Search

Aims: Spontaneous Ca 2+ release leads to afterdepolarizations and triggered arrhythmia in catecholaminergic polymorphic ventricular tachycardia (CPVT). Irregular Ca 2+ release is hypothesized to manifest as slowed depolarization and irregular repolarization. Our goal was to study depolarization and repolarization abnormalities in CPVT, as they remain largely uninvestigated., Methods and Results: We studied intracellular Ca 2+ handling and action potentials (APs) in an induced pluripotent stem cell (iPSC) model of CPVT. Induced pluripotent stem cell cardiomyocytes from a RyR2-P2328S patient showed increased non-alternating variability of Ca 2+ transients in response to isoproterenol. β-Agonists decreased AP upslope velocity in CPVT cells and in monophasic AP recordings of CPVT patients. We compared 24 h electrocardiograms (ECGs) of 19 CPVT patients carrying RyR2 mutations and 19 healthy controls. Short-term variability (STV) of the QT interval was 6.9 ± 0.5 ms in CPVT patients vs. 5.5 ± 0.4 ms in controls (P < 0.05) and associated with a history of arrhythmic events. Mean T-wave alternans (TWA) was 25 ± 1.4 µV in CPVT patients vs. 31 ± 2.0 µV in controls (P < 0.05). Older CPVT patients showed lower maximal upslope velocity of the ECG R-spike than control patients., Conclusion: Catecholaminergic polymorphic ventricular tachycardia patients show higher STV of repolarization but lower TWA on the 24 h ECG than control patients, which is likely to reflect increased non-alternating variability of Ca 2+ release by mutant RyR2s as observed in vitro. β-Agonists slow depolarization in RyR2-mutant cells and in CPVT patients. These findings may constitute a marker of arrhythmogenicity., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.)

Objective: Generalized glucocorticoid resistance is characterized by impaired cortisol signaling, resulting from mutations of the glucocorticoid receptor (GR) gene NR3C1. The objective of our study was to identify the causative mutation in a patient with clinical manifestations compatible with generalized glucocorticoid resistance and to determine the functional consequences of the mutation. The possible occurrence of NR3C1 mutations in a selected group of hypertensive subjects with low plasma renin and aldosterone levels was also explored., Patients: The proband, a male athlete, was diagnosed with hypertension associated with low plasma renin activity and low serum aldosterone concentration at the age of 27 years. Liddle's syndrome was suspected and the patient was treated with amiloride with initial success. Subsequent examinations revealed elevated serum cortisol and ACTH levels, with resistance to suppression with low doses of dexamethasone. After identification of an NR3C1 mutation in the proband, the available family members and 51 nonrelated hypertensive subjects with low plasma renin and aldosterone concentrations were also studied., Results: A two-nucleotide deletion in exon 9α, predicted to cause a frameshift mutation (p.L773VfsX25) in the hormone-binding domain of the GR, was identified in the patient in a heterozygous form. Affected brother and father died of premature coronary heart disease. Functional studies in COS-1 cells showed that this mutation eliminates both ligand-binding and transactivation ability of the receptor. No pathogenic NR3C1 mutations were identified in 51 unrelated hypertensive patients with low plasma renin and aldosterone levels., Conclusion: We identified a novel frameshift mutation in NR3C1 as the cause of glucocorticoid resistance. The mutation eliminates the functional activity of the GR, as studied by in vitro experiments. Mutations in NR3C1 do not seem to be common causes for hypertension with low renin and aldosterone levels.

Background: Human polymorphisms affecting gut epithelial barrier and interactions with bacteria predispose to the inflammatory bowel diseases (IBD) Crohn's disease (CD) and ulcerative colitis (UC). The intestinal transporter PepT1, encoded by the SLC15A1 gene, mediates intracellular uptake of bacterial products that can induce inflammation and NF-kappaB activation upon binding to NOD2, a protein often mutated in CD. Hence, we tested SLC15A1 polymorphisms for association with IBD., Methods: Twelve SLC15A1 single nucleotide polymorphisms (SNPs) were genotyped in 1783 individuals from 2 cohorts of Swedish and Finnish IBD patients and controls. An in vitro system was set up to evaluate the potential impact of SLC15A1 polymorphism on PepT1 transporter function by quantification of NOD2-mediated activation of NF-kappaB., Results: The common allele (C) of a coding polymorphism (rs2297322, Ser117Asn) was associated with CD susceptibility both in Sweden and in Finland, but with genetic effects in opposite directions (risk and protection, respectively). The best evidence of association was found in both populations when the analysis was performed on individuals not carrying NOD2 common risk alleles (Sweden allelic P = 0.0007, OR 1.97, 95% confidence interval [CI] 1.34-2.92; Finland genotype P = 0.0013, OR 0.63, 95% CI 0.44-0.90). The PepT1 variant encoded by the C allele (PepT1-Ser117) was associated with reduced signaling downstream of NOD2 (P < 0.0001 compared to Pept1-Asn117)., Conclusions: A functional polymorphism in the SLC15A1 gene might be of relevance to inflammation and antibacterial responses in IBD. Whether this polymorphism truly contributes to disease susceptibility needs to be further addressed, and should stimulate additional studies in other populations.

Background: Polymorphisms in genes coding for components of the renin-angiotensin system (RAS) and alpha-adducin (ADD1) have been reported to be associated with blood pressure (BP) responses to antihypertensive agents. The results, however, have not been consistent and most of the earlier studies have been small and lacked placebo-control. Therefore, the association of common polymorphisms in these genes with BP responses to four different antihypertensive drugs was analyzed in a controlled study., Methods: The study included 208 hypertensive Finnish men from the GENRES study. All of them used amlodipine 5 mg, bisoprolol 5 mg, hydrochlorothiazide (HCT) 25 mg, and losartan 50 mg daily, each for 4 weeks as a monotherapy in a double-blind, randomized, study. The treatment periods were separated by 4-week placebo periods. Both 24-h ambulatory (ABP) and office BP (OBP) measurements were carried out. The polymorphisms analyzed were ADD1 Gly460Trp, angiotensinogen (AGT) Met235Thr, angiotensin converting enzyme (ACE) insertion/deletion (I/D), and angiotensin II type 1 receptor (AGTR1) 1166A/C., Results: The presence of 460Trp allele of ADD1, previously suggested to be a marker of thiazide responsiveness, did not predict a better response to HCT. There was no significant association of AGT Met235Thr, ACE I/D, and AGTR1 1166A/C polymorphisms with BP responses to the study drugs. ADD1 460Trp and AGT 235Thr alleles were associated with higher systolic white coat effect (WCE) during the placebo periods (P values 0.03 and 0.01, respectively)., Conclusions: Common polymorphisms of ADD1, AGT, ACE, and AGTR1 do not markedly predict BP responses to amlodipine, bisoprolol, HCT, and losartan, at least in white hypertensive men.

Background: Crohn's disease (CD) and ulcerative colitis (UC), 2 major forms of inflammatory bowel disease (IBD), are complex disorders with significant genetic predisposition. The first CD-associated gene, CARD15/NOD2, was recently identified and since then several reports on novel IBD candidate genes have emerged. We investigated disease phenotype association to genetic variations in IL23R, ATG16L1, DLG5, ABCB1/MDR1, TLR4, TNFRSF1A, chromosome 5 risk haplotype including SLC22A4 and SLC22A5, and HLA-DRB1*0103 allele among Finnish IBD patients., Methods: A total of 699 IBD patients were genotyped for disease-associated variants by polymerase chain reaction (PCR) and restriction enzyme digestion or Sequenom iPLEX method., Results: Five markers spanning the IL23R gene were associated with CD. The SNP (single nucleotide polymorphism) rs2201841 gave the strongest association (P = 0.002). The rare HLA-DRB1*0103 allele was found to associate with UC (P = 0.008), and the TNFRSF1A A36G variant was associated with familial UC (P = 0.007). Upon phenotypic analysis we detected association between familial UC and rare TNFRSF1A alleles 36G and IVS6+10G (P = 0.001 and P = 0.042, respectively). In addition, IL23R markers were associated with stricturing CD (P = 0.010-0.017), and ileocolonic CD was more prevalent in the carriers of the same 2 TNFRSF1A variants (P = 0.021 and P = 0.028, respectively). Less significant genotype-phenotype associations were observed for the TLR4 and HLA variants., Conclusions: We were able to replicate the association of the IL23R variants with CD as well as HLA-DRB1*0103 with UC; confirmation of TNFRSF1A association with UC needs additional studies. Our findings also suggest that polymorphisms at IL23R and TNFRSF1A, and possibly HLA and TLR4, loci may account for phenotypic variation in IBD.

Background: Three mutations (R702W, G908R, and 1007fs) of the CARD15/NOD2 gene associate with Crohn's disease (CD). Despite a strong linkage of CD to the inflammatory bowel disease (IBD) 1 region, only 16% of the Finnish CD patients carry 1 of these 3 mutations, pointing to the possibility of yet undetected founder mutations in the genetically isolated Finns. The aim of this study was to screen for CARD15 mutations in Finnish CD patients and to assess their functional consequences and relation to clinical phenotype., Methods: We performed CARD15 mutation screening in 240 CD probands. For functional studies, blood mononuclear cells were cultured alone or with muramyl dipeptide (MDP) and IL-8 levels were determined., Results: We identified 30 different variants, including 12 new ones. Allele frequencies for the R702W, G908R, and 1007fs mutations were 3.3%, 0.4%, and 4.8%, respectively. The 1007fs variant was the only 1 associated significantly with CD. Five novel variants (R38M, W355X, P727L, W907R, R1019X) were found in 5 patients. The biochemical nature of these new mutations, data obtained by cross-species comparisons, as well as low IL-8 production favors their pathogenic role. All 5 patients with novel mutations presented a complicated form of ileal or ileocolonic disease., Conclusions: In conclusion, we identified 5 novel CARD15 mutations with an apparent pathophysiological role, but could not identify a putative Finnish founder mutation. It is still possible that regulatory mutations present in the flanking or intronic areas of the CARD15 gene contribute to the genetic susceptibility of CD. Homozygosity or compound heterozygosity for CARD15 gene mutations must be considered especially in complicated CD patients.

Aims: Mutations in cardiac ryanodine receptors (RyR2s) are linked to catecholaminergic polymorphic ventricular tachycardia (CPVT), characterized by risk of polymorphic ventricular tachyarrhythmias and sudden death during exercise. Arrhythmias are caused by gain-of-function defects in RyR2, but cellular arrhythmogenesis remains elusive., Methods and Results: We recorded endocardial monophasic action potentials (MAPs) at right ventricular septum in 15 CPVT patients with a RyR2 mutation (P2,328S, Q4,201R, and V4,653F) and in 12 control subjects both at baseline and during epinephrine infusion (0.05 microg/kg/min). At baseline 3 and during epinephrine infusion, four CPVT patients, but none of the control subjects, showed delayed afterdepolarizations (DADs) occasionally coinciding with ventricular premature complexes. In order to study the underlying mechanisms, we expressed two types of mutant RyR2 (P2,328S and V4,653F) causing CPVT as well as wild-type RyR2 in HEK 293 cells. Confocal microscopy of Fluo-3 loaded cells transfected with any of the three RyR2s showed no spontaneous subcellular Ca(2+) release events at baseline. Membrane permeable cAMP analogue (Dioctanoyl-cAMP) triggered subcellular Ca(2+) release events as Ca(2+) sparks and waves. Cells expressing mutant RyR2s showed spontaneous Ca(2+) release events at lower concentrations of cAMP than cells transfected with wild-type RyR2., Conclusion: CPVT patients show DADs coinciding with premature action potentials in MAP recordings. Expression studies suggest that DADs are caused by increased propensity of abnormal RyR2s to generate spontaneous Ca(2+) waves in response to cAMP stimulation. Increased sensitivity of mutant RyR2s to cAMP may explain the occurrence of arrhythmias during exercise or emotional stress in CPVT.

Background: Only a minority of hypertensive individuals is adequately controlled for their hypertension, partially because reliable predictors for efficient antihypertensive drug therapy are lacking., Methods: In a prospective, randomized, double-blind, cross-over, placebo-controlled study (The GENRES Study), 208 moderately hypertensive Finnish men (aged 35 to 60 years) were treated for 4 weeks with antihypertensive drugs from four different classes: amlodipine (5 mg), bisoprolol (5 mg), hydrochlorothiazide (25 mg), or losartan (50 mg) daily. Each individual received each of the four monotherapies in a randomized order. Four-week placebo periods were included before and between drug treatment periods. Antihypertensive responses were assessed with 24-h ambulatory and office measurements and analyzed according to age, body mass index, triceps skin fold thickness, waist-to-hip ratio, duration of hypertension, number of previous antihypertensive drugs, number of affected parents, and blood pressure (BP) levels, and profiles during placebo periods., Results: The median BP responses in 24-h ambulatory recordings (systolic/diastolic) were 11/8 mm Hg for bisoprolol, 9/6 mm Hg for losartan, 7/5 mm Hg for amlodipine, and 5/2 mm Hg for hydrochlorothiazide. The highest pairwise within-subject correlations in BP responses were seen for the combinations of bisoprolol-losartan and amlodipine-hydrochlorothiazide. The BP responses to bisoprolol and losartan did not vary according to the variables. Amlodipine and hydrochlorothiazide responses were positively correlated with age, placebo BP level, and lower night-time dipping on placebo., Conclusions: Baseline clinical and BP parameters may be used to predict the efficacy of antihypertensive therapies. The GENRES Study material should provide an excellent platform for future pharmacogenetic analyses of antihypertensive drug responsiveness.

Two Finnish cohorts, comprising 56 children with severe early-onset obesity (relative weight for height greater than or equal to +70% before age 10) and 252 morbidly obese adults (body mass index, > or = 40 kg/m(2)), were screened for melanocortin-4 receptor (MC4R) mutations. We identified a pathogenic mutation (S127L) in one child, causing severe early-onset obesity. We describe the phenotype of this particular mutation for the first time. We also identified a novel (I226T) polymorphism in the coding and two new variations (-439delGC and 1059C>T) outside the coding region of the MC4R gene. Three previously described polymorphisms (V103I, T112M, and I125L) were identified. In vitro functional studies of variants T112M, S127L, and I226T supported a pathogenic role of the S127L mutation, because signaling properties of the receptor in response to the MC4R agonists alpha-MSH, beta-MSH, and gamma(1)-MSH were impaired. The S127L mutation did not affect receptor inhibition by the antagonist agouti-related protein. Localization of the three variant receptors was similar to that of wild type. In conclusion, a pathogenic MC4R mutation was found among subjects with severe early-onset obesity but not among morbidly obese adults. Impaired function of the S127L receptor was due to reduced activation, not a defect of protein transport to the cell membrane.

Obesity is a multifactorial trait with evidence of a genetic component. Obesity is very common in all westernized countries, including Finland, where 10% of the adult population has a body mass index of 32 kg/m2 or more. Here we report results from a three-stage genome-wide scan of obesity in 188 affected subjects (body mass index, > or =32 kg/m2) from 87 Finnish families. Initially, 374 markers with an average density of 10 centimorgans were genotyped. The strongest evidence for linkage to obesity was detected on chromosome Xq24, with the marker DXS6804 providing a maximum likelihood score (MLS) 3.14 in a model-free 2-point sibpair analysis. Fine-mapping in an extended sample set of 367 affected subjects from 166 families yielded a multipoint MLS of 3.48 over this X-chromosomal region. The Xq24 region contains a plausible candidate gene, serotonin 2C receptor, variants of which have been shown to predispose to obesity and type II diabetes in mice. Another chromosomal region also provided suggestive evidence of linkage, an area on 18q21, flanking the melanocortin-4 receptor, where a 2-point MLS of 2.42 with marker D18S1155 was obtained with a set of 367 affected subjects. In conclusion, our results in this Finnish study sample suggest that a locus on chromosome Xq24 influences the risk of obesity.

Earlier epidemiologic studies have yielded inconsistent results on the extent and timing of the blood pressure (BP) increase in offspring of hypertensive parents. We hypothesized that a familial influence on the BP of the offspring exists from birth on, but becomes significant only later in childhood. We studied the influence of familial occurrence of hypertension on the BP of 3596 children aged 6 to 18 years during a 6-year follow-up. In addition, we examined the possible associations of BP variations with polymorphisms of two candidate genes for hypertension, ie, those coding for the angiotensin converting enzyme (ACE) and those coding for angiotensinogen. A positive family history of hypertension was reflected as the occurrence of higher systolic BP values from the age of 9 years and upward among the females and from the age of 12 years and upward among the males. The mean differences in BP varied from 3.2 to 5.8 mm Hg (systolic) and 2.1 to 5.9 mm Hg (diastolic) between the female offspring of normotensive and hypertensive parents and grandparents. The systolic BP values were significantly higher among females with a hypertensive history in two generations in comparison with females from normotensive families. Among the male offspring of hypertensive and normotensive families, the BP differences were inconsistent. The deletion/deletion males had higher systolic BP values than those with other ACE genotypes. In contrast, variation at the angiotensinogen gene locus was not significantly associated with BP. We conclude that parental history of hypertension is a risk factor for high blood pressure among the offspring from the ages of 9 to 12 years and upward, and hypertension within two generations may enhance this effect. Although the common genetic variation of ACE may influence blood pressure in male children and adolescents, our data do not suggest a role for the common variation of the angiotensinogen gene as a BP regulator during childhood.

Leptin is an adipocyte-derived peptide hormone regulating energy balance in experimental animals. Although the physiological function of leptin in humans is still unclear, its secretion is closely related to fat mass in adult humans. To examine how fetal growth correlates with leptin levels at birth, an umbilical cord venous blood sample was obtained at the delivery from 50 term newborn infants. Twenty-eight of the newborn infants had birth weights appropriate for gestational age (AGA; mean +/- SEM, 3362 +/- 90 g; relative birth weight, -0.08 +/- 0.2 SD), 9 were large for gestational age (birth weight, 4655 +/- 165 g; relative birth weight, 3.2 +/- 0.3 SD; P < 0.001 vs. AGA newborn infants), and 13 were small for gestational age (SGA; birth weight, 2385 +/- 69 g; relative birth weight, -2.2 +/- 0.08 SD; P < 0.001 vs. AGA newborn infants). Leptin concentrations were higher in large for gestational age (35.7 +/- 8.0 micrograms/L; P < 0.005), but lower in SGA (3.3 +/- 0.5 micrograms/L; P < 0.001) than in AGA infants (14.5 +/- 2.8 micrograms/L). When adjusted for differences in body weight, mean leptin levels were similar in the three newborn groups. Leptin concentration correlated closely with both absolute and relative birth weights (r = 0.71; P < 0.001 in both), with cord blood insulin concentration (r = 0.67; P < 0.001), and with placental weight (r = 0.60; P < 0.001). These data suggest that leptin is synthesized in utero, and that the circulating leptin concentration relates to the intrauterine growth pattern.

Three common alleles determine six apolipoprotein E (apo E) phenotypes that are associated with variations in serum cholesterol in the population. This genetic variation results from single nucleotide alterations at two DNA loci encoding the amino acid residues 112 and 158 of apo E. We compared results of apo E phenotyping carried out by isoelectric focusing with those of apo E genotyping accomplished by direct DNA analysis. In the latter, the target DNA was amplified by the polymerase chain reaction (PCR) and subsequently analyzed by digestion with the restriction enzyme Hha I, followed by polyacrylamide gel electrophoresis of the cleavage products. With one exception, these two techniques yielded similar results from all 40 samples tested. In addition, a rare variant form of apo E (phenotype E1) was analyzed separately and incorrectly diagnosed as E2 by the Hha I digestion method; the anticipated mutation in the codon 127 was, however, confirmed by demonstration of a new Taq I restriction site in this variant gene. These data confirm that the common isoforms of apo E usually arise from genetic variation of the codons 112 and 158 and demonstrate the feasibility of the PCR technique in apo E genotyping.

We used a modification of the polymerase chain reaction (PCR), involving two pairs of oligonucleotide primers, to detect a mutation in the low-density lipoprotein (LDL) receptor gene, commonly occurring among patients with familial hypercholesterolemia (FH) in Finland. This mutation, called FH-Helsinki, involves a large (about 9500 base pairs, bp) deletion in the LDL receptor gene extending from intron 15 to exon 18. For the PCR, one pair of primers was designed to cover both sides of the deletion in its immediate vicinity. In the presence of the deletion, the primers were brought close enough to each other to allow the amplification and electrophoretic detection of a 300-bp amplification product. In the absence of the deletion, no amplification occurred and this band accordingly was not visible in the gel. To render the interpretation of the results unequivocal, we designed a second pair of oligonucleotide primers. This pair of primers allowed another amplification product (158 bp) to appear in samples containing a normal exon 17, i.e., in DNA specimens from healthy subjects and FH heterozygotes with or without the FH-Helsinki deletion. The technique is easy to perform, avoids the use of radioactive reagents, and is applicable to the detection of any extensive DNA deletion.

Circulating human lymphocytes contain glucocorticoid receptors (GR). To see if adrenocortical imbalance is associated with changes in the level of GR, several patients with hypo- and hypercortisolism were studied. Peripheral lymphocytes were prepared by Ficoll-Hypaque gradients and were then subjected to a whole cell-binding assay measuring the total cellular receptor pool, with [3H]dexamethasone as the ligand. There were no significant differences in the cellular content of GR among healthy controls, 10 patients with Cushing's syndrome, and 3 patients suffering from Addison's disease; the absolute levels of GR were 4850 +/- 1340, 4900 +/- 2160, and 5640 +/- 1110 (mean +/- SD) receptors/cell, respectively. The mean equilibrium dissociation constants of the interaction of [3H]dexamethasone with the receptor were also about the same in the 3 groups (1-2 X 10(-8) M). Thus, aberrations in glucocorticoid balance strong enough to produce clear-cut clinical symptoms do not result in major alterations in the level of the peripheral GR. We also studied an additional patient who had hypercortisolism due to an adrenal adenoma but only slight clinical signs of hypercortisolism; interestingly, her cellular GR level was only 30% of normal. The lymphocytic GR content was also below normal in 2 patients with anorexia nervosa.

Glucocorticoids have been postulated to directly inhibit adrenocortical steroid production in laboratory animals. To investigate this in the human, we measured specific [3H]dexamethasone-binding sites in cytosol samples from normal and neoplastic human adrenal tissues. All nine normal adrenocortical samples, six adenomas (four cortisol-producing and two aldosterone-producing), and two hyperplastic adrenocortical samples studied were devoid of measurable specific glucocorticoid-binding activity. In contrast, steroid binding with characteristics of the glucocorticoid receptor (concentration of binding sites, 32-146 fmol/mg cytosol protein; Kd, 1.7-3.1 X 10(-9) M) was readily detectable in cytosol of all three adrenocortical carcinomas and all three pheochromocytomas examined. To elucidate the in vivo role of glucocorticoids as direct regulators of adrenocortical function, five patients with hypopituitarism receiving varying oral maintenance doses of dexamethasone were given ACTH iv. Increasing the orally administered dexamethasone dose from 1 to 8 mg/day did not alter the plasma cortisol response to a 4-h infusion of 250 micrograms synthetic ACTH in these patients. Collectively, these data cast doubt on the proposal that synthetic glucocorticoids directly suppress adrenocortical function in the human. Whether glucocorticoid receptors in tumor tissue could mediate the dexamethasone-induced suppression of hypercortisolism occasionally reported in patients with adrenocortical neoplasia remains to be investigated.

The mechanisms by which nonsteroidal antiandrogens such as flutamide (alpha, alpha, alpha-trifluoro-2-methyl-4'-nitro-m-propionotoluidide) influence androgen receptor distribution and androgen-regulated gene expression are poorly understood. Therefore, we studied acute and long-term effects of flutamide, administered alone or in combination with testosterone, on androgen receptor dynamics in mouse kidney. Nuclear androgen receptors were measured using 5 mM pyridoxal 5'-phosphate extracts of renal nuclei isolated with the hexylene glycol method. Androgen-regulated ornithine decarboxylase (ODC) and ODC-messenger RNA were used as biological markers for hormone action. A single dose of flutamide increased the measurable concentration of renal nuclear androgen receptors in a dose-dependent manner by 1 h after treatment, although to a lesser extent than a comparable dose of testosterone. When 5 mg flutamide was given concomitantly with a submaximal dose of testosterone (0.1 mg), nuclear androgen receptor concentration was similar to that achieved with flutamide alone; this inhibitory effect of the antiandrogen was reversed by a 10-fold higher dose of testosterone. The influence of flutamide on the steady-state receptor levels in renal nuclei achieved by continuous androgen administration was investigated by giving a single dose of this compound to mice with testosterone-releasing implants. In these animals, flutamide administration decreased nuclear androgen receptor concentration with an initial half-life of about 3.3 h. This half-life was similar to that after cycloheximide administration, but significantly longer than that measured (1.3 h) upon removal of the implant. During treatment of female mice for 8 days with testosterone-releasing implants (40 micrograms/day), both the immunoreactive and catalytically active ODC concentration increased about 300-fold. In contrast, there was no stimulation of ODC during the prolonged administration of flutamide, although this treatment resulted in a dose-dependent increase in the nuclear androgen receptor concentration. However, flutamide (up to 650 micrograms/day) given concomitantly with testosterone (40 micrograms/day) almost completely abolished the testosterone-induced increase in ODC. The changes in ODC-messenger RNA concentration, as measured by hybridization to a complementary DNA probe, paralleled those of the enzyme protein suggesting that flutamide action involves inhibition of transcription of androgen-regulated gene(s). We conclude that 1) nuclear androgen receptor turnover in mouse kidney is a relatively rapid process and 2) nonsteroidal antiandrogens such as flutamide have an intrinsic ability to form