in urine (2% as unchanged meloxicam, 19% as metabolites) and 79% in the faeces (49% as unchanged meloxicam, 30% as metabolites). The results indicate that after oral administration the major route of excretion of meloxicam in the cat is faecal and that the main pathway of biotransformation of meloxicam in the cat is oxidation.

The purpose of this study was to determine the iodine (I) requirement in adult cats. Forty-two healthy euthyroid cats (1.6-13.6 years old) were utilized in a randomized complete block design. Cats were fed a dry basal diet (0.23 mg/kg I) for a minimum of 1 month (pre-test) then switched to a different basal diet supplemented with seven levels of KI for 1 year (experimental period). Analysed I concentrations were 0.17, 0.23, 0.47, 1.1, 3.1, 6.9 and 8.8 mg I/kg diet [dry matter (DM) basis] and used to construct a response curve. Response variables included I concentrations in serum, urine and faeces, urinary I:creatinine ratio, I balance, technetium(99m) pertechnetate (Tc(99m)) thyroid:salivary ratio, complete blood count and serum chemistries as well as serum thyroid hormone profiles. No significant changes in food intake, weight gain or clinical signs were noted. Serum I, daily urinary I, daily faecal I and urinary I:creatinine ratio were linear functions of iodine intake. An estimate of the I requirement (i.e. breakpoint) was determined from regression of Tc(99m) thyroid:salivary ratio (scintigraphy) on I intake at 12 months [0.46 mg I/kg diet (DM basis) as well as 9 months I balance (0.44 mg I/kg diet (DM)]. The I requirement estimate determined in our study at 12 months for adult cats (0.46 mg I/kg) was higher than current Association of American Feed Control Officials (AAFCO) recommendations (e.g. 0.35 mg I/kg), but was lower than the 2006 National Research Council (NRC) I recommended allowance (e.g. 1.4 mg I/kg).

Sex steroids, i.e. progesterone (P(4)) and 17beta-estradiol (E(2)), fluctuate during the feline estrous cycle and their alterations correspond to many events in cat reproduction. In order to investigate possible effects of sex steroids on prostaglandin (PG) secretion in the cultured endometrial cells, mRNA expressions coding for PG-endoperoxide synthase (PTGS2) in the epithelial and stromal cells harvested with sex steroids were studied by RT-PCR. The effects of ovarian steroids on PG secretion in the epithelial and stromal cells were also investigated. E(2) at a dose 10(-7)M significantly increased prostaglandin F2alpha (PGF(2alpha)) secretion in the epithelial cells (P<0.01). PGF(2alpha) production was intensified by the treatment in combination with both steroids (P<0.001). P(4) at any dose alone had no effect on PGF(2alpha) secretion in the epithelial cells, whereas at a dose 10(-5)M enhanced prostaglandin E2 (PGE(2)) production (P<0.05). The ovarian steroids stimulated both PGF(2alpha) and PGE(2) in the epithelial cells of the feline endometrium via an E(2) receptor (ESR1)- and P(4) receptor (PGR)-dependent genomic-pathway. In contrast to the epithelial cells, neither P(4) nor E(2) affected PG secretion in the stromal cells. PTGS2 mRNA expression was not affected by ovarian steroids in either cell types. The overall results suggest that PG secretion is regulated by P(4) and E(2) and this effect is not due to changes in PTGS2 mRNA expression., (Copyright 2010 Elsevier B.V. All rights reserved.)

The present study assessed the effect of separate reduction of each energy-delivering nutrient - protein, fat and carbohydrate - on glucose tolerance and insulin response in a strict carnivore: the domestic cat (Felis catus). Three isoenergetic, home-made diets with the following energetic distribution, low protein (LP): protein 28 % of metabolisable energy; fat 43 %; nitrogen-free extract 29 %; low fat: 47, 27 and 25 %; low carbohydrate (LC): 45, 48 and 7 %, were tested in a 3 x 3 Latin square design. Nine healthy normal-weight cats were randomly assigned to each of the diets in a random order at intervals of 3 weeks. At the end of each testing period, intravenous glucose tolerance tests were performed. Plasma glucose concentrations and area under the glucose curve showed no differences. Area under the insulin curve was lower when cats were fed the LP diet, and the second insulin peak tended to be delayed when the LC diet was fed. In contrast to other studies, in which energy sources were elevated instead of being reduced, the present trial contradicts the often suggested negative impact of carbohydrates on insulin sensitivity in carnivores, and shows that reducing the dietary carbohydrate content below common amounts for commercial foods evokes an insulin-resistant state, which can be explained by the cats' strict carnivorous nature. It even points to a negative effect of protein on insulin sensitivity, a finding that corresponds with the highly gluconeogenic nature of amino acids in strict carnivores.

In veterinary medicine, the characterization of a drug's pharmacokinetic (PK) properties is generally based upon data that are derived from studies that employ small groups of young healthy animals, often of a single breed. These are also the data from which population predictions are often generated to forecast drug exposure characteristics in the target population under clinical conditions of use. In veterinary medicine, it is rare to find information on the covariates that can influence drug exposure characteristics. Therefore, it is important to recognize some of the factors that can alter the outcome of PK studies and therefore potentially alter the pharmacological response. Some of these factors are easily identified, such as breed, gender, age, and body weight. Others are less obvious, such as disease, heritable traits, and environmental factors. This manuscript provides an overview of the various stressors (such as disease, inflammation, pregnancy, and lactation) that can substantially alter drug PK. Part II of this series provides an overview of the potential impact of physiological variables such as age, weight, and heritable traits, on drug PK. Ultimately, failure to identify appropriate covariates can lead to substantial error when predicting the dose-exposure relationship within a population.

Administration of iodinated contrast medium interferes with iodide uptake in the human thyroid gland and compromises diagnostic thyroid scintigraphy and radioiodine treatment for 4-6 weeks. However, the degree and duration of inhibition of thyroid uptake of pertechnetate (99mTcO4-) by iodinated contrast medium has not been established in any species. The main objective of this study was to better understand the temporal characteristics and magnitude of inhibition of feline thyroid uptake of 99mTcO4- due to iohexol administration. Routine thyroid scintigraphy was performed in eight cats by intravenous (IV) injection of 185 MBq (5 mCi) of 99mTcO4- both 4 days before and 0, 1, 3, 7, 14, and 28 days after IV administration of 880 mg I/kg iohexol (240 mg I/ml). Thyroid scintigraphy data were used to calculate thyroid:salivary gland ratios (T:S) and the percentage of total injected 99mTcO4- dose uptake within the thyroid (%TU) at 20 min postinjection. After iohexol administration, mean T:S was significantly decreased below baseline only on day 1. At no point during the study did any cat have a T:S that fell below the published normal reference range of 0.71 +/- 0.14. There was a significant decrease in %TU on day 1, 3, and 14; however, at no point during the study, did any cat have a %TU that fell below the published normal reference ranges of 0.64 +/- 0.57, 0.68 +/- 0.9, or 0.75 +/- 1.38.

Human acute intermittent porphyria (AIP), the most common acute hepatic porphyria, is an autosomal dominant inborn error of heme biosynthesis due to the half-normal activity of hydroxymethylbilane synthase (HMB-synthase). Here, we describe the first naturally occurring animal model of AIP in four unrelated cat lines who presented phenotypically as congenital erythropoietic porphyria (CEP). Affected cats had erythrodontia, brownish urine, fluorescent bones, and markedly elevated urinary uroporphyrin (URO) and coproporphyrin (COPRO) consistent with CEP. However, their uroporphyrinogen-III-synthase (URO-synthase) activities (deficient in CEP) were normal. Notably, affected cats had half-normal HMB-synthase activities and elevated urinary 5-aminolevulinic acid (ALA) and porphobilinogen (PBG), the deficient enzyme and accumulated metabolites in human AIP. Sequencing the feline HMB-synthase gene revealed different mutations in each line: a duplication (c.189dupT), an in-frame 3 bp deletion (c.842&#95;844delGAG) identical to that causing human AIP and two missense mutations, c.250G>A (p.A84T) and c.445C>T (p.R149W). Prokaryotic expression of mutations c.842&#95;844delGAG and c.445C>T resulted in mutant enzymes with <1% wild-type activity, whereas c.250G>A expressed a stable enzyme with approximately 35% of wild-type activity. The discolored teeth from the affected cats contained markedly elevated URO I and III, accounting for the CEP-like phenocopy. In three lines, the phenotype was an autosomal dominant trait, while affected cats with the c.250G>A (p.A84T) mutation were homozygous, a unique recessive form of AIP. These animal models may permit further investigation of the pathogenesis of the acute, life-threatening neurological attacks in human AIP and the evaluation of therapeutic strategies. GenBank Accession Numbers: GQ850461-GQ850464.

Information regarding the reproductive biology of black-footed cats (BFC) and sand cats (SC) is extremely limited. Our objectives were to: (1) validate fecal hormone analysis (estrogens, E; progestagens, P; androgens, T) for noninvasive monitoring of gonadal activity; (2) characterize estrous cyclicity, ovulatory mechanisms, gestation, and seasonality; and (3) evaluate male reproductive activity via fecal androgen metabolites and ejaculate traits. In both species, the estrous cycle averaged 11-12 days. In BFC (n=8), estrus lasted 2.2+/-0.2 days with peak concentrations of E (2962.8+/-166.3 ng/g feces) increasing 2.7-fold above basal concentrations. In SC (n=6), peak concentrations of E (1669.9+/-83.5 ng/g feces) during estrus (2.9+/-0.2 days) were 4.0-fold higher than basal concentrations. Nonpregnant luteal phases occurred in 26.5% (26 of 98) of BFC estrous cycles, but were not observed in SC (0 of 109 cycles). In both species, P concentrations during pregnancy were elevated (32.3+/-3.0 microg/g feces BFC; 8.5+/-0.7 microg/g feces SC) approximately 10-fold above basal concentrations. Fecal T concentrations in males averaged 3.1+/-0.1 microg/g feces in BFC and 2.3+/-0.0 microg/g feces in SC. Following electroejaculation, 200 to 250 microl of semen was collected containing 29.9 (BFC) to 36.5 (SC)x10(6) spermatozoa with 40.4 (SC) to 46.8 (BFC)% normal morphology. All females exhibited estrous cycles during the study and spermatozoa were recovered from all males on every collection attempt, suggesting poor reproductive success in these species may not be due to physiological infertility.

Glimepiride and nateglinide are two common oral hypoglycemic agents currently being used with humans suffering from Type 2 diabetes mellitus. Neither drug has been tested with cats thus far and it is currently unknown whether either of these drugs exert any effect in cats or not. The objective of this study was to determine the effect of glimepiride and nateglinide on glucose and insulin responses in healthy control cats, in order to determine their potential use in diabetic cats. The intravenous glucose tolerance tests was carried out since it is an excellent test for evaluating pancreatic beta-cell function for insulin secretion. Alterations in the insulin secretion pattern can be perceived as the earliest sign of beta-cell dysfunction in many species, including cats. Nateglinide demonstrated a quick action/short duration type effect with serum glucose nadiring and insulin response peaking at 60 and 20 minutes, respectively. Alternatively, glimepiride is medium-to-long acting with serum glucose nadiring and insulin response peaking at 180 minutes and 60 minutes, respectively. Nateglinide's potency was evident allowing it to induce a 1.5-2 higher preliminary insulin peak (3.7 +/- 1.1 pg/ml) than glimepiride's (2.5 +/- 0.1 pg/ml), albeit only for a short period of time. Because glimepiride and nateglinide have a shared mode of action, no significant differences in overall glucose AUC(0-360 min) (24,435 +/- 2,940 versus 24,782 +/- 2,354 mg min/dl) and insulin AUC(0-360 min) (410 +/- 192 versus 460 +/- 159) in healthy control cats were observed. These findings may provide useful information when choosing a hypoglycemic drug suited for the treatment of diabetic cats depending on the degree of diabetes mellitus the cat is suffering from.

The dose-related antinociceptive effects of intravenous (IV) buprenorphine were evaluated in cats. Thermal (TT) and mechanical threshold (MT) devices were used for nociceptive stimulation. After baseline threshold recordings, buprenorphine was administered IV (0.01, 0.02 or 0.04 mg/kg; B1, B2 and B4, respectively) in a randomised, blinded and cross-over study. Data were analysed by ANOVA (P<0.05) using 95% confidence intervals (CI). TT increased 15, 30, 45 min and 1 (5.2+/-2.7 degrees C), 2, 3 and 4 h after B1; 15, 30, 45 min and 1 (5.1+/-3.9 degrees C) and 2 h after B2, and 15, 30, 45 min and 1 (5.4+/-3.3 degrees C), 2, 3, 6 and 8 h after B4. MT increased 15 and 45 min after B2 (260+/-171 mmHg), and 30 (209+/-116 mmHg) and 45 min and 1 and 2 h after B4. At 45 min, MT values were significantly higher after B2 compared to B1 (P<0.05). With MT, B2 and B4 produced more antinociception and longer duration of action than B1, respectively. No dose response to thermal stimulation was detected.

Permeability glycoprotein (P-gp) is a membrane-bound efflux pump that exports various substances out of the cell. Variations in P-gp expression play an important role in susceptibility to toxic substances, drug efficacy and disease risk. In the present study, the distribution of the MDR1-gene product P-gp was determined in normal tissues of domestic shorthair cats using immunohistochemistry. Two monoclonal antibodies C494 and C219 were used, recognizing a different epitope on the human P-gp molecule. A consistent positive immunolabelling was obtained. The tissue distribution and cellular locations with antibody C494 were similar to those in man and dogs; with liver, colon, adrenal cortex and brain capillaries being consistently and intensely labelled. However, the immunolabelling in the kidney was in contradiction to man and dogs. The C219 antibody seems to react with a specific form of P-gp, only expressed in feline tissues with a barrier function, i.e. endothelia of the brain, testes and ovaries, and intestinal epithelial cells in contact with the lumen.

Objective: To determine whether a glomerular filtration rate (GFR) assay based on serum iohexol clearance can be used to predict carboplatin clearance in cats., Animals: 10 cats with tumors., Procedures: GFR was measured concurrently by use of plasma clearance of technetium Tc 99m-labeled diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) to yield GFR(99mTc-DTPA) and serum clearance of iohexol to yield GFR(Iohexol). A single dose of carboplatin was administered IV as a bolus. Dose was calculated by use of a target value for the area under the plasma platinum concentration-versus-time curve (AUC(Target)) and estimation of platinum clearance (CL(PT)) derived from GFR(99mTc-DTPA) as follows: dose = AUC(Target) x 2.6 x GFR(99mTc-DTPA) x body weight, where AUC(Target) is 2.75 min.mg.mL(-1). Plasma platinum concentrations were measured via atomic absorption spectrophotometry. Values for GFR(99mTc-DTPA) and GFR(Iohexol) were compared by use of least-squares regression and Bland-Altman analysis. Least-squares regression was used to determine whether CL(PT) could be predicted from GFR(99mTc-DTPA) or GFR(Iohexol) (or both)., Results: GFR(99mTc-DTPA) and GFR(Iohexol) were strongly correlated (r = 0.90), but GFR(Iohexol) values were significantly larger by a factor of approximately 1.4. Platinum clearance had a significant linear relationship to GFR(99mTc-DTPA) (CL(PT) = 2.5 x GFR(99mTc-DTPA)) and to GFR(Iohexol) (CL(PT) = [1.3 x GFR(Iohexol)] + 1.4)., Conclusions and Clinical Relevance: In cats, serum iohexol clearance was an accurate predictor of CL(PT) and can be used to calculate the carboplatin dose as follows: dose = AUC(Target) x ([1.3 x GFR(Iohexol)] + 1.4) x body weight.

Ketohexokinase (KHK) metabolizes dietary fructose and is an important regulator of hepatic glucose metabolism. The veterinary literature contains conflicting data regarding the role of KHK in feline fructose metabolism. The study objectives were to determine tissue expression of KHK mRNA and protein in cats, with special emphasis on hepatic expression. KHK mRNA and protein expression were determined using routine RT-PCR and immunoblot techniques. KHK mRNA was detected in feline liver, pancreas, spleen and striated muscle but not in lung. The partial sequence of feline KHK mRNA obtained was highly similar to known KHK mRNA sequences. Immunoblot studies confirmed KHK protein expression in the feline liver. The tissue distribution of KHK mRNA in cats is similar to KHK expression in other species. KHK mRNA and protein expression in feline liver is consistent with previous reports of hepatic fructokinase activity in this species.

Objective: To investigate the effect of therapeutic dosages of meloxicam on the plasma clearance of iohexol in healthy, euvolemic, conscious cats fed a sodium-replete diet., Animals: 6 healthy adult neutered male cats., Procedures: For each treatment period in a masked, randomized, crossover study, cats were administered either no treatment or meloxicam. Iohexol clearance studies were performed before the treatment period began (baseline) and on the final day of the treatment period. Iohexol concentrations were determined by use of a high-performance liquid chromatography assay, and plasma iohexol clearance as a marker of glomerular filtration rate was calculated by use of a 1-compartment model., Results: No significant treatment effect was detected. Mean +/- SE iohexol clearance for cats administered meloxicam (3.31 +/- 0.27 mL/min/kg) was not significantly different from mean baseline value for the meloxicam treatment period (3.07 +/- 0.32 mL/min/kg)., Conclusions and Clinical Relevance: In this study, short-term meloxicam administration did not measurably alter the glomerular filtration rate as assessed via plasma clearance of iohexol. This suggests that renal prostaglandins in cats did not have a measurable effect on glomerular filtration rates in healthy, euvolemic, conscious states as determined on the basis of methods used in this study.

Objective: To evaluate the effects of increasing doses of remifentanil hydrochloride administered via constant rate infusion (CRI) on the minimum alveolar concentration (MAC) of isoflurane in cats., Animals: 6 healthy adult cats., Procedures: For each cat, 2 experiments were performed (2-week interval). On each study day, anesthesia was induced and maintained with isoflurane; a catheter was placed in a cephalic vein for the administration of lactated Ringer's solution or remifentanil CRIs, and a catheter was placed in the jugular vein for collection of blood samples for blood gas analyses. On the first study day, individual basal MAC (MAC(Basal)) was determined for each cat. On the second study day, 3 remifentanil CRIs (0.25, 0.5, and 1.0 microg/kg/min) were administered (in ascending order); for each infusion, at least 30 minutes elapsed before determination of MAC (designated as MAC(R0.25), MAC(R0.5), and MAC(R1.0), respectively). A 15-minute washout period was allowed between CRIs. A control MAC (MAC(Control)) was determined after the last remifentanil infusion., Results: Mean +/- SD MAC(Basal) and MAC(Control) values at sea level did not differ significantly (1.66 +/- 0.08% and 1.52 +/- 0.21%, respectively). The MAC values determined for each remifentanil CRI did not differ significantly. However, MAC(R0.25), MAC(R0.5), and MAC(R1.0) were significantly decreased, compared with MAC(Basal), by 23.4 +/- 7.9%, 29.8 +/- 8.3%, and 26.0 +/- 9.4%, respectively., Conclusions and Clinical Relevance: The 3 doses of remifentanil administered via CRI resulted in a similar degree of isoflurane MAC reduction in adult cats, indicating that a ceiling effect was achieved following administration of the lowest dose.

The enzyme rhodanese (EC 2.8.1.1) is an ubiquitous enzyme which is present in all living organisms, from bacteria to man. It is speculated that this enzyme plays a central role in cyanide detoxification. However, its wide tissue distribution suggests this enzyme might perform other functions beside cyanide detoxification. Although the distribution of rhodanese in different tissues of human and domestic animals has been studied, little is known about the pattern of distribution and physiological roles of this enzyme in the cat. The purpose of this investigation was to determine the enzyme levels and compare the distribution of this enzyme in different tissues of the cat. A selection of tissue samples was assayed for rhodanese activity. The protein content of tissue extracts and enzymatic activities were calculated as units per gram tissue and units per milligram protein of the tissue. Results showed that in terms of units per milligram protein of the tissue (specific activity of the enzyme), colon and rectum mucosal layers and testis were the richest sources of the enzyme followed by ovary, mucosal layer of jejunum and liver. With respect to units/gram tissue, liver followed by testis, colon and rectum mucosal layers, ovary and mucosa of jejunum exhibited highest activities. The results of this study will allow one to speculate on the involvement of rhodanese in several biochemical and physiological functions in different tissues and organs of this species.

Impaired insulin sensitivity is increasingly recognised in cats, but sequences of genes involved in insulin-signalling are largely undetermined in this species. In this study, extended feline mRNA sequences were determined for the adiponectin, glucose transporter-1 (GLUT1), GLUT4, peroxisome proliferative activated receptor-gamma1 (PPARgamma1), PPARgamma2, plasminogen activator inhibitor-1 (PAI-1), monocyte chemoattractant protein-1 (MCP-1) and insulin receptor genes. Conserved dog-specific primers identified from human-dog mRNA alignments were used to amplify feline cDNA in the polymerase chain reaction (PCR). The feline sequences determined by this method were used to design feline-specific primers suitable for real-time PCR for quantification of gene expression in insulin sensitive tissues of healthy cats. Partial sequences of feline mRNAs had 86-95% identity with dog and human genes. Expression of adiponectin, GLUT1, GLUT4, PPARgamma1, PPARgamma2, PAI-1 and insulin receptor mRNA was detected and quantified in subcutaneous and visceral fat and skeletal muscle, whereas MCP-1 mRNA was detected in adipose tissue but not in skeletal muscle. Further characterisation of genes related to glucose metabolism in cats will provide additional insights into insulin-signalling mechanisms in this species.

In most mammals, glucokinase (GK) acts as a hepatic "glucose sensor" that permits hepatic metabolism to respond appropriately to changes in plasma glucose concentrations. GK activity is potently regulated by the glucokinase regulatory protein (GKRP), which is encoded by the GCKR gene. GKRP binds GK in the nucleus and inhibits its activity. GK becomes active when it is released from GKRP and translocates to the cytosol. Low glucokinase (GK) activity is reported to be a principal feature of feline hepatic carbohydrate metabolism but the molecular pathways that regulate GK activity are not known. This study examined the hypothesis that species-specific differences in GKRP expression parallel the low GK activity observed in feline liver. Hepatic GKRP expression was examined using RT-PCR, immunoblot, and confocal immunomicroscopy. The results show that the GCKR gene is present in the feline genome but GCKR mRNA and the GKRP protein were absent in feline liver. The lack of GKRP expression in feline liver indicates that the low GK activity cannot be the result of GKRP-mediated inhibition of the GK enzyme. However, the absence of the permissive effects of GCKR expression on GK expression and activity may contribute to reduced GK enzyme activity in feline liver. The study results show that the cat is a natural model for GCKR knockout and may be useful to study regulation of GCKR expression and its role in hepatic glucose-sensing and carbohydrate metabolism.

Robenacoxib is a new nonsteroidal anti-inflammatory drug (NSAID) developed for use in companion animal medicine. The objectives of this study were: to quantify the inhibitory actions of robenacoxib on cyclooxygenase (COX) isoenzymes in feline whole blood assays; to establish blood concentration-time profiles of robenacoxib after intravenous and subcutaneous dosing in the cat and; to predict the time courses of inhibition of COX isoforms by robenacoxib. COX-1 and COX-2 activities in heparinized feline whole blood samples were induced with calcium ionophore and lipopolysaccharide, respectively. Inhibition of thromboxane B2 provided a marker of both COX-1 and COX-2 activities and a nonlinear parametric mixed effects modelling approach was used to establish the pharmacodynamic parameters describing this inhibition. Mean values (and prediction intervals) of IC50 were 28.9 (16.4-51.1) microM (COX-1) and 0.058 (0.010-0.340) microM (COX-2). These parameters were used to compute several selectivity indices. Selectivity IC ratios (COX-1:COX-2) were 502.3 (IC50/IC50), 451.6 (IC95/IC95) and 17.05 (IC20/IC80). Based on a clinically recommended dosage regimen of 2 mg/kg, it was predicted that the corresponding mean robenacoxib blood concentration over the first 12 h after drug administration corresponded to 5% inhibition of COX-1 and 90% inhibition of COX-2.