Effects of partial outlet obstruction of the rat urinary bladder on micturition characteristics, DNA synthesis and the contractile response to field stimulation and pharmacological agents

Decreased Angiopoietin Expression in Underactive Bladder Induced by Long-term Bladder Outlet Obstruction

PURPOSE

Ischemia of the bladder can occur if neovascular formation cannot keep pace with hypoxia induced by chronic bladder outlet obstruction (BOO). The aim of this study was to examine changes in angiogenesis growth factor expression generated by chronic BOO in a rat model of underactive bladder.

METHODS

Twenty female Sprague-Dawley rats aged 6 weeks were assigned to 4 groups (5 rats per group). Group 1 was the control. Group 2 underwent sham surgery. The rats in groups 3 and 4 underwent BOO and were followed up for 1 week and 8 weeks. Cystometry was carried out together with bladder tissue analysis at 1 week and 8 weeks postoperatively. Real-time polymerase chain reaction (PCR) assays were conducted to determine the expression level of angiogenesis-related growth factors. A hypoxia signaling pathway PCR array was additionally carried out.

RESULTS

The group that underwent BOO for 8 weeks showed abnormal bladder function, with a diminished intercontraction interval, decreased maximal voiding pressure, and higher volume of residual urine (P<0.05). Hypoxia-inducible factor-1 alpha expression was elevated in this group. The expression levels of vascular endothelial growth factor (VEGF) and VEGF receptor messenger RNA (mRNA) in the BOO group were comparable to those in the control group. However, angiotensin/tie receptor mRNA expression levels increased at 1 week after BOO, but decreased at 8 weeks after BOO. In animals that underwent BOO, fewer blood vessels exhibited positive immunofluorescent staining for von Willebrand factor. Alterations were also seen in the hypoxia signaling pathway PCR array.

CONCLUSION

In a rat model of underactive bladder caused by surgical BOO, reduced angiopoietin expression was demonstrated. This observation might underlie visceral ischemia and fibrosis associated with the procedure. The findings of this study might offer an improved understanding of the disease processes underlying BOO and facilitate selection of the appropriate time to repair the organ in this condition.

Changes of proapoptotic and antiapoptotic genes affect sensitivity to apoptotic stimuli in impaired contractility due to long term bladder outlet obstruction

INTRODUCTION

The normal biological process that necessitates cell removal greatly depends on apoptosis. Long term bladder outlet obstruction (BOO) causes damaged smooth muscle cells to undergo apoptosis. However, smooth muscle cell apoptosis that BOO causes is not well known in impaired bladder contractility. Therefore, we designed this study to investigate whether long-term BOO could induce apoptosis activities and to obtain an expression profile of apoptosis related genes.

MATERIALS AND METHODS

We used 10 Sprague-Dawley six-week-old female rats. We separated them equally into two groups: a sham intervention group (group 1) and an eight-week BOO group (group 2). We conducted cystometric evaluation eight weeks following BOO onset, with processing of bladder tissue for PCR array. Every array comprised 84 genes, which were established to contribute to an apoptosis response, cell differentiation and metabolism, and 12 sequences were established for the regulation of loading and the quality of cDNA. We performed real-time PCR. Changes in gene expression presented as a fold increase/decrease. Alterations of more than two-fold constituted the cut-off determining expression.

RESULTS

Group 2 had a greater bladder weight and Impaired bladder contractility. Immunofluorescent staining with CAS3, TUNEL showed increased in the BOO group. In comparison to group 1, group 2 exhibited an at least two-fold upregulation in five genes, the Bcl-2 (15.1), Birc5 (5.8), Cd40lg (7.5), Il10 (16.2), and Naip2 (13.2). They also demonstrated at least a two-fold downregulation in the PRLR (-18.1) gene. Genes Bcl2ald, Circ5, Cd40lg, Il10, Naip2, and PRLR were among the genes with activity against apoptosis. TNF, STAT3 and TP53 mediated the effect that genes had on one another.

CONCLUSION

This study demonstrated that the relative ratios of pro- and antiapoptotic genes determine bladder cell sensitivity cells to apoptotic stimuli in impaired contractility caused by long term BOO. Although we cannot confirm whether this finding is the result of the decompensated phase of the bladder or the process, the gene expression profiles could explain molecular mechanisms of apoptosis in impaired bladder contractility caused by long-term BOO with further studies.

Enhanced Hypoxia-Associated Genes in Impaired Contractility From Bladder Outlet Obstruction

BACKGROUND

Hypoxia damages the bladder wall and contributes to the initiation of bladder dysfunction. The change of hypoxia is not well known in impaired bladder contractility caused by long-term bladder outlet obstruction (BOO). We aimed to find out whether hypoxia of bladder tissue is present and what signaling mechanisms are involved in the decompensated bladder in BOO.

METHODS

Twenty 6-week-old female Sprague-Dawley rats were divided into 2 groups, 10 rats each: group 1, sham operation; group 2, BOO for 8 weeks. Eight weeks after the onset of BOO, we did cystometric evaluation and processed polymerase chain reaction (PCR) array for hypoxia pathway using bladder tissues. The PCR array consists of 84 genes known to be involved in the hypoxic response, cell differentiation, and metabolism. We did quantitative PCR (qPCR) and immunohistochemical staining of bladder tissue for hypoxia.

RESULTS

Eight genes were at least 2-fold upregulated and 3 genes were at least 2-fold downregulated in BOO group, compared with the sham operation group. The up-regulated genes (fold change) belonging to the hypoxia-inducible factor (HIF) 1 interactor included Cdkn2a (11.0), and the down-regulated genes belonging to HIF and co-transcription factors included Hif3a (-39.6) and Per1 (-5.1) by BOO. Genes influenced each other by means of TGFβ1, TNF, and TP53.

CONCLUSION

Hypoxia genes were increased in impaired contractility because of long-term BOO. The gene expression profiles could explain the molecular mechanisms of hypoxia in impaired contractility because of long-term BOO.

Improved bladder contractility after transplantation of human mesenchymal stem cells overexpressing hepatocyte growth factor into underactive bladder from bladder outlet obstruction models of rats

Introduction

An underactive bladder can lead to difficulty in voiding that causes incomplete emptying of the bladder, suggesting the need for a new strategy to increase bladder contractility in such patients. This study was performed to investigate whether human mesenchymal stem cells (hMSCs) were capable of restoring bladder contractility in rats with underactive bladder due to bladder outlet obstruction (BOO) and enhancing their effects by overexpressing hepatocyte growth factor (HGF) in hMSCs.

Materials and methods

The hMSCs were transplanted into the bladder wall of rats. Fifty female Sprague-Dawley rats at six weeks of age were divided into five groups: group 1: control; group 2: sham intervention; group 3: eight-week BOO; group 4: BOO rats transplanted with hMSCs; and group 5: BOO rats transplanted with hMSCs overexpressing HGF. Two weeks after the onset of BOO in groups 4 and 5, hMSCs were injected into the bladder wall. Cystometry evaluation was followed by Masson’s trichrome staining of bladder tissues. Realtime PCR and immunohistochemical staining were performed to determine for hypoxia, apoptosis, and angiogenesis.

Results

Collagen deposition of bladder increased in BOO but decreased after transplantation of hMSCs. The increased inter-contraction interval and residual urine volume after BOO was reversed after hMSCs transplantation. The decreased maximal voiding pressure after BOO was restored by hMSCs treatment. The mRNA expression of bladder collagen1 and TGF-β1 increased in BOO but decreased after hMSCs transplantation. The decrease in vWF-positive cells in the bladder following BOO was increased after hMSCs transplantation. Caspase 3 and TUNEL-positive apoptosis of bladder cells increased in BOO but decreased after transplantation of hMSCs. These effects were enhanced by overexpressing HGF in hMSCs.

Conclusion

Transplantation of hMSCs into bladder wall increased the number of micro-vessels, decreased collagen deposition and apoptosis of detrusor muscle, and improved bladder underactivity. The effects were enhanced by overexpressing HGF in hMSCs. Our findings suggest that the restoration of underactive bladder using hMSCs may be used to rectify micturition disorders in patients following resolution of BOO. Further studies are needed before hMSCs can be used in clinical applications.

Characteristics of the mechanosensitive bladder afferent activities in relation with microcontractions in male rats with bladder outlet obstruction

We investigated the characteristics of bladder mechanosensitive single-unit afferent activities (SAAs) in rats with a bladder outlet obstruction (BOO) and their relationship with bladder microcontractions. Male Wistar rats were divided into Sham and BOO groups. Four or 10 days after the surgery, rats were anesthetized with urethane. The SAAs of Aδ- or C-fibers from the L6 dorsal roots were recorded during bladder filling. The BOO group showed a higher number of microcontractions and lower SAAs of Aδ-fibers compared with those of the Sham group. These findings were significant at day 10 post-operatively. In contrast, SAAs of C-fibers were not significantly different between the groups at either day 4 or 10. In the BOO group at day 10, the SAAs of both Aδ- and C-fibers at the “ascending” phase of microcontractions were significantly higher than those at the other phases (descending or stationary), and a similar tendency was also observed at day 4. Taken together, during bladder filling, the bladder mechanosensitive SAAs of Aδ-fibers were attenuated, but SAAs of both Aδ- and C-fibers were intermittently enhanced by propagation of microcontractions.

The inflammatory cytokine IL-1β is involved in bladder remodeling after bladder outlet obstruction in mice

AIMS

We investigated the relationship between IL-1β and morphological and functional changes following partial bladder outlet obstruction (pBOO).

METHODS

Female wild-type C57/BL6 mice (WT) and IL-1β-/- mice (KO) were used. Animals were sacrificed either 1 or 3 weeks after pBOO or sham surgery, and their bladders were harvested to determine bladder weight, for RT-PCR to measure interleukin-1β (IL-1β), insulin growth factor-1 (IGF-1), and transforming growth factor-β (TGF-β) levels, and for histological analysis with Hematoxylin-Eosin (HE) staining. Cystometry was performed on conscious animals 3 weeks after surgery to evaluate urodynamic parameters. IGF-1 was also administered intraperitoneally to KO with pBOO, and bladder weight was then investigated.

RESULTS

IL-1β-mRNA levels were significantly higher in WT-pBOO than in WT-sham. IGF-1-mRNA and TGF-β-mRNA levels were also significantly higher in WT-pBOO than in WT-sham; however, these increases were smaller in KO-pBOO than in WT-pBOO. Bladder weight was significantly higher in WT-pBOO than in WT-sham, while increases in bladder weight were significantly suppressed in KO-pBOO. HE staining revealed the thickened bladder wall in WT-pBOO, and this phenomenon was less in KO-pBOO than in WT-pBOO. Regarding the urodynamic parameters examined, micturition pressure and bladder capacity were significantly higher in WT-pBOO than in WT-sham, but remained unchanged in KO-pBOO. The administration of IGF-1 to KO-pBOO led to similar increases in bladder weight and the thickened bladder wall as those observed in WT-pBOO.

CONCLUSION

IL-1β has the potential to induce bladder remodeling and deteriorate urodynamic parameters in pBOO.

Stromal Cell-Derived Factor 1α Induces Accumulation of Intraveneously Administered Marrow-Derived Stromal Cells in the Partially Obstructed Rat Bladder

OBJECTIVES

We investigated the time course of the stromal cell-derived factor 1α (SDF1α) expression and behavior of intravenously administered bone marrow-derived stromal (BMS) cells in the urinary bladder of partial bladder outlet obstruction (PBOO) rats.

METHODS

Study 1: Recombinant SDF1α or saline was directly injected into the bladder wall of female rats followed by intravenous administration of BMS cells isolated from green fluorescent protein (GFP) transgenic rats. The bladder was examined with immunohistochemistry to determine whether SDF1α would enhance migration of BMS cells to the bladder. Study 2: Following surgery of PBOO or sham in female rats, bladders were removed on days 1-14, and expression of hypoxia inducible factor 1α (HIF1α) and SDF1α were examined with real-time polymerase chain reaction (PCR) to determine if PBOO preferentially increased their expression. Study 3: Female rats underwent PBOO or sham surgery followed by intravenous administration of GFP-positive BMS cells. Bladders were examined with immunohistochemistry on days 1-14 to determine whether BMS cells preferentially accumulated in the bladder.

RESULTS

BMS cells were accumulated in the injection site of SDF1α but not saline in the bladder. SDF1α and HIF1α increased at day 1 after PBOO compared to sham. More BMS cells accumulated in the bladder of PBOO on day 1, and some BMS cells expressed smooth muscle phenotypes by day 14.

CONCLUSION

SDF1α induced with ischemia/hypoxia due to PBOO is implicated in the accumulation of BMS cells in the bladder and regeneration of the bladder for PBOO.

Modulation of alpha 1 adrenergic receptors on urinary bladder in rat spinal cord injury model

Purpose

Whereas many studies have focused on the vesical changes of the α1 adrenergic receptor (AR) subtypes in partial outlet obstruction, few studies have addressed the modulation of the α1 AR subtypes after spinal cord injury (SCI). Therefore, we studied the modulation of the α1 ARs in urinary bladder in a rat SCI model.

Methods

Four weeks after a SCI, the whole vesical bodies from eight female Sprague-Dawley rats and from eight controls were harvested. The total RNA was extracted from the samples and was used to prepare cDNA. We developed standard plasmid constructs of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and three α1 ARs (α1a, α1b, and α1d) to convert the cycle threshold (Ct) values from real-time polymerase chain reaction (RT-PCR) into subtype mRNA concentrations. The detected Ct values of 16 samples from RT-PCR were interpolated into the standard plasmid curves.

Results

All serially diluted standard samples showed very good linearity. The mRNA expression of GAPDH was higher in the SCI group, whereas the mRNA expression of all α1 ARs was lower in the SCI group than in the control animals. The α1a, α1b, and α1d mRNA expression in the controls was 81.7%, 3.3%, and 15.1%, respectively, whereas the α1a, α1b, and α1d mRNA expression in the SCI group was 33.5%, 5.2%, and 60.9%, respectively.

Conclusions

SCI moderates the α1 AR mRNA subtypes in the urinary bladder. The relatively increased α1d or decreased α1a AR mRNA expression may be a therapeutic candidate for controlling the symptoms of neurogenic bladder after SCI.

Species differences in the pharmacokinetics of KW-7158 [(2S)-(+)-3,3,3-Trifluoro-2-hydroxy-2-methyl-N-(5,5,10-trioxo-4,10-dihydrothieno[3,2-c][1]benzothiepin-9-yl)propanamide]: formation of hydrolyzed metabolite in human and animals

Species differences in the pharmacokinetics of KW-7158 [(2S)-(+)-3,3,3-Trifluoro-2-hydroxy-2-methyl-N-(5,5,10-trioxo-4,10-dihydrothieno[3,2-c][1]benzothiepin-9-yl)propanamide] were studied in in vivo and in vitro experiments. The exposure ratio of hydrolyzed metabolite (M2, primary metabolite in human plasma)/KW-7158 was higher than the ratio of thiophen-to-furan converted metabolite (M1)/KW-7158 in human subjects after oral administration, but the mouse, rat and dog studies gave opposite results. M2 was produced in the highest amount by the 9000g supernatant of small intestine, followed by that of liver and kidney in human subjects. After correction for protein contents, the results obtained suggested that the small intestine plays a major role in the metabolism to M2 for the first pass effect after oral administration of KW-7158. The formation of M2 was independent of the presence of NADPH and was inhibited by various esterase inhibitors. These observations suggested that the predominant enzymes or isozymes involved in the formation of M2 are esterases, which differ between humans and animals. Such differences may be one of the reasons for the species differences in the pharmacokinetics of KW-7158 between humans and animals.

Adjustable passive stiffness in mouse bladder: regulated by Rho kinase and elevated following partial bladder outlet obstruction

Detrusor smooth muscle (DSM) contributes to bladder wall tension during filling, and bladder wall deformation affects the signaling system that leads to urgency. The length-passive tension (L-T(p)) relationship in rabbit DSM can adapt with length changes over time and exhibits adjustable passive stiffness (APS) characterized by a L-T(p) curve that is a function of both activation and strain history. Muscle activation with KCl, carbachol (CCh), or prostaglandin E(2) at short muscle lengths can increase APS that is revealed by elevated pseudo-steady-state T(p) at longer lengths compared with prior T(p) measurements at those lengths, and APS generation is inhibited by the Rho Kinase (ROCK) inhibitor H-1152. In the current study, mouse bladder strips exhibited both KCl- and CCh-induced APS. Whole mouse bladders demonstrated APS which was measured as an increase in pressure during passive filling in calcium-free solution following CCh precontraction compared with pressure during filling without precontraction. In addition, CCh-induced APS in whole mouse bladder was inhibited by H-1152, indicating that ROCK activity may regulate bladder compliance during filling. Furthermore, APS in whole mouse bladder was elevated 2 wk after partial bladder outlet obstruction, suggesting that APS may be relevant in diseases affecting bladder mechanics. The presence of APS in mouse bladder will permit future studies of APS regulatory pathways and potential alterations of APS in disease models using knockout transgenetic mice.

Relaxant and contractile responses of detrusor muscle strips obtained from bladder outlet-obstructed rats treated with doxazosin enantiomers

(-)Doxazosin, one of (±)doxazosin enantiomers, was speculated to have a pharmacological enantioselectivity between the cardiovascular system and the urinary system by comparison with (+)doxazosin. Therefore, to evaluate the potential benefits of (-)doxazosin in the treatment of benign prostate hyperplasia, we compared the effects of the 3 agents, using rat mesenteric artery preparations and obstructed bladder strips. Concentration-response curves for carbachol (contractile response) and isoprenaline (relaxant response) in detrusor muscle strips of the bladder outlet obstruction (BOO) rats were shifted to the left, with significant increases in the Emax values, and significant decreases in the EC50 values by comparison with the sham-operated rats (P < 0.05, n = 10). The enhanced responses in detrusor muscle strips of the BOO rats treated with (±)doxazosin and its enantiomers at 3 mg·(kg body mass)(-1)·day(-1) for 2 weeks returned to normal levels, and the 3 agents inhibited the enhanced responses to carbachol and isoprenaline to the same extent. On the other hand, the 3 agents uncompetitively inhibited the vasoconstrictive response curves for NA in the rat isolated mesenteric artery, and the pKB value of (-)doxazosin at vascular α1-adrenoceptors was significantly smaller (P < 0.05, n = 6) than that of (+)doxazosin or (±)doxazosin. In conclusion, although (-)doxazosin inhibits vascular functional α1-adrenoceptors more weakly than (+)doxazosin, both agents equally ameliorate the enhanced responses in detrusor muscle of BOO rats, suggesting that the chiral carbon atom in the molecular structure of doxazosin does not affect its beneficial effects in the bladder smooth muscle of BOO rats.

Bladder mechanoreceptor changes after artificial bladder outlet obstruction in the anesthetized rat

AIMS

Experimental animal models of bladder outlet obstruction (BOO) have reproduced several features of BOO in man, i.e., detrusor hypertrophy, instability, frequency, and residual urine. This study was focused on the mechanisms underlying the development of residual urine in patient with benign prostatic hyperplasia (BPH) by examining changes in tension sensitivity of bladder mechanoreceptors in rat model.

METHODS

Female adult Sprague-Dawley rats including 12 BOO and 17 sham operated rats were used in this study. Cystometrograms together with the bladder afferent activity were recorded. Tension sensitivity of the afferents was determined by plotting the normalized afferent response against the contraction evoked bladder pressure at different volumes. Degree of obstruction was assessed by the wet weight of the bladder at the end of the experiment.

RESULTS

The bladder weight, maximal bladder capacity, micturition threshold volume, peak contraction force, and volume at peak contraction force were all significantly increased in obstructed animals. The threshold volume for afferent activation was increased (mean 0.60 ml compared to 0.15 ml in controls; P < 0.001), positively correlated with the bladder weight (r = 0.74). The tension sensitivity of the bladder mechanoreceptors and the slope of their normalized pressure-response functions were significantly lower at the comparable volumes in the obstructed animals.

CONCLUSIONS

Rats with BOO had bladder mechanoreceptors with higher threshold volumes and lower tension sensitivity. Such changes would result in a weaker afferent drive of the micturition reflex. Similar changes may contribute to the development of residual urine and retention in patients with BOO.

Regulation of connexin 43 by basic fibroblast growth factor in the bladder: transcriptional and behavioral implications

PURPOSE

Basic fibroblast growth factor is a candidate causative factor of detrusor overactivity in bladder outlet obstruction cases through up-regulation of the gap junction protein connexin 43. We addressed the transcriptional and behavioral implications of this axis.

MATERIALS AND METHODS

Cx43 and Cx45 mRNA expression was assessed by real-time reverse transcriptase-polymerase chain reaction in the bladder of a rat bladder outlet obstruction model and in cultured rat bladder smooth muscle cells with and without basic fibroblast growth factor treatment. Involvement of the extracellular signal regulated kinase 1/2-activator protein-1 pathway was evaluated by immunofluorescence study and a promoter-reporter assay in bladder smooth muscle cells. The effect of basic fibroblast growth factor on micturition behavior was measured in unrestrained rats under a 12-hour light/dark cycle using a controlled release system from gelatin hydrogels fixed on the bladder. The expression of extracellular signal regulated kinase 1/2 and connexin 43 protein was assessed by Western blotting of rat bladder protein.

RESULTS

Cx43 but not Cx45 mRNA expression was increased in the bladder of the obstruction model and in bladder smooth muscle cells treated with basic fibroblast growth factor. The mitogen-activated and extracellular signal-regulated kinase kinase inhibitor PD98059 blocked the stimulatory effect of basic fibroblast growth factor on connexin 43 protein expression and promoter activity, which was also decreased by mutation or deletion of an activator protein-1 cis-element of the connexin 43 promoter. In vivo application of basic fibroblast growth factor on the bladder increased urinary frequency during the latter half of the dark phase, ie the late active phase of rats (F = 5.1, 2-way ANOVA p <0.05). The expression of phospho-extracellular signal regulated kinase 1/2 and connexin 43 protein was increased in the bladder.

CONCLUSIONS

The extracellular signal regulated kinase 1/2-activator protein-1-connexin 43 axis could be a potential therapeutic target for increased urinary frequency.

The bladder-brain connection: putative role of corticotropin-releasing factor

The coordination of pelvic visceral activity with appropriate elimination behaviors is a complex task that requires reciprocal communication between the brain and pelvic organs. Barrington's nucleus, located in the pons, is central to a circuit involved in this function. Barrington's nucleus neurons project to both pelvic visceral motorneurons and cerebral norepinephrine neurons that modulate behavior. This circuit coordinates the descending limb of the micturition reflex with a central limb that initiates arousal and shifts the focus of attention to facilitate elimination behavior. The same circuitry that links the bladder and brain enables pathological processes in one target of the circuit to be expressed in the other. Urological disorders can, therefore, have cognitive and behavioral consequences by affecting components of this circuit; and in the opposing direction, psychosocial stressors can produce voiding dysfunctions and bladder pathology. The stress-related neuropeptide, corticotropin-releasing factor, which is prominent in Barrington's nucleus neurons, is a potential mediator of these effects.

The effect of bladder outlet obstruction on alpha1- and beta-adrenoceptor expression and function

AIMS

To explore possible changes in expression and/or function of alpha(1)- and beta-adrenoceptor subtypes as a cause for bladder dysfunction in a rat model of bladder outlet obstruction (BOO).

METHODS

BOO was induced in rats by partial urethral ligature. Contraction and relaxation experiments were performed with isolated bladder strips from BOO, sham-operated and non-operated (control) rats 7 days after BOO induction. mRNA expression of alpha(1)- and beta-adrenoceptor subtypes was assessed by quantitative real-time PCR.

RESULTS

Receptor-independent contraction or relaxation did not differ between BOO and sham rats. The alpha(1)-agonists methoxamine and A-61,603 caused only weak contraction without major differences between groups. Against KCl-induced tone, the beta-adrenoceptor agonists noradrenaline and isoprenaline caused similar relaxation in BOO and sham rats, whereas relaxation in response to the beta(3)-selective BRL 37,344 was attenuated. Against passive tension, noradrenaline induced relaxation in sham and control rats; in contrast, noradrenaline induced contraction at low concentrations and relaxation at high concentrations in BOO rats. The contraction component was abolished by the alpha(1)-antagonist prazosin. The mRNA expression of alpha(1D)-adrenoceptors was increased in BOO, whereas none of the other receptor mRNAs were up-regulated.

CONCLUSIONS

In a rat BOO model, weak contraction responses to alpha(1)-agonists and relaxation responses to beta-agonists are not altered to a major extent. Nevertheless, relaxation responses to the endogenous agonist noradrenaline are turned into alpha(1)-adrenoceptor-mediated contraction responses in BOO, possibly due to an up-regulation of alpha(1D)-adrenoceptors.

Suppression of bladder oxidative stress and inflammation by a phytotherapeutic agent in a rat model of partial bladder outlet obstruction

PURPOSE

Ischemia/reperfusion injury is a major etiological factor in the progression of bladder dysfunction after partial bladder outlet obstruction and it is partly mediated by the generation of free radicals. The phytotherapeutic agent Eviprostat, a popular treatment for benign prostatic hyperplasia in Japan and Germany, has antioxidant and anti-inflammatory activity. We investigated the effect of Eviprostat on oxidative stress and inflammation in bladder dysfunction in a bladder outlet obstruction rat model.

MATERIALS AND METHODS

Bladder outlet obstruction was surgically induced in male rats by placing a rubber ring around the urethra. Rats with bladder outlet obstruction were administered daily oral Eviprostat or vehicle, while sham operated animals were treated with vehicle. On day 6 after surgery bladder weight, oxidative stress markers and proinflammatory cytokine levels as a measure of bladder inflammation, were determined and histological alterations noted. Functional contractility studies were performed with longitudinal bladder strips.

RESULTS

Bladder outlet obstruction led to a significant increase in bladder weight, oxidative stress markers and proinflammatory cytokine levels. Eviprostat significantly suppressed these increases without affecting bladder weight. Histological analysis showed increased detrusor muscle hypertrophy and increased numbers of collagen fibers with accompanying inflammatory infiltration in the bladder of vehicle treated bladder outlet obstruction animals. Eviprostat treatment was associated with suppression of these changes. Decreased responses of obstructed bladder strips to electrical stimulation and KCl were ameliorated by Eviprostat treatment.

CONCLUSIONS

Eviprostat mediated decrease of the increased oxidative stress and bladder inflammation caused by bladder outlet obstruction may contribute to the protection of bladder function.

Changes of bladder activity and connexin 43-derived gap junctions after partial bladder-outlet obstruction in rats

INTRODUCTION

We investigated changes of vesical gap junctions in relation to changes of the micturition reflex in rats with partial bladder-outlet obstruction (BOO).

MATERIALS AND METHODS

A total of 66 female Sprague-Dawley rats were divided into six groups: sham operation (control); 3, 14, and 28 days after BOO; and 3 and 28 days after relief of BOO lasting for a three-day period. Under urethane anesthesia, isovolumetric cystometry was performed on each group. Expression of mRNA for the gap-junction protein connexin 43 (Cx43) in the bladder was measured in each group. Immunohistochemistry using Cx43 antibody was also performed on the bladder after BOO.

RESULTS

The interval between bladder contractions was shorter in all of the other groups than in the control group. Expression of Cx43 mRNA was increased 3, 14, and 28 days after BOO (the peak increase was twofold), and three days after the relief of BOO, but it returned to the control level by 28 days after relief of BOO. Histologically, smooth muscle hypertrophy was detected in the bladder after BOO and punctate staining of the smooth muscle by Cx43 antibody increased after BOO.

CONCLUSION

These results suggest that partial BOO produces detrusor overactivity that may depend on increased intercellular communication via gap junctions in the bladder. Relief of BOO led to a decrease of Cx43 mRNA, but detrusor overactivity persisted in the chronic phase, suggesting a reversible change of vesical gap junctions and an irreversible change of bladder activity after BOO.

Effect of short-term outlet obstruction on rat bladder nerve density and contractility

1 The present study was designed to investigate the relationship between innervation density and contractile responses to field stimulation and exogenous agonists at early time points after induction of bladder outlet obstruction (BOO) in rats. 2 When compared with sham-operated animals, 1, 3 and 7 days of BOO were associated with a 75%, 80% and 90% increase of bladder weight. Field stimulation caused a frequency-dependent increase in force of contraction. The force of contraction was reduced at each frequency in BOO rats with the greatest decrease after 1 day and a gradual but incomplete recovery thereafter. In contrast, contractile responses to ATP, carbachol and KCl were markedly reduced after 1 day of BOO and fully recovered after 7 days. The neurofilament staining was not altered by 1 day of BOO, but gradually decreased with increasing duration of BOO reaching the lowest levels after 7 days. 3 We conclude that impaired cellular contractility seems to underlie the early reductions of field stimulation-induced contraction, possibly reflecting surgical trauma of the tissue. However, at later time points a reduced nerve density, possibly reflecting a partial denervation, appears to be the main reason for impaired contractile response to field stimulation.

Endocrine status affects bladder size and postvoid residual urinary volume in mice

Urine is one of the major media for intraspecific chemical communication in mice. The urination pattern is dependent both on the mice's hormonal and social status. The urination pattern and the morphology of the urinary tract were examined in mice following hormonal manipulations. In the first experiment, we compared pairs of intact and castrated males: intact males urinated earlier when exposed to a new environment, with a greater number of drops that were smaller than those of castrated males. In the second experiment, groups of intact males, castrated, testosterone-supplemented castrated, and isolated intact males were compared. The micturition pattern of isolated intact males consisted of numerous small droplets of urine, with a high volume of urine retained in the bladder after voiding. This also applied to grouped intact males and testosterone-treated castrated mice, while castrated mice voided a larger fraction of bladder content. Bladder weight was higher in intact males and testosterone-treated castrated males, as compared to castrated males. In the third experiment, ovary-intact and testosterone-treated intact females were compared. Testosterone-treated ovary-intact females retained a larger quantity of urine in the bladder and also had a larger bladder compared to ovary-intact females. Testosterone thus induces the morphological modifications of the urinary tract necessary for the dominant male urination pattern, which is an increase in postvoid urinary residual volume and bladder weight. As evidenced from the comparison of histological sections from intact, castrated, and testosterone-treated castrated males, the increase in bladder weight was mainly due to the bladder muscular mass.

Doxazosin Effects on Cholinergic and Adrenergic Responses in Rat Isolated Detrusor Smooth Muscle Preparations From Obstructed Bladder

We investigated the effect of doxazosin on cholinergic and adrenergic agonists responses in detrusor smooth muscle preparations from sham-operated and 2-week partially obstructed rat bladders. Male Wistar albino rats, 200-250 g, were randomly allocated to 4 experimental groups consisting of 12 animals each: sham-operated bladder, sham-operated bladder treated with doxazosin, partially obstructed bladder, and partially obstructed bladder treated with doxazosin. Partial outlet obstruction of the rat was surgically induced. The response to carbachol (10(-7)-10(-4) M), isoproterenol (10(-6)-10(-3) M), and 80 mM KCl were recorded. Carbachol caused concentration-dependent contractile responses in the detrusor smooth muscles from sham-operated and partially obstructed bladder. Isoproterenol produced concentration-dependent relaxation responses in the detrusor strips from all groups. Dose-response curves for carbachol and isoproterenol showed a shift to the left in rat detrusor smooth muscles from partially obstructed bladder when compared with the results obtained in detrusor muscles from sham-operated bladder. These responses were reversed to normal by doxazosin treatment in rat detrusor smooth muscles from partially obstructed bladder. KCl produced contractile responses in rat detrusor smooth muscles from all groups. The contractile responses to KCl were not significantly changed in all groups. We have shown that carbachol and isoproterenol responses were shifted to the left in rat detrusor smooth muscles from partially obstructed bladder and these responses were reversed by doxazosin treatment.

In vitro rat bladder function after neonatal estrogenization

PURPOSE

Experiments were done to evaluate the functional effects of neonatal diethylstilbestrol (DES) treatment on bladder function in male and female Noble rats.

MATERIALS AND METHODS

At 5 months after neonatal DES bladders were removed and weighed. Ventral and dorsal bladder strips were prepared to evaluate the effects of neonatal DES on contractile responses to electrical field stimulation, carbachol, adenosine triphosphate, phenylephrine and KCl. Relaxant responses to the catecholamines arterenol (norepinephrine), epinephrine and isoproterenol were also monitored.

RESULTS

Neonatal DES resulted in significant increases in bladder mass in males and females. Contractile and relaxant responses were largely unchanged by neonatal DES treatment and the only change observed was a decreased response of ventral strips from male neonatal DES rats to 4 and 8 Hz. stimulation. Ventral strips from male control and neonatal DES rats responded to field stimulation and carbachol with significantly greater responses than dorsal strips and were more sensitive to the relaxant actions of norepinephrine and epinephrine.

CONCLUSIONS

The data confirm that neonatal DES causes infravesical obstruction. However, in contrast to published reports of the effects of surgically induced mild outlet obstruction, neonatal DES treatment has little effect on in vitro bladder strip contractile or relaxant function. Thus, the neonatal DES treated rat does not seem to be a useful model in which to study the in vitro effects of partial outlet obstruction on the bladder.

Overactive bladder in the male patient: bladder, outlet, or both?

Generations of urologists have presumed that the cause of lower urinary tract symptoms (LUTS) in men is infravesical (prostatic) obstruction. When symptoms such as urinary urgency and frequency can't easily be explained directly by obstruction, secondary effects of obstruction on the bladder are identified as causative factors. Although to some extent this explanation may still be accurate, emerging concepts in the pathophysiology of LUTS in men may be at odds with these traditional explanations. The idea that primary bladder pathology may explain the symptom complex in at least one subset of men with LUTS has both experimental and clinical support. This review discusses the physiologic and clinical observations used to explain the mechanisms underlying LUTS. Specifically, this review focuses on two data sets: one supporting infravesical obstruction as the causative factor for LUTS, and another positing that a primary bladder abnormality is responsible.

Relationship of mass of obstructed rat bladders and responsiveness to adrenergic stimulation

PURPOSE

The effects of experimental partial bladder outlet obstruction on the bladder response to nerve stimulation and contractile agonists have been well characterized. Mildly obstructed bladders have small increases in mass and increased contractile responses to electrical field stimulation. More severely obstructed bladders become decompensated with large increases in mass and decreased functional responses. Little is known about relaxant mechanisms after obstruction. We investigated the relationship of the increase in rat bladder mass induced by outlet obstruction and responses to alpha and beta-adrenergic stimulation.

MATERIALS AND METHODS

Male Sprague-Dawley rats were divided into 3 groups, namely control, sham operated and obstructed. Surgical obstruction was done by tying a 2-zero silk ligature around the urethra. The ligature was placed around the urethra and removed in sham operated rats. At 2 and 6 weeks bladders from all groups were harvested, weighed and cut into strips. Contractile responses to electrical field stimulation and norepinephrine in the presence of propranolol were measured. Relaxant responses to norepinephrine and isoproterenol were measured after pre-contraction with KCl.

RESULTS

All strips from control and sham operated rats relaxed completely in response to norepinephrine. Obstructed bladders that weighed 2 to 3-fold more than control or sham operated bladders also relaxed. In contrast, bladders that were 5 to 10-fold heavier failed to relax by at least 50% in response to norepinephrine, independent of duration of bladder outlet obstruction. These were called nonresponders. Two week nonresponders relaxed completely in response to isoproterenol, but 6-week nonresponders did not, suggesting that the duration of decompensation is important. All nonresponders relaxed in response to pinacidil (Sigma-Aldrich Corp., St. Louis, Missouri). Nonresponders tended to contract in response to norepinephrine in the presence of propranolol. Strips from the other rats were less responsive, suggesting an increase in alpha1-receptors with decompensation. Contractile responses to field stimulation were increased in obstructed strips that relaxed to norepinephrine, while responses of nonresponders were decreased compared with controls and sham operated rats.

CONCLUSIONS

Severely obstructed bladders had an increase in mass and a decreased response to field stimulation, indicative of decompensation. This response was accompanied by decreased ability to relax to beta-agonists and an increased response to alpha-agonists. These changes were not seen in smaller, compensated bladders. Our findings suggest a change in detrusor alpha1 and beta-adrenergic receptor density. An increase in detrusor alpha-receptors may explain the clinical efficacy of alpha-blockers in alleviating irritative voiding symptoms in men with benign prostatic hyperplasia.

Modulation of insulin-like growth factor-I system of the bladder using a somatostatin analogue in chronic spinalized rats

PURPOSE

We have previously reported the possible role of the insulin-like growth factor-I (IGF-I) system of mitogens in the development of detrusor smooth muscle hyperplasia and hypertrophy after spinal cord injury. We evaluated the in vivo effects of the anti-growth factor somatostatin analogue octreotide on the IGF-I system as well as subsequent changes in bladder smooth muscle hypertrophy and function after spinal cord injury in rats.

MATERIALS AND METHODS

Included in this study were 90 adult female Sprague-Dawley rats weighing 200 to 250 gm. Of the rats 18 served as sham operated controls, while the remaining 72 underwent were spinal cord transection at the level of the T10 vertebra. The spinalized animals were randomly divided into 4 equal groups of 18, of which 1 group served as paraplegic controls. The other 3 groups received octreotide (60 microgram. daily for 4 weeks) delivered via a subcutaneously implanted osmotic pump immediately, 2 and 4 weeks after spinal cord injury. At the end of the experiment (6 to 8 weeks) each group of animals was subdivided into 2 subgroups of 9. In the first group filling cystometrography was done, while in the second subgroup wet bladder weight was estimated and Northern blot analysis was performed.

RESULTS

Mean wet bladder weight plus or minus standard deviation in sham operated and paraplegic controls was 0.11 +/- 0.01 and 0.64 +/- 0.33 gm., respectively (p <0.05). The increase in bladder weight in paraplegic controls was associated with over expression of the IGF-I gene and with marked suppression of IGF binding proteins-3 and 5 compared with sham operated controls. On the other hand, mean wet bladder weight in the animals that received octreotide immediately after spinal cord injury was 0.17 +/- 0.02 gm., which was associated with a dramatic decrease in IGF-I gene expression and increased expression of IGF binding proteins-3 and 5. Mean cystometric bladder capacity in paraplegic controls was 0.48 +/- 0.18 ml. with an associated voiding pressure of 71 +/- 13 cm. water. All paraplegic controls showed detrusor hyperreflexia. In animals that received octreotide immediately after spinal cord injury mean cystometric bladder capacity was 2.49 +/- 1.75 ml. with an associated voiding pressure of 32 +/- 7 cm. water. Detrusor hyperreflexia disappeared in 88.89% of the rats in this group. There were less marked changes in bladder weight (mean 0.24 and 0.29 +/- 0.3 gm.), IGF-I gene expression and its binding proteins and urodynamic parameters when the drug was given 2 and 4 weeks, respectively, after spinal cord injury.

CONCLUSIONS

Modulating the IGF-I system of mitogens in detrusor smooth muscle with consequently decreased bladder hypertrophy and improved urodynamic behavior in spinal cord injured animals using somatostatin analogue could be a possible therapeutic modality in patients with spinal cord injury.

Early molecular changes in bladder hypertrophy due to bladder outlet obstruction

OBJECTIVES

To determine the temporal relationship between the increase in bladder mass and the expression of growth-associated gene products during bladder hypertrophy due to partial bladder outlet obstruction.

METHODS

Adult female rats, subjected to partial bladder outlet obstruction, were killed at defined points, and their bladder weight and total protein were determined and compared with sham-operated and nonoperated controls. Hyperplasia was determined by the expression of proliferating cell nuclear antigen, transcription factors, and cyclins in obstructed rat bladders. Bladder protein was fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and expression of the indicated proteins was determined by Western analysis and immunohistochemistry.

RESULTS

The mean bladder weight in sham-operated rats remained at 127 +/- 17 mg, and the weight in the obstructed animals increased to 239 +/- 56 mg at 12 hours, increasing to 486 +/- 168 mg by 168 hours. The total bladder protein increased 1.8-fold after 12 hours and continued to increase for the duration of obstruction. The expression of proliferating cell nuclear antigen in the obstructed group did not begin until 24 hours of obstruction. The expression of the transcription factors, upstream binding factor, and c-Jun followed a similar pattern. Cyclin E and C expression increased most significantly after 48 hours.

CONCLUSIONS

Bladder growth after 12 hours of partial outlet obstruction represents cellular hypertrophy based on the increases in bladder weight and total protein accumulation. Cellular hyperplasia occurs after 24 hours of obstruction as represented by increases in transcription factors and cell cycle-specific proteins.

Changes in detrusor and urinary growth factors according to detrusor function after partial bladder outlet obstruction in the rat

OBJECTIVES

To investigate the changes in detrusor and urinary growth factors according to detrusor function after partial bladder outlet obstruction in the rat. Growth factors have been reported to play a role in the remodeling of the bladder after obstruction.

METHODS

Female rats (n = 40) were used and divided into three groups: sham-operated control, 2-week mild obstruction, and 2-week severe obstruction. The voided urine was collected and the detrusor contractility to electrical stimulation recorded. mRNA expression and the urinary concentration of transforming growth factor beta-1 (TGF-beta1) and basic fibroblast growth factor (bFGF) were analyzed.

RESULTS

The contractile response to electrical stimulation was increased in the mild obstruction group (P <0.05) but decreased in the severe obstruction group (P <0.05). The detrusor mRNA expression of TGF-beta1 in the mild obstruction group was not different from that in the control group. However, in the severe obstruction group, the mRNA expression of TGF-beta1 increased. The detrusor mRNA expression of bFGF was gradually increased in the mild and severe obstruction groups. The urinary concentration of TGF-beta1 in the mild obstruction group was not significantly different from that in the control group. However, in the severe obstruction group, the concentration of TGF-beta1 was significantly increased (P <0.05). The concentration of urinary bFGF was too small to compare the results in each group.

CONCLUSIONS

Growth factors such as TGF-beta1 and bFGF change in mRNA expression according to bladder function, and urinary TGF-beta1 reflects the change of detrusor mRNA. Thus, changes in TGF-beta1 may be a marker to evaluate detrusor function.

Effects of verapamil on bladder instability induced by partial outflow obstruction in rat

BACKGROUND

Overactivity of the detrusor due to benign prostatic hyperplasia may be induced by hyperpermeability of the smooth muscle cell membrane to calcium. We investigated the effect of verapamil, a calcium channel blocker, on detrusor function in outflow obstructed and control rat bladders.

METHODS

Verapamil was injected intravenously via a catheter inserted into the internal jugular vein in doses of 0.5, 1.0, 2.0, 4.0, and 10.0 mg/kg in rat bladders with and without partial outflow obstruction under urethane anaesthesia. The intravesical pressure was monitored continuously. We measured the tidal voided urine volume, the voiding pressure, the pressure at which micturition was induced, and the end-point pressure of micturition.

RESULTS

The tidal voided urine volume was significantly decreased in the obstructed bladders before administration of verapamil. Verapamil had similar effects in cystometric parameters in obstructed and control bladders. Verapamil increased the tidal voided urine volume, the pressure at which micturition was induced, and the end-point pressure of micturition, and reduced the voiding in obstructed and control bladders. Verapamil at doses of 4.0 mg/kg or higher induced significant arrhythmia.

CONCLUSIONS

Verapamil reduced the contractile force of the bladder and increased the capacity and residual urine volume in both normal and obstructed bladders. Thus, although calcium channel blockers such as verapamil may be effective in treating a hyperactive bladder, they may have adverse cardiovascular effects.

Experimental bladder instability following bladder outlet obstruction in the female rat

PURPOSE

In rats, urethral obstruction was previously shown to lead to detrusor instability, but bladder instability in conscious animals has not been well characterized. The present study was designed to describe the consequences of bladder outlet obstruction on urodynamic parameters in the conscious rat. A categorization of different types of bladder instability in conscious rats is described.

MATERIALS AND METHODS

Cystometry was performed on conscious animals with chronically implanted lines. Recordings of the micturition pattern and the bladder pressure during the micturition cycle were made from normal female rats and those with instability caused by infravesical outflow obstruction.

RESULTS

In control rats, the peak micturition pressure was low (45.6+/-2.5 cm. H2O) and only small pressure fluctuations occurred before or after micturition. Rats with outlet obstruction exhibited bladder hypertrophy, high micturition pressure (95.5+/-6.8 cm. H2O) as well as marked spontaneous activity throughout the micturition cycle. According to the spontaneous activity profile we identified four main patterns of abnormal micturition cycles.

CONCLUSION

Urethral obstruction in rats leads to a significant increase in bladder weight and to altered micturition patterns which reveal clear similarities with features of the cystometric profiles performed in men with infravesical outflow obstruction. These modifications are not consistently correlated with an increase in bladder weight.

In vitro functional properties of the rat bladder regenerated by the bladder acellular matrix graft

PURPOSE

To assess the response of rat urinary bladder regenerated by the homologous bladder acellular matrix graft (BAMG) to in vitro electrical and pharmacologic stimuli.

MATERIALS AND METHODS

In Sprague-Dawley rats, partial cystectomy (>50%) was performed, followed by BAMG augmentation cystoplasty. After 4 months, organ bath studies of tissue strips in 10 were used to compare the contractility of the BAMG regenerates and the corresponding host detrusor smooth muscle.

RESULTS

The BAMG regenerates exhibited contractile activity to electrical field stimulation and a qualitatively identical pattern of response to muscarinic, purinergic, alpha- and beta-adrenergic drug administration and nitric oxide. At 4 months after surgery, the maximum forces of contraction of the BAMG regenerates to carbachol stimulation amounted to close to 80% of the host bladder response. With electrical field stimulation, they equaled 44% and 62% of the host bladder response after 2.5 and 4 months, respectively. Histological and immunohistochemical studies confirmed the presence of receptors for neurotransmitters that these functional in vitro studies implied.

CONCLUSIONS

The present study provides further evidence that augmentation cystoplasty with the BAMG leads to functional regeneration of the rat bladder detrusor smooth muscle.

Alterations in constituent urinary proteins in response to bladder outlet obstruction in rats

PURPOSE

Benign prostatic hyperplasia, resulting in bladder outflow obstruction, induces well recognized clinical symptoms and morphologic bladder changes. Despite these phenomenon, relatively little is known with regard to the precise molecular events occurring in the bladder as a consequence of obstruction. In an effort to screen for alterations in bladder gene expression induced by obstruction, and/or alterations in uroepithelial integrity, this study compared pre- and post-obstructive constituent urinary proteins in an animal model.

MATERIALS AND METHODS

Outlet obstruction was created using a previously established model system. Experimental animals were surgically obstructed for either 2 or 7 days, at which time the urine was aspirated and the bladders removed and weighed. Urinary proteins were separated using 2-D PAGE. Following comparison of sham versus experimental animals, microsequencing was performed on proteins that were down regulated.

RESULTS

Duplicate experiments confirmed the presence of outflow obstruction. Statistically significant increases (p <0.01) in bladder weights were seen at 2 and 7 days in the obstructed groups as compared with both sham and control groups. 2-D PAGE demonstrated a down regulation of three urinary proteins post-obstruction. Microsequencing identified these proteins as prostatic steroid-binding protein C3 precursor (pI=5.5, MW=15000), glandular kallikrein 9 (S3) precursor (pI=6.2, MW=19000), and glandular kallikrein 8 (P1) precursor (pI=6.2, MW=33000).

CONCLUSIONS

Bladder outflow obstruction alters constituent urinary protein composition in an animal model system. The precise etiology of these alterations remains to be defined.

Change in bladder contractility associated with bladder overactivity in rats with cerebral infarction

PURPOSE

To evaluate the contractile properties of overactive bladder from rats in the chronic stage of experimental cerebral infarction.

MATERIALS AND METHODS

Cystometry was performed in conscious male S-D rats after inducing occlusion of the left middle cerebral artery. Bladder muscle strips were evaluated for force development in response to field stimulation, acetylcholine and KCl. By measuring the contractile response to field stimulation after adding atropine and alpha,beta-methylene-ATP, contributions of cholinergic and purinergic transmission were determined.

RESULTS

Bladder capacity of cerebral-infarcted rats was <50% of the capacity of sham-operated rats and significantly less than that of sham-operated rats even 4 months after surgery. There was no significant difference in bladder weight between sham-operated rats and cerebral-infarcted rats. No differences in the contractile response of detrusor strips to field stimulation and acetylcholine, or in the relative contribution of cholinergic and purinergic transmission to the contractile response, were observed over time or between strips from sham-operated rats and cerebral-infarcted rats. KCl induced significantly less contraction in strips from 4 month infarcted rats than in strips from 4 month sham-operated rats, 2 week infarcted rats and 2 month infarcted rats.

CONCLUSIONS

This animal model will be useful for chronic studies on the mechanism of detrusor hyperactivity (DH).

Effect of ischemia and partial outflow obstruction on rat bladder function

We investigated the effects of ischemia induced by ligation of the bilateral internal iliac arteries following partial outlet obstruction on changes in detrusor function in rat. Rats were divided into three groups: sham-operated control rats, rats with partial outlet obstruction, and rats with obstruction+ischemia. Bladder function was studied by the in vitro organ bath technique 7 days after surgery. The weight of the bladder was significantly increased in both the obstruction and obstruction+ischemia groups. The obstruction+ischemia group exhibited a greater increase in weight. The passive length-tension relationship of detrusor muscle strips showed that tissue elasticity was decreased and the active length-tension relationship demonstrated that the peak response was observed at a shorter tissue length in the obstruction+ischemia group compared with the other two groups. There was no difference in the passive and active length-tension relationships between the control group and the obstruction group. The contractile response to various kinds of stimulation (field stimulation, bethanechol, ATP, and KCl) increased in the obstruction group and decreased in the obstruction+ischemia group. These findings suggest that partial outflow obstruction alone increased bladder contractility in response to stimuli. However, ischemia reduced the contractility and elasticity of the bladder wall.

Restoration of rat bladder function following release of short- and long-term partial outflow obstruction

Detrusor dysfunction does not recover in some patients with benign prostatic hyperplasia (BPH) even after prostate resection. 'We studied the functional restoration of the rat bladder after release of short- or long-term outflow obstruction. Bladder function was assessed by in vivo infusion cystometry and an in vitro organ bath technique. There were no significant differences in bladder weight and contractile strength induced by stimuli in detrusor muscle strips from obstructed rats and age-matched control rats. After short-term obstruction the whole bladder pressure generated in vitro by field stimulation, bethanechol, ATP, and KCl completely recovered to control levels. In contrast, after long-term obstruction, the whole bladder pressure in response to field stimulation remained significantly lower than in controls. Infusion cystometry variables, including the pressure at which micturition was induced, maximal voiding pressure, capacity, and residual urine volume, were similar between controls and rats subjected to short-term obstruction. However, the maximal voiding pressure after long-term obstruction was significantly less than that of controls.