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OBJECTIVE To measure the degree to which partial bladder outlet obstruction (PBOO) results in oxidative bladder damage, which subcellular components of the bladder are affected and whether these changes correlate with bladder function. MATERIALS AND METHODS In all, 32 rabbits were divided into four groups. Each group underwent PBOO for 1, 2, 4, and 8 weeks, respectively. Bladder tissue from each group was homogenized and separated into subcellular fractions via differential centrifugation. The carbonyl content within the subcellular fractions, including the nuclear, mitochondrial, and microsomal pellets, was then quantified by dot blot analysis. RESULTS Total bladder oxidation increased with duration of obstruction across all subcellular fractions. The largest increase in total oxidation occurred between 4 and 8 weeks. Protein oxidation density in the nuclear and microsomal fractions both showed increases at 2 weeks obstruction, decreases at 4 weeks, and then large increases at 8 weeks. The increase in protein oxidation density between 4 and 8 weeks obstruction was most pronounced in the microsomal fraction. CONCLUSIONS Overall bladder protein oxidation increased with the duration of obstruction and increased at a greater rate during the transition to decompensation. Furthermore, the subcellular fraction that exhibited the most oxidation was the microsomal pellet. The amount of protein oxidation correlated with the functional changes in the bladder.

OBJECTIVE To compare the physiological and structural changes after short-term partial bladder outlet obstruction (PBOO) in young and old rabbits, as PBOO results in marked contractile and histological alterations in the bladder. MATERIALS AND METHODS In all, 20 young (7–8-week-old) and 20 old (2 years old) male rabbits were divided into four subgroups of five each (four obstructed and one sham control rabbit). The rabbits in the groups were evaluated after 1, 3, 7 and 14 days of PBOO, respectively. At the end of the respective periods, cystometry and contractile responses to field stimulation (FS), ATP, carbachol and potassium chloride were determined. Full-thickness sections of the bladder body and base were used to determine the vascular density, nerve density and smooth muscle/collagen ratios. RESULTS The bladder weight of young rabbits increased at 1–7 days of PBOO and returned toward control levels at 14 days of PBOO, while in old rabbits it was higher than the control during the entire experiment. For the young rabbits, the responses to field stimulation decreased progressively for 1, 3 and 7 days, and increased significantly at 14 days. For old rabbits there was a progressive decrease to a minimal response by 3 days of PBOO and the response remained at this level over 14 days. The contractile response to ATP, carbachol and KCl were similar to the responses to FS. The vascular density in both groups increased to a maximum at 7 days and then decreased toward control values at 14 days. For the young rabbits, nerve density decreased more than in old rabbits. In the old group, the smooth muscle/collagen ratio was increased throughout PBOO and was higher than in young rabbits. The connective tissue compartment was markedly greater than in the young rabbits and the basal mucosa had vacuoles which were not apparent in the young bladders. CONCLUSIONS This study shows that the adaptive changes to PBOO are faster in young rabbit bladders than in older rabbits.

OBJECTIVE To investigate the potential protective effect of a grape suspension in a rabbit model of in vivo bilateral ischaemia/reperfusion (I/R), which is a causal factor in obstructive bladder dysfunction. MATERIALS AND METHODS Six groups of four New Zealand White rabbits were treated by twice-daily gavage with aqueous grape suspension (groups 1–3) or sugar-water vehicle (groups 4–6) for 3 weeks. Groups 1 and 4 then received bilateral ischaemia for 2 h, and groups 2 and 5 received bilateral ischaemia for 2 h and reperfusion (recovery) for 1 week. Groups 3 and 6 were controls (sham-operated). The effects on cystometry, in vitro contractile responses, and morphology were evaluated. RESULTS Ischaemia resulted in significant reductions in the contractile responses to all forms of stimulation in vehicle-fed rabbits, whereas there were no reductions in grape-fed rabbits. Contractile responses were significantly reduced in both I/R groups, but significantly more in vehicle-fed than in grape-fed rabbits. Immunohistochemical studies showed less hypoxia in the bladders of grape-fed rabbits than in vehicle-fed rabbits for both ischaemia-only and I/R groups. CONCLUSIONS Feeding rabbits with grape suspension provided significant protection against the hypoxic effects of bilateral ischaemia and I/R.

OBJECTIVE To evaluate the effects of ovariectomy (Ovx) and oestrogen therapy on the free fatty acid (FFA) content, endogenous lipase activity, and the phospholipid (PL) content of the urinary bladder, as reduced circulating oestrogen during and after the menopause has been linked to various bladder dysfunctions including incontinence and recurrent urinary tract infections. MATERIALS AND METHODS In all, 12 New Zealand White female rabbits were separated into three groups; the Ovx + oestrogen group received Ovx and treatment with conjugated β-oestradiol (3 weeks), the Ovx group received Ovx and vehicle (3 weeks), and the control group received sham operation and vehicle. Cystometry was used to evaluate compliance and in vitro muscle strip studies quantified contractility. For the bulk of the bladder, the muscle and mucosa were separated; FFA and PL concentrations were analysed using standard biochemical techniques. RESULTS The bladder contractile responses and compliance decreased after Ovx and returned to or above normal after oestrogen administration. Both FFA and PL concentrations of the mucosa were about three times greater than that of the smooth muscle. Ovx significantly reduced the FFA and PL concentrations of both muscle and mucosa, while oestrogen therapy restored them to normal. CONCLUSIONS Reduced FFA and PL content of the smooth muscle membranes would decrease their fluidity and contribute to decreased compliance and contractility. Reduced FFA and PL content of the mucosa would be consistent with mucosal damage and may contribute to the increased incidences of incontinence and bladder infection.

OBJECTIVE To investigate the use of free-radical generation as a result of protein carbonylation and nitrotyrosination to characterize the level of bladder dysfunction after partial bladder outlet obstruction (PBOO) and reversal. MATERIALS AND METHODS We surgically created PBOO in male New Zealand White rabbits; after 4 weeks of PBOO, one group of six rabbits was assessed, while the PBOO was relieved in two additional groups of six rabbits each that were assessed at 4 and 8 weeks after relieving the PBOO. Six sham-operated rabbits served as controls. Sedated rabbits were assessed by cystometry and the bladders were then removed for contractile, histological and molecular studies. Western blotting was used to determine the level of carbonylation and nitrotyrosination at the protein level. RESULTS The PBOO group had significant decreases in the contractile responses to field stimulation, ATP, carbachol and KCl. The responses to all forms of stimulation increased significantly at 4 weeks after reversal, and further increased to near normal levels by 8 weeks. Similarly, compliance and cystometric values also returned to near normal values after reversal. The hypertrophied smooth muscle of the obstructed bladders regressed to near-normal size. There was a significant increase in the level of carbonylation and nitrotyrosination after PBOO, and a progressive decrease in the 4-week reversal groups, nearing control values by 8 weeks. CONCLUSIONS Significantly increased carbonylation and nitrotyrosination levels after PBOO correlated with the severe dysfunction in the obstructed rabbits. Similarly, decreased levels of oxidation and nitration correlated with the functional recovery after reversal.

OBJECTIVE To investigate the effect of letrozole (a potent aromatase inhibitor that effectively inhibit the synthesis of oestrogen) on bladder contraction with changes in morphology and biochemistry. MATERIALS AND METHODS Sixteen female New Zealand white rabbits were separated into four equal groups; groups 1–3 were given oral letrozole for 1, 2 and 3 weeks, and group 4 was given saline and served as the control group. At the end of the medication period each rabbit was anaesthetized and the bladder muscle strips were used for contractile, histological and biochemical studies. RESULTS The concentration of serum oestrogen was significantly lower and testosterone was significantly higher in letrozole-treated rabbits than in the control group. The rabbits treated for 1 week with letrozole showed significant decreases in the contractile responses to electrical field stimulation, ATP and carbachol, but not to KCl. Contractility returned to normal in the rabbits treated for 2 and 3 weeks. Letrozole resulted in an increased volume percentage of collagens and decreased bladder compliance. The volume percentage of the smooth muscle component also changed, with a significant decrease at 1 week and then a gradual increase at 2 and 3 weeks. Contractile dysfunction was absent at 2 and 3 weeks, which was consistent with no change in sarcoplasmic reticulum Ca2+-ATPase content or mitochondrial function. CONCLUSIONS The bladder contractility decline in the first week and was restored at 2 and 3 weeks. The present study unexpectedly showed the possibility that testosterone might be as important as oestrogen in the contractile function of the female bladder.

OBJECTIVE To evaluate the effect of maturation and ageing on oestrogen-induced functional hypertrophy of the female rabbit bladder. MATERIALS AND METHODS Twenty female rabbits were separated into two groups of 10 each by age, young (immature) and old rabbits and each age group was subdivided into three subgroups. The rabbits in subgroup 1 were controls, subgroup 2 were ovariectomized (Ovx) and subgroup 3 were Ovx and received 17-β oestradiol (1 mg/kg/day) by a subcutaneous slow-release tablet implant. After 15 days of treatment, the rabbits were killed, the bladder was excised, and the body and base separated; two full-thickness longitudinal strips from the ventral surface of the bladder body, and one full-thickness strip from the base, were prepared for contractile studies. The contractile responses to electrical-field stimulation, carbachol, ATP and KCl were determined for both the bladder body and base strips. In addition, full-thickness strips of bladder body and base were fixed in formalin for histological and immunohistological studies. RESULTS Ovx plus oestradiol resulted in significant increases in bladder weight and responses to all forms of stimulation in young and old rabbits (except for the response to KCl). Vascular density and the smooth muscle (SM)/collagen ratio significantly increased after oestradiol replacement. Interestingly, the increase in vascular density was greater in the young than in the old rabbits. CONCLUSIONS The present study shows that oestrogen supplementation mediates a functional hypertrophy characterized by increased contractile responses to all forms of stimulation in both young and old rabbits. The increased contractile responses might be explained by the increases in vascular density and SM/collagen ratio.