Comparative response of rabbit bladder smooth muscle and mucosa to anoxia

Metabolic Stress-Induced Activation of AMPK and Inhibition of Constitutive Phosphoproteins Controlling Smooth Muscle Contraction: Evidence for Smooth Muscle Fatigue?

Metabolic stress diminishes smooth muscle contractile strength by a poorly defined mechanism. To test the hypothesis that metabolic stress activates a compensatory cell signaling program to reversibly downregulate contraction, arterial rings and bladder muscle strips in vitro were deprived of O₂ and glucose for 30 and 60 min (“starvation”) to induce metabolic stress, and the phosphorylation status of proteins involved in regulation of contraction and metabolic stress were assessed in tissues under basal and stimulated conditions. A 15–30 min recovery period (O₂ and glucose repletion) tested whether changes induced by starvation were reversible. Starvation decreased basal phosphorylation of myosin regulatory light chain (MLC-pS19) and of the rho kinase (ROCK) downstream substrates cofilin (cofilin-pS3) and myosin phosphatase targeting subunit MYPT1 (MYPT1-pT696 and MYPT1-pT853), and abolished the ability of contractile stimuli to cause a strong, sustained contraction. Starvation increased basal phosphorylation of AMPK (AMPK-pT172) and 3 downstream AMPK substrates, acetyl-CoA carboxylase (ACC-pS79), rhoA (rhoA-pS188), and phospholamban (PLB-pS16). Increases in rhoA-pS188 and PLB-pS16 would be expected to inhibit contraction. Recovery restored basal AMPK-pT172 and MLC-pS19 to control levels, and restored contraction. In AMPKα₂ deficient mice (AMPKα2-/-), the basal level of AMPK-pT172 was reduced by 50%, and MLC-pS19 was elevated by 50%, but AMPKα2-/- did not prevent starvation-induced contraction inhibition nor enhance recovery from starvation. These results indicate that constitutive AMPK activity participates in constitutive regulation of contractile proteins, and suggest that AMPK activation is necessary, but may not be sufficient, to cause smooth muscle contraction inhibition during metabolic stress.

The Ameliorating Effect of Exogenous Melatonin on Urinary Bladder Function in Hyperosmolar Bladder Overactivity and its Influence on the Autonomic Nervous System Activity

This study was designed to investigate the effects of melatonin on the bladder hyperactivity in hyperosmolar-induced overactive bladder (OAB) rats. Additionally, the influence of melatonin on the autonomic nervous system (ANS) using heart rate variability (HRV) analysis was assessed. 40 rats were divided into four groups: I – control (n=12), II – rats with hyperosmolar OAB (n=6), III – rats with melatonin pretreatment and hyperosmolar OAB (n=6) and IV – control with melatonin pretreatment (n=6). In group III and IV melatonin in dose of 100 mg/kg was given. HRV measurements in 10 rats, as follow: control (n=2), control after melatonin treatment (n=2), rats with hyperosmolar OAB without (n=3), and after (n=3) melatonin treatment were conducted. This study demonstrates marked influence of melatonin on urinary bladder activity in hyperosmolar-induced OAB rats. These rats showed significantly reduced the detrusor motor overactivity resulting in the improvement of cystometric parameters after melatonin treatment when compared to the control, as follow: a significant increase of intercontraction interval (70 %) and functional bladder capacity (67 %), as well as a decrease of the basal pressure, detrusor overactivity index and motility index of 96 %, 439 % and 40 %, respectively. ANS activity analysis revealed sympathetic overactivity in OAB rats, and parasympathetic superiority in melatonin treated OAB rats. Melatonin treatment in rats with hyperosmolar OAB (group III) caused significant increase of nuHF parameter (from 51.00 ± 25.29 to 76.97 ± 17.43), as well as a decrease of nuLF parameter (from 49.01 ± 25.26 to 23.03 ± 17.43) and LF/HF ratio (from 1.280 ± 0.980 to 0.350 ± 0.330). In conclusion, melatonin suppresses hyperosmolar OAB, and modulates ANS activity by inhibition of the sympathetic drive. Therefore, melatonin may become a useful agent for OAB management.

Effect of severity and duration of bladder outlet obstruction on catalase and superoxide dismutase activity

OBJECTIVES

To study the effects of partial bladder outlet obstruction on the cell's anti-oxidant defense mechanisms, superoxide dismutase and catalase, in order to elucidate how the bladder responds to oxidative stress.

METHODS

Four groups of eight rabbits were subjected to partial bladder outlet obstruction for 4, 8 and 12 weeks. Eight sham rabbits were used as the control group. The bladders were removed under anesthesia, and the muscle and mucosa were separated, frozen and stored at -80°C for analysis. Superoxide dismutase and catalase assays were carried out on these tissues. The groups were also categorized by severity (mild, intermediate and severe) of decompensation, as well as duration.

RESULTS

When separated by duration, catalase activity of the mucosa was significantly higher in the control and the 12-weeks obstructed rabbits. This activity was lower than the control in the 4- and 8-weeks obstructed rabbits. When separated by severity, catalase activity of the mucosa was significantly higher and severely decompensated than the muscle in the controls. When separated by duration or severity, superoxide dismutase activity of the muscle was significantly lower than controls for all obstructed rabbits. The activities of both superoxide dismutase and catalase were significantly reduced in the severely decompensated bladder smooth muscle, but not in the 12-weeks obstructed bladder smooth muscle.

CONCLUSIONS

Partial bladder outlet obstruction has significant effects on the activity of both superoxide dismutase and catalase in the bladder, with variations that are dependent on the severity and duration of the obstruction.

Nitrotyrosine Density of Rabbit Urinary Bladder Muscle and Mucosa Measured via Western Blotting and 96-Well Plate Analysis

Purpose. Nitrotyrosine was quantitated in rabbit bladder muscle and mucosa using two analytical systems: Western blotting analyses and a 96-well plate quantitative analysis kit. Materials and Methods. Rabbit bladder muscle and mucosa were obtained from control rabbits. For the Western analysis, the samples were loaded into a SDS page gel and then transferred to a PVDF membrane. The optical density was measured using a Kodak Scanner. Using the 96-well plate, the samples and standards were loaded, incubated with primary and secondary antibody, washed and vacuumed with 10x wash buffer three times between each incubation period. Stop buffer was added to the plate and the results were quantified via the plate reader. Results. For both muscle and mucosa tissue, the optical density readings were linear with tissue concentration; the concentration of nitrotyrosine in the mucosa was significantly higher than in the muscle. However, whereas the Western blot analysis is based on relative optical densities, the 96-well plate kit provides a truly quantitative analysis. Discussion. Mucosa tissue displayed a higher density of nitrotyrosine than did detrusor muscle tissue. This may well be due to the significantly higher metabolic activity of the mucosa compared to the muscle.

Effect of aging on the response of biochemical markers in the rabbit subjected to short-term partial bladder obstruction

PURPOSE

Partial bladder outlet obstruction (PBOO) results in marked biochemical alterations in the bladder. In this study, we focused on comparison of thapsigargin sensitive sarco/endoplasmic reticulum Ca(2+) ATPase activity (SERCA) and Citrate Synthase after short term PBOO in young versus old rabbits.

MATERIALS AND METHODS

A total of 20 young and 20 mature male rabbits were divided into 4 sub-groups of 5 rabbits each (4 obstructed and 1 sham-control rabbit). The rabbits in the groups were evaluated after 1, 3, 7, and 14 days of obstruction, respectively. The activities of SERCA and citrate synthase were examined as markers for sarcoplasmic reticular calcium storage and release and mitochondrial function, respectively.

RESULTS

The SERCA activity of bladder body smooth muscle in the young animals increased at 7 and 14 days. For the old rabbits, the SERCA activity decreased significantly by 1 day and remained this level throughout the course of obstruction, and was significantly lower than young at all time periods. The citrate synthase activity in the young animals decreased over the 1-7 days, and then returned toward control level by 14 days following obstruction. In the old animals, citrate synthase activity of bladder body smooth muscle progressively decreased over the course of the study, and was significantly lower in the old than the young animals after 14 days obstructed.

CONCLUSION

The urinary bladders of the young rabbits have a considerable greater ability to adapt to PBOO than do those of the old rabbits. The deterioration of mitochondrial and SR function may be important mechanisms underlying geriatric voiding dysfunction.

Preventive Effects of Ginkgo biloba Extract on Ischemia-Reperfusion Injury in Rat Bladder

AIMS

The aim of this experimental study was to evaluate the effects of Ginkgo biloba (EGb 761) on ischemia-reperfusion (I-R) injury in the rat bladder.

METHODS

A bladder I-R injury was induced by abdominal aorta occlusion by ischemia for 30 min, followed by 45 min reperfusion in rats. The rats were divided into four groups of 7 rats each; the control, I-R, and I-R groups were pretreated intraperitoneally with 50 or 100 mg/kg G. biloba 60 min before ischemia induction. Contractile responses to carbachol through isolated organ bath studies were recorded, histological sections were evaluated by light microscopy, and TUNEL staining was performed for the evaluation of apoptosis.

RESULTS

In the I-R group, the contractile responses of the bladder strips were lower than those of the control group (p < 0.01-0.001) and were restored by pretreatment with 100 mg/kg G. biloba (p < 0.05-0.001). Decreased polymorphonuclear leukocyte infiltration was detected in the G. biloba pretreatment groups when compared to the I-R group during histological evaluation. The ratio of TUNEL-positive nuclei was 1.84% in the I-R group, whereas it was decreased in both of the G. biloba pretreatment groups (p < 0.01, p < 0.01).

CONCLUSION

Our data indicated that G. biloba has a preventive effect on I-R injury in rat urinary bladder.

The influence of changes in extracellular and intracellular sodium concentration on detrusor contractility

OBJECTIVE

To determine the role of Na+-Ca2+ exchange in the regulation of isolated detrusor smooth muscle contractility.

MATERIALS AND METHODS

Isolated guinea-pig detrusor strips were used to record isometric tension generated by; (a) electrical-field stimulation to elicit nerve-mediated responses; and (b) adding carbachol or superfusing with a high-K+ solution. The [Na+] gradient between extracellular and intracellular compartments was altered by: (i) reducing superfusate [Na+] in stages from 140.2 to 10.2 mm; (ii) addition of the cardiac glycoside strophanthidin (200 microm). RESULTS Reducing extracellular [Na+] reversibly reduced the magnitude of nerve-mediated contractions but increased the resting tension and magnitude of carbachol-induced contracture. The mean (sd) [Na+] required for a half-maximum effect on attenuating contractions, at 85.9 (6.2) mm, and developing contracture, at 59.1 (14.3) mm, were significantly different. The time constants of changes to nerve-mediated contractions and carbachol contracture were also significantly different, at 147 (5) vs 1207 (386) s, respectively. These differences suggest that separate mechanisms influence nerve-mediated contraction and contracture in low-Na+ solutions. Exposure to the cardiac glycoside strophanthidin produced a similar effect to low-Na+ solutions for carbachol contracture. Low-Na+ solutions had no significant effect on contractures induced by high extracellular [K+]. CONCLUSION Reducing the transmembrane [Na+] difference increases intracellular [Ca2+]. This increase is largely accommodated in intracellular stores, that can be released by exogenous carbachol. The results are consistent with the presence of a functional Na+-Ca2+ exchanger in the surface membrane. The lack of effect of low-Na+ solutions on contractures evoked by membrane depolarization is consistent with this conclusion. The reduction of the nerve-mediated contraction by low-Na+ solution might result from blockade of the nerve action potential.

The Immediate Effect of Castration on Female Rabbit Bladder Blood Flow and Tissue Oxygenation

BACKGROUND

The female urinary bladder is a target organ for estrogen. Reductions in circulating estrogen have been associated with urothelial and vaginal atrophy and bladder disorders including incontinence and increased incidence of bladder infections. We determined the effect of short-term ovariectomy on sex hormones, bladder blood flow, and tissue oxygenation in the rabbit model.

MATERIALS AND METHODS

Female New Zealand White rabbits were ovariectomized and evaluated on 1, 3, and 7 days after ovariectomy. Tissue oxygenation (pO2) and blood flow were measured with oxylab system of real time measurements. Serum estrogen and progesterone were determined at sacrifice. Tissue hypoxia was localized histologically using Hypoxyprobe-1 immunohistochemistry.

RESULTS

Short-term ovariectomy caused rapid decreases in serum estrogen and progesterone, significant decreases in urothelial oxygenation and blood flow. No significant decreases in blood flow or oxygenation were noted for the detrusor smooth muscle. Immunohistochemistry confirmed the presence of urothelial hypoxia at all times after ovariectomy. Bladder muscle did not demonstrate significant levels of hypoxia.

CONCLUSION

The bladder urothelium is extremely sensitive to short-term ovariectomy, with significant urothelial hypoxia seen by post-ovariectomy day 1. Urothelial hypoxia may play a significant role in pelvic pain syndromes, incontinence, and increased susceptibility to bladder infection.

Acute alterations in biochemistry, morphology and contractility of rat isolated urinary bladder via increased intra-abdominal pressure

OBJECTIVE

To determine the acute effects of increased intra-abdominal pressure (IAP) on the biochemistry, morphology and contractility of the rat isolated urinary bladder using an experimental laparoscopy model.

METHODS

We divided 24 adult female Sprague-Dawley rats into three groups. The control group (group I) was not subjected to increased IAP. In groups II and III, IAPs of 10 and 20 mm Hg, respectively, were established by carbon dioxide pneumoperitoneum for 60 min. Thirty minutes after desufflation, the rat urinary bladder dome was removed for in vitro pharmacological investigation, measurement of malondialdehyde (MDA) levels and histopathological examination. Statistical comparisons between groups were performed.

RESULTS

Tissue MDA levels in groups II and III were significantly higher than in the control group. In group II, only the lamina propria was significantly damaged. However, the epithelium, lamina propria, and serosa were significantly damaged in group III. Acetylcholine potentiated contractions in both IAP groups. Increased responses to electrical field stimulation in the IAP groups were significant only in group II.

CONCLUSIONS

In this experimental model, 10 and 20 mm Hg of IAP induced by pneumoperitoneum increased MDA levels and caused important changes in the morphology and contractile response of the urinary bladder.

Determination of main low molecular weight antioxidants in urinary bladder wall using HPLC with electrochemical detector

The aim of the present work was to develop validated HPLC method using electrochemical detector for simultaneous detection of low molecular weight antioxidants (LMWA) in urinary bladder. Furthermore, the method was applied to study the distribution of LMWA in urinary bladder wall. The ascorbic acid (AA), glutathione in reduced (GSH) and oxidized (GSSG) form and uric acid (UA) were resolved by isocratic elution from C18 reversed-phase column. The bladder tissue sample preparation involved extraction with meta-phosphoric acid solution for LMWA stabilization. The AA, GSH and UA tissue peak was identified by different approaches. The obtained method validation parameters were in acceptable range: intra-day precision (<4.4%), intra-day accuracy (<8.4%), inter-day precision (<9.4%) and inter-day accuracy (<15.6%). Additionally, the method provided good linearity (r2>0.99) and recoveries (98.9-112.6%). The distribution of LMWA in urinary bladder was determined by measuring their concentration in bladder wall layers: urothelium, lamina propria, muscularis and serosa. The validated method was able to quantify the reduced form of all three LMWA in all four bladder wall layers. The LMWA concentrations were decreasing from urothelium to serosa except of UA. The developed HPLC method with electrochemical detection of LMWA is simple, fast and can be used for simultaneous quantification of LMWA in tissues, which contain low concentrations of antioxidants.

Treatment of interstitial cystitis

Although the symptoms of interstitial cystitis (IC)--a debilitating, chronic disease characterized by urinary urgency and frequency, and bladder and pelvic pain on bladder filling--are easily confused with those of urinary tract infections, there is an absence of an underlying infection, and antibiotic therapy is of no therapeutic benefit. Severe cases of this disorder, which affects mainly women, can have a great negative impact on the quality of life of patients because of extreme urinary frequency. The diagnosis of IC is difficult and should be based on patient history, physical examination, and cystoscopy. A large number of pharmacologic treatments have been used to treat this condition with limited success, including pentosan polysulfate, heparin, antihistamines, tricyclic antidepressants, intravesical dimethyl sulfoxide, and bacille Calmette-Guérin. Among the potentially effective new treatment modalities currently under investigation are suplatast tosilate, resiniferatoxin, botulinum toxin, and gene therapy to modulate the pain response. As knowledge of the pathogenesis of IC increases through intensified research, the ability to provide effective treatment to patients with this disease will improve.

N(G)-nitro-L-arginine methylester, a nitric oxide synthase inhibitor, diminishes apoptosis induced by ischemia-reperfusion in the rat bladder

AIMS

To evaluated the effects of N(G)-nitro-L-arginine methylester (L-NAME), a nitric oxide synthase (NOS) inhibitor, on apoptosis induced by ischemia-reperfusion injury in the rat through a muscle bath and TUNEL staining.

METHODS

The rat abdominal aorta was clamped to induce ischemia-reperfusion (I-R) injury in the rat bladder dome with or without L-NAME (30 mg/kg, i.p. 30 minutes before the ischemia) according to our previous reports [Saito et al., 1998 Life Sci. 62:PL149-56; Saito and Miyagawa, 1999 J. Urol. 162:1490-5]. Some rats were exposed to 30 minutes of ischemia only, whereas others also received 30 minutes, 3 days, or 7 days of reperfusion after the ischemia. Muscle bath studies with carbachol and 100 mM KCl were performed to confirm the bladder function. TUNEL and hematoxylin and eosin staining were performed in the experimental rat bladders to detect apoptosis.

RESULTS

The contractile responses of the rat bladder dome after 30 minutes of ischemia differed slightly, not significantly, from those of controls. Reperfusion (30 minutes) produced significant reductions in the contractile responses to carbachol and KCl in the rat bladders. The treatment with L-NAME significantly reduced the extent of reperfusion injury, as judged by pharmacologic experiments. At 3 and 7 days after the induction of ischemia-reperfusion, the contractile responses were improved compared with the 30-minute reperfusion group. For each duration group, treatment with L-NAME significantly increased the contractile responses compared with the I-R group without L-NAME. Ischemia-reperfusion induced apoptosis, and the peak in TUNEL-positive cells was observed 3 days after the insult. Pretreatment with L-NAME reduced the induction of apoptosis.

CONCLUSION

Our data indicated treatment with L-NAME can reduce apoptosis induced by ischemia-reperfusion in the bladder.

Different distribution of nitric oxide synthase and soluble guanylyl cyclase activities in the detrusor and proximal urethra of the rabbit

PURPOSE

We investigated the different distributions of nitric oxide synthase (NOS) and soluble guanylate cyclase activities in the detrusor and proximal urethra in the rabbit.

MATERIALS AND METHODS

The detrusor and proximal urethra were excised, the mucosa and muscularis were separated and each layer was homogenized to measure the activities of NOS as well as baseline and sodium nitroprusside (SNP) activated soluble guanylate cyclase. Isometric tension experiments were performed in detrusor and urethral strips with and without mucosa.

RESULTS

In the detrusor NOS and sodium nitroprusside activated soluble guanylate cyclase activities in the mucosa were much higher than in the muscularis. While in the proximal urethra NOS activity in the 2 layers was similar, SNP activated soluble guanylate cyclase activity in the muscularis was 2.8 times higher than in the mucosa. Removing the mucosa reduced nitric oxide (NO) mediated neurogenic relaxation in the proximal urethra, while no relaxation responses could be elicited by electrical field stimulation with or without mucosa in the detrusor. On the other hand, removing the mucosa did not affect SNP or 8-bromo-cyclic guanosine monophosphate induced relaxation in the detrusor and proximal urethra.

CONCLUSIONS

In the detrusor NOS and soluble guanylate cyclase activities were mainly detected in the mucosa, while in the urethra these activities were distributed throughout the mucosa and muscularis. Also, the mucosa in the urethra but not in the detrusor contributed to electrical field stimulation induced, NO mediated relaxation. These findings confirm previous studies demonstrating that NO has a different role in the detrusor than in the proximal urethra.

The aging bladder--a significant but underestimated role in the development of lower urinary tract symptoms

There are three major areas in which bladder dysfunction causes considerable losses in quality of life: detrusor instability, impaired detrusor function and detrusor reaction on bladder outlet obstruction. Considerable changes in detrusor morphology, detrusor innervation and bladder metabolism are seen with aging and obstruction. This causes dysfunction and lower urinary tract symptoms. The relation between aging per se and external influence on the detrusor from diseases in the nervous system, in the vascular supply and in the lower urinary tract itself is poorly understood. To improve our ability to prevent and treat these conditions we need more insight in these pathophysiological conditions.

Effect of chronic bladder outlet obstruction on blood flow of the rabbit bladder

PURPOSE

Previous studies have shown that the initial reaction of the rabbit bladder to partial bladder outlet obstruction is increased blood flow at day 1 and a return to baseline blood flow at 1 week. Mucosal and muscle blood flow followed this pattern but mucosal blood flow was always 4 to 5-fold greater. In this study we examined the effect of 4 weeks of outlet obstruction on bladder blood flow and correlated it with the severity of bladder contractile dysfunction.

MATERIALS AND METHODS

A total of 14 male New Zealand White rabbits underwent partial outlet obstruction creation by standard methods. After 4 weeks the rabbits were anesthetized, and blood flow to the muscle and mucosa was determined by standard fluorescent microsphere technique. A section of each detrusor was used for in vitro contractility studies. Contractile responses to field stimulation, carbachol and potassium chloride were determined. A section of each detrusor tissue was fixed in formalin and used to determine the smooth muscle volume fraction.

RESULTS

Four weeks of partial bladder outlet obstruction caused a significant and variable increase in bladder weight and a decrease in blood flow to bladder muscle without changes in the blood flow to mucosa. There was a clear correlation between the severity of contractile dysfunction, bladder weight and the magnitude of the decrease in blood flow in muscle. The smooth muscle volume fraction remained stable at approximately 40%.

CONCLUSIONS

Bladder decompensation was associated with decreased blood flow to bladder smooth muscle. Because compensated obstructed bladders with relatively normal contractile function are also hypertrophied but have normal blood flow, decreased blood flow in decompensated bladders is not simply a response to bladder hypertrophy. From this study we hypothesize that decreased blood flow to bladder smooth muscle is an etiological factor in bladder contractile dysfunction (bladder decompensation) secondary to partial outlet obstruction.

Identification of components of Prunus africana extract that inhibit lipid peroxidation

Extractive and chromatographic separations were performed on V-1326, a chloroform extract from the bark of Prunus africana (also referred to as Pygeum africanum), which is used to treat the symptoms associated with benign prostate hyperplasia (BPH). The relative amounts of eleven identified constituents in crude V-1326 and in separated fractions were determined using gas chromatographic analysis. The ability of V-1326 and its separated fractions to inhibit ferrous ion-induced stimulation of lipid peroxidation in microsomal preparations from rabbit livers was evaluated. The extract, V-1326, and fractions containing high levels of myristic acid potently inhibited lipid peroxidation.

Bladder mucosal cell abnormalities and symptomatic outcome after transurethral resection of the prostate

OBJECTIVES

To identify predictors of poor symptomatic improvement after transurethral resection of the prostate (TURP), we investigated mucosal cell abnormalities in men about to undergo this procedure, and any association between these abnormalities and pre- and postoperative urinary tract symptoms.

METHODS

Bladder lavages were obtained from patients undergoing TURP for outflow obstruction during 1995 to 1996 at the Repatriation General Hospital. Pressure flow studies were obtained preoperatively, and International Prostate Symptom Scores and flow rates were obtained preoperatively and 3 months and 2 years postoperatively. Cells from bladder washings were examined flow-cytometrically for Tn antigen expression and DNA cell cycle parameters.

RESULTS

Of 192 patients recruited, 145 met the inclusion criteria. The frequency of Tn antigen expression, aneuploidy, and tetraploid aneuploidy in bladder mucosal cell washings in this group was comparable to a previous study. Weak, statistically significant associations were found between S-phase fraction and the initial International Prostate Symptom Score irrespective of whether total S-phase fraction cell numbers or categories were used. The trend of each of these associations was consistent (ie, patients with higher S-phase fraction values had more severe symptoms, poorer quality of life, and lower flow rates). The association was maintained at 3 months postoperatively but not at 2 years. Potential confounding factors did not explain the association.

CONCLUSIONS

Bladder mucosal cell abnormalities can be found in men selected to undergo TURP to relieve obstruction and are associated with poor short-term symptomatic outcome. Further studies are needed to confirm these findings, in particular any association between higher mucosal cell proliferation rates and the presence of lower urinary tract symptoms.

Fatty acid profiles in normal and obstructed rabbit bladder smooth muscle and mucosa

Partial bladder outlet obstruction results in progressive loss in contractile and specific cellular and subcellular membrane functions. There is evidence that ischemic activation of proteolytic and lipolytic enzymes play a major role in the etiology of bladder dysfunction secondary to partial outlet obstruction. The specific aims of the current study were to determine the fatty acid profiles in normal rabbit bladder smooth muscle and mucosa and to determine the effect of partial outlet obstruction on the distribution and content of free and total fatty acids. Fatty acids were isolated by extraction from obstructed and normal bladder smooth muscle and mucosal homogenates, and samples were analyzed by gas chromatography. All samples contained palmitic, stearic, oleic, linoleic, and arachidonic acids. A 100% increase in total fatty acid concentration was observed in the obstructed bladder muscle tissue relative to normal bladders, although the concentration of total arachidonic acid remained constant in the two groups. Significantly higher levels of free arachidonic acid were observed in the obstructed bladder muscle group compared to the normal group. No changes were observed in fatty acid concentrations or distributions in bladder mucosa. These data show that fatty acid composition is altered as a result of bladder obstruction and support the idea that obstruction increases the activity of lipase activity and/or decreases acyl transferase activity. Neurourol. Urodynam. 18:697-711, 1999.

Rabbit versus rat urinary bladder: effects of in vitro hypoxia

PURPOSE

Studies indicate that bladder hypoxia may be an etiological factor for lower urinary tract dysfunction. Rat and rabbit are two species of experimental animals used frequently to study lower urinary tract function and dysfunction. The objective of this study was to compare directly effects of in vitro hypoxia on contractile responses of rat and rabbit urinary bladder to different forms of stimulation.

METHODS

Sexually mature male New Zealand White rabbits and Sprague-Dawley rats were compared. Each bladder was excised while the animal was anesthetized, and longitudinal bladder strips were cut, then mounted in organ baths. A tension of 2 g was placed on all strips. Effects of 1, 2, 3 and 4 h hypoxia followed by 1 h of reoxygenation on contractile responses of bladder strips to field stimulation (FS), carbachol (100 micromol/l), ATP (1 mmol/l) and KCl (120 mmol/l) were determined.

RESULTS

Contractility, per unit tissue mass, of rat bladder strips was significantly greater than that of rabbit bladder strips in response to FS (all frequencies), carbachol, KCl and ATP. Hypoxia (followed by reoxygenation) resulted in time-dependent progressive reduction in contractile responses of bladder strips to all stimuli. Rat bladder was significantly more sensitive to hypoxia than rabbit bladder in response to FS and carbachol. Hypoxia induced similar effects on rat and rabbit bladder responses to ATP and KCl.

CONCLUSION

Rat bladder neurogenic and cholinergic responses are significantly more sensitive to hypoxia than are those of rabbit bladder, which may be due to the rat bladder's greater contractile force generation and previously reported higher Ca2+-ATPase activity.

Subcellular Distribution of Free Fatty Acids, Phospholipids, and Endogenous Lipase Activity of Rabbit Urinary Bladder Smooth Muscle and Mucosa

OBJECTIVES

The urinary bladder wall can be separated into two major compartments: the urothelium (mucosa) and the detrusor smooth muscle. Specific dysfunctions of both layers have been linked to ischemia, which may induce significant cellular and subcellular membrane damage via the activation of selective calcium dependent and independent hydrolytic enzymes. Preliminary to investigating changes in cell membrane composition induced by ischemia, we measured the free fatty acid (FFA) and phospholipid (PL) content of normal rabbit bladder muscle and mucosal cellular and subcellular membranes, and characterized the endogenous lipase activity.

METHODS

Rabbit bladders were excised and the muscle and mucosal layers separated; each layer was homogenized, then fractionated by differential centrifugation. Endogenous lipase activity of the homogenates, and FFA and PL concentrations of the homogenates and subcellular fractions were measured.

RESULTS

(1) The basal FFA concentration of the mucosal homogenates was 5 times that of the muscle homogenates. (2) The basal PL concentrations of the two tissues were similar. (3) Subcellular studies: FFA concentration was greatest in the mitochondrial fraction of both compartments. In the mucosa, PL concentration was significantly greater in the mitochondria and microsomes than in the other fractions; in the smooth muscle, the PL concentration was highest in the mitochondria. (4) The maximal endogenous lipase activity was 10 times higher in the mucosal homogenates than in the muscle homogenates.

CONCLUSIONS

These results are consistent with those of previous studies which indicate that the mucosa is metabolically more active than the resting smooth muscle, which may cause the mucosa to be significantly more sensitive than the muscle to hypoxic/ischemic damage.

Potential role of rel/nuclear factor-kappaB in the pathogenesis of interstitial cystitis

PURPOSE

Despite assertive investigation in the last 2 decades, interstitial cystitis remains an unresolved problem in clinical urology, and its etiology and the mechanisms involved in its pathogenesis are still a matter of conjecture. Recently nuclear factor (NF)-KB has been implicated in chronic inflammatory diseases, and is thought to be a key regulator of genes involved in response to infection, inflammation and stress. We document the presence, pattern and distribution of NF-kappaB in bladder biopsies from patients with interstitial cystitis.

MATERIALS AND METHODS

Bladder biopsies from 7 women clinically diagnosed with interstitial cystitis according to National Institute for Diabetes and Digestive and Kidney Diseases criteria and 5 women diagnosed with urinary incontinence were used for immunohistochemical localization of p65, an NF-kappaB subunit.

RESULTS

Our immunohistochemical localization experiments indicate that NF-kappaB was predominantly activated in bladder urothelial cells and cells of the submucosal layer in biopsies from patients with interstitial cystitis compared to controls. While activation was evident by intense nuclear localization of NF-kappaB in all interstitial cystitis specimens, diffuse and faint immunostaining was observed in control samples. The results also indicate that activation of NF-kappaB correlated with disease occurrence.

CONCLUSIONS

The fact that NF-kappaB is capable of transactivating pro-inflammatory mediators, which in turn can amplify NF-kappaB activation by a positive regulatory loop, suggests that inflammatory and/or immune responses in interstitial cystitis can be exacerbated possibly by persistent activation of this nuclear factor. We believe that our study provides a novel basis for investigating the role of NF-kappaB activation in the pathophysiology of interstitial cystitis and further opens a frontier for the development of an innovative therapeutic approach to interstitial cystitis.

Effect of ischemia-reperfusion on contractile function of rat urinary bladder: possible role of nitric oxide

Because there are increasing evidences that nitric oxide (NO) plays important roles in ischemia-reperfusion injury in several systems, we investigated the role of NO in ischemia-reperfusion injury of the rat urinary bladder. Rat abdominal aorta was clamped with a small clip to induce ischemia-reperfusion injury in the rat bladder dome. In functional studies, contractile responses to carbachol were cumulatively measured after the urinary bladder was treated with various duration (0, 30, 60, and 90 min) of ischemia. The injury of rat bladder functioning was dependent on ischemic periods. Significant decreases in the Emax (maximum contractile response) values were observed in the bladder subjected to 60 or 90 min ischemia. Furthermore, the subsequent 30 min reperfusion caused additional damages of the contractile response in bladder muscles. To investigate the role of NO in the ischemia (30 min)-reperfusion (30 min) injury, NG-nitro-L-arginine methylester (L-NAME) was injected intraperitoneally 30 min before the ischemia. Treatment of L-NAME (30 and 100 mg/kg) partly but significantly prevented the reduction contractile responses to carbachol of the rat bladder dome. In histological studies, the ischemia-reperfusion caused infiltration of leukocytes and rupture of microcirculation in the regions of submucosa and smooth muscle without a corresponding sloughing of mucosal cells. The histological damages were also prevented by treatment with L-NAME. Therefore, these data suggested that ischemia-reperfusion of the urinary bladder may result in dysfunction of the contractile response to autonomic nervous system and that nitric oxide may act as a cell/tissue damaging agent in ischemia-reperfusion injury.

Effect of ischemia of the rabbit bladder on Ca-Mg-activated ATP-ase activity

This investigation is concerned with the effect of ischemia on the activity of Ca-Mg-stimulated ATP-ase in rabbit bladder tissue. White New Zealand male rabbits were used for the experiments. Ischemia was produced by clamping of the vesical arteries. After 1 and 2 hours the clamps were removed, and the animals were sacrificed 2 days later. The bladders were removed, and the muscle and mucosal parts of the bladders were separated. In some experiments with 2-hour ischemia the animals were allowed to recover for 7 days. Homogenates were made of the muscle and mucosal tissue and separated by differential centrifugation into three parts: 1) an initial particulate fraction obtained by low-speed centrifugation; 2) a supernate fraction free of mitochondria; and 3) a mitochondrial-rich fraction. ATP-ase activity was determined in the different fractions in the presence of magnesium or calcium as the activating ion, and the results were expressed as nmols/mg protein/minute. The following results were obtained: with the supernates, ischemia was found to produce a marked inhibition of enzyme activity that was large and significant in muscle tissue after 1 hour and in mucosal tissue after 2 hours. Seven days after termination of 1 hour of ischemia, the ATP-ase activity of the muscle fraction had been partially restored towards normal. Activity of ATP-ase when measured in the particulate fraction was less sensitive to the effect of ischemia; a significant diminution of enzyme activity in preparations from muscle was seen only after 2 hours of ischemia, and no inhibition was observed with mucosal tissue. ATP-ase of muscle mitochondria was severely inhibited by ischemia, and the effect of 1 hour of ischemia was not reversed 7 days after the insult. Mitochondria from mucosal tissue were affected to only a small extent by ischemia. In all cases, results were similar whether magnesium or calcium was used for activation of the enzyme.