Increase In Bladder Mass Research Articles

Diabetes Mellitus Increases the Rate of Development of Decompensation in Rats With Outlet Obstruction

We investigated the effects of the combination of bladder outlet obstruction and diabetes mellitus on in vitro rat bladder body strip function. Longitudinal strips were removed from ventral and dorsal detrusor of age matched control, 2-week diabetic, 2-week obstructed and 2-week obstructed diabetic rats. Contractile responses to electrical field stimulation, carbachol, adenosine triphosphate, KCl and phenylephrine, and relaxations in response to norepinephrine and isoproterenol were measured. Bladders from diabetic, obstructed and obstructed diabetic rats were 1.6-fold, 2.6-fold and 3.6-fold heavier than those from controls. Responses of bladder strips from diabetics to all stimuli were similar to those of controls. Strips from obstructed rats were significantly less responsive to norepinephrine than those from controls or diabetics and strips from obstructed diabetics were significantly less responsive to norepinephrine and isoproterenol than those from all other groups. Strips from obstructed diabetics had significantly decreased responses to field stimulation, while responses to carbachol were decreased to a lesser extent. Responses of strips from obstructed rats to field stimulation were also decreased compared with controls but were significantly greater than those of the obstructed diabetic group. Responses to adenosine triphosphate, KCl and phenylephrine were similar in all groups. The combination of outlet obstruction and diabetes mellitus causes significant increases in bladder mass compared with either diabetes or obstruction alone. Bladder strips from obstructed diabetics show characteristics of denervation accompanied by alterations in beta-adrenergic function, suggesting that the coexistence of outlet obstruction and diabetes increases the rate of development of bladder decompensation.

Lower urinary tract symptoms/benign prostatic hyperplasia: maintaining symptom control and reducing complications

Because the average patient with lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH), or LUTS/BPH, has a remaining life expectancy of 15 to 20 years, both short-term and long-term outcomes matter in the management of LUTS/BPH. Sustained symptom control and improvement of quality of life (QOL), control of disease progression (ie, prevention or reduction of bladder wall hypertrophy [BWH]/increased bladder mass and reduction of the risk of serious complications), and minimization of the need to switch to other medical therapy or surgery are important. In this respect, α 1-adrenoceptor antagonists, such as tamsulosin, have been shown to provide effective and rapid relief of symptoms and improvement in QOL, which is sustained in the long term (up to 6 years). Obstruction may, in the long term, induce changes in the bladder wall (eg, BWH), which may result in (irreversible) bladder damage and serious complications. Preliminary data suggest that α 1-adrenoceptor antagonists prevent the development of BWH in rabbits and reduce existing BWH in obstructed LUTS/BPH patients. Pooled analyses and indirect comparisons of clinical studies up to 1 year have shown that α 1-adrenoceptor antagonists, such as tamsulosin, reduce the risk of acute urinary retention and the need for surgery to at least the same extent as the 5α-reductase inhibitor finasteride. In addition, monotherapy with an α 1-adrenoceptor antagonist reduces the risk of long-term clinical progression; the combination with finasteride may be more beneficial in patients at high risk (patients with large prostate volume, high level of prostate-specific antigen, high International Prostate Symptom Score, high postvoid residual amount, and low maximum flow rate). Therefore, α 1-adrenoceptor antagonists, such as tamsulosin, are first-line therapy, not only in the short term but also in the long-term management of LUTS/BPH.

Bladder smooth muscle cell phenotypic changes and implication of expression of contractile proteins (especially caldesmon) in rats after partial outlet obstruction.

The purpose of the present study was to investigate morphological changes in bladder smooth muscle of rats with partial outlet obstruction. We investigated smooth muscle cell phenotypic changes and implication of synthetic phenotype in contractility decrease and bladder compliance after bladder outlet obstruction. Partial bladder outlet obstruction was introduced in female rats. Bladder were removed at 1, 3, 6, 10 and 20 weeks after the obstruction. Temporal pattern of changes in bladder mass, light microscopic pathogenesis and phenotypic expression of the bladder smooth muscle cells in the electron micrographs were investigated. Expression of contractile protein was also investigated by the immunoblotting method. Marked increase in bladder mass with marked thickening of smooth muscle layer was observed at 1 week after obstruction. The ratio of myocytes exhibiting contractile and synthetic phenotypes was almost constant until 6 weeks after the obstruction, but thereafter, synthetic phenotypes gradually increased and the ratio (synthetic/contractile phenotype) was 1.5-fold at 20 weeks after the obstruction. Caldesmon was most markedly expressed after the obstruction among contractile proteins examined by the immunoblotting method. Phenotypic changes were confirmed in bladder smooth muscle, and the decrease of the ratio of contractile phenotype was observed after long-term obstruction of the bladder outlet. Among the contractile proteins in the bladder smooth muscle cell, caldesmon was considered a reliable marker for predicting the pathogenetic conditions of the bladder.

Murine in vitro whole bladder physiology.

The function of the bladder is twofold: 1) to store urine at low pressure, and 2) under control of the nervous system, to generate a contractile force coordinated with a lowered urethral resistance that allows for emptying.20 Clinically, this system is most commonly affected by bladder outlet obstruction, and the response of the detrusor is remarkable in its variability. Experimentally, most investigators agree that after outlet obstruction, there is an increase in bladder mass seen irrespective of the model used. Within most experimental models of partial obstruction (as with humans), there exists a degree of variability in terms of detrusor response. Some bladders enter a state of compensation and are able to sustain elevated voiding pressures and empty satisfactorily. Others enter a state of decompensation and lose their ability to empty effectively.15 The molecular mechanisms for such decompensations are under current investigation, and may involve alterations in cytosolic calcium handling,19,21 disruptions in mitochondrial function,4 and changes in the expression of contractile filaments.1 In the late stages, as the bladder slides into the decompensated state, major depositions of extracellular matrix are seen in a variety of species.3,9,11

Focal hypoxia of the obstructed rabbit bladder wall correlates with intermediate decompensation.

We showed that partial obstruction of the rabbit bladder outlet caused decreases in detrusor blood flow that were directly proportional to the level of decompensation present. Bladder decompensation is characterized by decreases in detrusor contractility, mitochondrial function, and sarco/endoplasmic reticulum calcium ATPase (SERCA) activity in obstructed rabbits. The current study was designed to create bladder decompensation and to relate its characteristic dysfunctions to the presence or absence of hypoxia in the obstructed rabbit bladder wall. Tissue hypoxia was visualized immunohistochemically after administration of a hypoxia probe in vivo. Twelve New Zealand White rabbits were separated into two groups. The rabbits in group 1 received sham operations; the rabbits in group 2 received partial outlet obstructions by standard methods. Four weeks after surgery, each rabbit received an intraperitoneal injection of aqueous Hypoxyprobe-1, which forms protein adducts in cells having O(2) concentrations less than 14 microM. Two hours after injection, the rabbit was anesthetized and the bladder exposed through a midline incision. One full-thickness bladder strip was cut and immediately placed in fixative for immunohistochemical recognition and visualization of Hypoxyprobe-1-protein adducts. The remaining bladder was then excised, and three additional strips were cut for contractility studies. The remainder of the bladder was frozen for biochemical and slot-blot analyses. Bladder weight was increased fourfold after obstruction, and significant contractile and biochemical dysfunctions were observed that indicated an intermediate level of decompensation. Immunohistochemical visualization revealed focal areas of moderate to severe hypoxia in the detrusor smooth muscle (SM) and subserosal regions of these bladders. No hypoxia was observed in the obstructed bladder mucosa, consistent with the absence of biochemical dysfunction in this compartment, or in unobstructed bladders. Slot-blot analyses confirmed the presence of significant Hypoxyprobe-1-protein adducts in the detrusor of the obstructed bladder, whereas none were present in the control bladder detrusors. Partial outlet obstruction of rabbit bladders resulted in focal areas of moderate to severe hypoxia in the detrusor SM and subserosal regions concomitant with increased bladder mass, decreased contractile function, and selective metabolic dysfunctions of the SM consistent with an intermediate stage of decompensation. The metabolic characteristics of the normoxic mucosa were normal a were those of unobstructed bladders.

In Vitro Rat Bladder Function After Neonatal Estrogenization

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

LUTS, the Case Is Altered

Objective: To explore the current understanding, beliefs and perceptions of European urologists regarding the aetiology, diagnosis and management of lower urinary tract symptoms suggestive of benign prostatic hyperplasia (LUTS/BPH) and match them with current scientific literature and guidelines. Methods: European urologists with a European Association of Urology (EAU) membership and an e-mail address were invited to register with the urologist panel. Every newly registered urologist was validated and invited to complete a web-based survey. The results of the survey are presented by means of descriptive statistics. Results: In total, 119 European urologists from 27 countries were included in our analyses, of which 115 completed all questions. Most respondents agreed that besides obstruction, bladder instability, ageing, co-morbidity and central nervous system disorders are also involved in the aetiology of LUTS. They believed that voiding symptoms are predominantly related to obstruction, and storage symptoms to bladder instability. Whether the latter is only due to bladder changes secondary to obstruction or also due to (upregulated) α 1D-adrenoceptor subtypes in the bladder remains controversial and should be further investigated, although the majority of the respondents believed that α 1-adrenoceptor antagonists blocking both α 1A- and α 1D-adrenoceptor subtypes directly target the prostate and the bladder. The respondents acknowledged the importance of bladder protection in the long-term management of LUTS/BPH for reducing the risk of serious complications. They did not consider an increased bladder mass a relevant risk factor for serious complications and did not recommend ultrasound estimated bladder weight (UEBW) as a diagnostic test. Furthermore, prostate size was not perceived as a risk factor, in marked contrast to the published literature. Main elements in the current risk evaluation are post-void residual urine volume, urinary flow and symptom severity. Both transurethral resection of the prostate (TURP) and α 1-adrenoceptor antagonists were considered effective for the relief of voiding and storage symptoms with TURP having a greater effect on voiding symptoms, whereas the effect on storage symptoms of both treatments was appreciated as similar. TURP was perceived as the most effective treatment for reducing obstruction and the risk of acute urinary retention (AUR). “Selective α 1-adrenoceptor antagonists (e.g. tamsulosin)” and phytotherapy were considered the best tolerated treatments. Finally, the respondents believed that patients at risk for serious complications may benefit from long-term treatment with α 1-adrenoceptor antagonists. Conclusions: The results of this survey show that the respondents were familiar with new concepts in the aetiology and management of LUTS/BPH, so it seemed that a paradigm shift is present among European urologists. The results give us an idea about the future directions in the management of LUTS/BPH. The most striking finding of this survey seems to be the lack of clarity over the significance of an increased bladder mass in the long-term management of LUTS/BPH. More research, especially regarding long-term complications, is needed to provide better insight into this and to find out who should be treated, for how long, with which type of treatment and when treatment should be started to prevent/reduce serious complications.

Obstructive Bladder Dysfunction: Morphological, Biochemical and Molecular Changes

Obstruction can cause changes in bladder structure and function, which may at a certain point in time become irreversible. Both the rabbit and the rat have proven to be excellent models to study the morphological, biochemical and molecular changes that occur in the bladder following obstruction. Similarities between partial outflow obstruction in animals and obstructive dysfunction in man include increased bladder mass, increased fibrosis, reduced compliance, increased incidence of detrusor instability and decreased contractile ability. Obstructed bladder function can remain relatively normal for prolonged periods of time, even though bladder mass is increased (compensated stage). If the obstruction is not relieved, bladder function destabilizes and then decompensates, with subsequent risk of serious complications. It is hypothesized that the shift from the compensated to the decompensated stage is related to cyclical periods of ischaemia followed by reperfusion (I/R). This initiates degenerative membrane effects, which supports the process of bladder decompensation. It seems that relief of obstruction during the compensated stage, at least in animals, can induce a rapid and full restoration of the bladder function. However, if the obstruction is relieved during the decompensated phase, bladder function only partially recovers. Irreversible bladder decompensation may be prevented by reducing increased bladder mass and/or by reducing ischaemia/increasing blood supply to the bladder. The antioxidant Vitamin E seems to reduce the progression of decompensation in rabbits. Treatment of rats with the α 1-adrenoceptor antagonist doxazosin prior to partial outlet obstruction increases blood flow to the bladder, significantly decreases the effect of obstruction on bladder weight, and significantly protects the contractile function of the obstructed bladder. Pre-treatment of rabbits with the α 1-adrenoceptor antagonist tamsulosin partly prevents the development of bladder wall hypertrophy due to obstruction. In conclusion, there is evidence that I/R plays an important role in the pathogenesis of obstructive bladder dysfunction. Therefore, I/R should be prevented or relieved. As I/R is the consequence of increased bladder mass following obstruction, therapies that prevent or reduce increased bladder mass (such as the α 1-adrenoceptor antagonist tamsulosin) are likely to protect the bladder from (further) dysfunction. Therapies based on both the relief of I/R (increasing blood flow to the bladder, e.g. α 1-adrenoceptor antagonists) and preventing I/R induced cellular damage (e.g. antioxidant activity) have been shown experimentally to significantly reduce the severity of bladder dysfunction secondary to partial outflow obstruction. Of course, these potentially useful and novel mechanisms of action of therapy should also be investigated in humans.

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.

Partial outlet obstruction of the rat bladder induces a stimulatory response on proliferation of the bladder smooth muscle cells.

Outlet obstruction of the rat bladder induces hypertrophy/hyperplasia characterized by increases in bladder mass, smooth muscle content, and collagen deposition. In order to understand the mechanism of the outlet obstruction-induced hypertrophy and hyperplasia, we first determined the temporal pattern of changes in bladder mass after inducing the outlet obstruction. Histological analysis revealed that the smooth muscle cells with hypertrophy and hyperplasia, fibroblasts and connective tissue were increased in a time-dependent manner, corresponding to the temporal pattern observed in the changes in bladder mass, although the phase of changes in these tissue components was somewhat different. In order to further determine whether any proliferation-stimulatory factors were released from the bladder with obstruction in correspondence with increased bladder mass, soluble fractions were prepared from the bladders with outlet obstruction for 3-30 weeks, and their effects on proliferation of smooth muscle cells were examined. The soluble fractions prepared from the bladders at 3 to 14 weeks after obstruction slightly but significantly facilitated the proliferation of cultured smooth muscle cells, while the soluble fractions released after 20 weeks rather suppressed the proliferation. These results suggest that the initial increase in bladder mass might be in part due to the facilitated proliferation of smooth muscle cells of the bladder body induced by growth factors released into the soluble fractions, and that hypertrophy might then play a role in the increased bladder mass at later phases.

Aspirin treatment improves bladder function after outlet obstruction in rabbits

Objectives. To examine whether bladder smooth muscle dysfunction after outlet obstruction could be altered by treatment with aspirin. Long-term outlet obstruction causes contractile and metabolic dysfunction of the bladder in vivo and in vitro. The evidence is growing that a decrease in bladder perfusion is an important cause of this phenomenon. The platelet aggregation inhibitor, acetylsalicylic acid (aspirin), has been used to improve perfusion of the heart for decades. Methods. Ten male New Zealand white rabbits were obstructed for 4 weeks. Five rabbits received no further treatment (Obs), and 5 rabbits received 2 mg/kg/day aspirin (Obs+aspirin), administered by an osmotic pump implanted subcutaneously 1 week before the surgical obstruction. The bleeding time was measured to confirm the effectiveness of the aspirin treatment. Three different control groups were created: sham-operated rabbits, unobstructed rabbits with pumps containing DMSO (vehicle), and unobstructed rabbits with pumps containing aspirin. The contractile responses of bladder strips to field stimulation, adenosine triphosphate, carbachol, and KCl were determined. A section of each detrusor tissue was fixed in formalin and used to determine the smooth muscle and collagen (connective tissue) volume fraction. Results. No differences were found in the bladder weights or responses to stimuli in the different control groups, which were therefore combined. Partial bladder outlet obstruction caused significant increases in the bladder weight of the obstructed animals (Obs+aspirin, 10.15 ± 0.87 g; Obs, 10.17 ± 0.88 g; and controls, 2.87 ± 0.21 g). The aspirin treatment increased the bleeding time from 1.7 ± 0.3 minutes to 3.3 ± 0.1 minutes. The responses to field stimulation were significantly reduced in all of the obstructed rabbits. However, the responses of the bladder strips from the Obs rabbits to field stimulation were impaired to a significantly greater degree than were those from the Obs+aspirin rabbits. The response to 32-Hz stimulation was reduced by 86% in the Obs group but by only 64% in the Obs+aspirin group. The responses to carbachol were significantly reduced by 62% in the strips from the Obs rabbits, but the responses of the strips from the Obs+aspirin rabbits were similar to the responses of the strips from the controls. The responses to KCl and adenosine triphosphate were reduced, although they just failed to achieve statistical significance using Bonferroni’s analysis. The ratio of smooth muscle and connective tissue shifted slightly toward smooth muscle after 4 weeks of obstruction, but no difference was found with or without aspirin treatment. Conclusions. Low-dose aspirin has a small but significant protective effect on the contractile dysfunction induced by bladder outlet obstruction in rabbits, although the increase in bladder mass was not altered. Bladders of the same weight showed improved responses to all forms of stimulation after pretreatment with aspirin. Already used by millions of patients with heart diseases, aspirin could be a useful protection against contractile dysfunction of the obstructed bladder.

Vascular response of the rabbit bladder to chronic partial outlet obstruction.

Partial outlet obstruction of the rabbit urinary bladder results, initially, in a rapid increase in bladder mass and remodeling of the bladder wall. Previously, it was shown that this response was characterized by serosal growth (thickening) which was apparent after 1 day of obstruction, before any visible vascularization was observed. After 1 week of obstruction, significant microvessel formation was seen in the transition region between the detrusor smooth muscle and the thickening serosa; after 2 weeks the entire serosa was vascularized. In this study we investigated the effect of chronic (4 week) partial outlet obstruction on microvessel density and distribution in the bladder wall immunohistochemically using CD31 as a marker for vascular endothelium. Transverse sections of bladder wall were examined after 4 weeks of no surgery, sham surgery or partial obstruction. The microvessel density of the obstructed rabbit bladder mucosa and detrusor smooth muscle increased relative to augmentation of these compartments while new vessels appeared in the thickening serosa. Although vessel density did not change with obstruction a significant shift in mean vessel circumference to the left occurred indicating a significant increase in the number of microvessels and small vessels consistent with angiogenesis.

RABBIT URINARY BLADDER BLOOD FLOW CHANGES DURING THE INITIAL STAGE OF PARTIAL OUTLET OBSTRUCTION

The rabbit urinary bladder's early response to partial outlet obstruction includes bladder wall remodeling with marked urothelial and fibroblast hyperplasia (1 day) and smooth muscle hypertrophy (3-5 days) resulting in a 4-5 fold increase in bladder mass within 7 days. In this study, we examined the effect of partial outlet obstruction on bladder blood flow during the initial period of rapid growth (1-7 days). Each New Zealand White rabbit was partially obstructed by tying a 2-0 silk ligature loosely around the vesical outlet. After 0 (unoperated), 4 hours, 1, 3, or 7 days of obstruction, 5 rabbits per group were anesthetized and the carotid and femoral arteries cannulated with polyethylene tubing. Additional rabbits receiving sham surgeries were treated like obstructed animals at 4 hours and 1 day post-obstruction (5/group). Using standard methods, fluorescent microspheres were infused through the right carotid artery. Bladder and right kidney were rapidly removed upon completion of sphere infusion; bladder mucosa and muscle were separated. Sphere densities in detrusor, mucosa, and kidney were measured by Interactive Medical Technologies, Ltd. A section of each detrusor tissue was fixed in formalin and immunostained for smooth muscle alpha-actin. Mucosal blood flow (0.20 +/- 0.03 ml./min./gm.) was approximately 4-fold greater than that of detrusor (0.05 +/- 0.01 ml./min./gm.). Sham surgery caused a significant increase in bladder blood flow at 4 hours post-obstruction that returned to control levels by 1 day. Both mucosal and muscle blood flows were slightly higher in rabbit bladders obstructed for 4 hours than in sham-operated rabbits, and substantially greater in those obstructed for 1 day: 0.68 +/- 0.13 ml./min./gm. (mucosa) and 0.26 +/- 0.04 ml./min./gm. (muscle). Blood flows returned to control values by 3 days post-obstruction and remained constant through 7 days. Kidney blood flow was unchanged. Although bladder weight increased 4-fold after 7 days of obstruction, the volume fraction of smooth muscle (transverse section) remained constant at approximately 40%. Blood flow was approximately 4-fold greater in bladder mucosa than in muscle, which may relate to the significantly higher metabolic rate and lower high energy phosphate concentration of mucosa than muscle. Partial outlet obstruction resulted in a significant increase in blood flow at 1 day post-obstruction, which coincides temporally with the early cellular hyperplasia and hypertrophy of obstructed rabbit bladder. This increase in blood flow may be an essential factor for the initial increase in bladder mass. By three days, the blood flow per gram of tissue returned to control levels. The mechanisms relating to the changes in blood flow induced by partial outlet obstruction are currently under investigation.

Effects of partial bladder outlet obstruction and its relief on types I and III collagen and detrusor contractility in the rat

Bladder outlet obstruction induces a rapid hypertrophy characterized by increased bladder mass and collagen deposition. An increase in collagen is likely to reduce the contractility and compliance of bladder wall. This study was undertaken to investigate the effects of partial bladder outlet obstruction and its relief on types I and III collagen, and the relationship between detrusor contractility and collagen types. A total of 40 female rats was used for experiment and divided into one control, one obstruction, and three recovery groups. The contractility to field stimulation was recorded; total collagen and collagen concentration were quantified. The localization of types I and III collagen and the expression of pro-alpha1(I) and alpha1(III) collagen mRNA were determined by immunohistochemical staining and Northern blot hybridization, respectively. Contractile response to field stimulation was reduced after obstruction and recovered following relief. The total amount of collagen increased after obstruction and decreased after relief; however, collagen concentration decreased after obstruction and increased following relief. Contractility correlated negatively with total collagen but positively with collagen concentration. The protein deposition of types I and III collagen was localized in lamina propria and muscle bundles in all groups. The expression of types I and III collagen gene was up regulated after obstruction, but down regulated after relief. Negative correlation between contractility and gene expressions of collagen types was significant. These data suggest that the change in localization and quantity of collagen types leads to morphologic changes of bladder and can have an impact on the contractility of detrusor. Neurourol. Urodynam. 19:29-42, 2000.

INTERMITTENT CATHETERIZATION LIMITS RABBIT BLADDER DYSFUNCTION IN RESPONSE TO PARTIAL OUTLET OBSTRUCTION

The initial response of the urinary bladder to outflow partial obstruction consists of distension, followed by a rapid increase in mass and concomitant functional adaptations. Subsequently, an indeterminate period of stabilized function and little increase in mass occurs (compensation). Finally, bladder mass again progressively increases, accompanied by deleterious changes in bladder morphology, biochemistry and pharmacology, and progressive loss of function (decompensation). The reported study was designed to determine whether limiting the level of bladder distension, using intermittent catheterization (IntCath), could protect the bladder from decompensation. Sixteen male New Zealand White rabbits were separated into 4 groups of 4 rabbits each: control, control with IntCath, obstructed, and obstructed with IntCath. IntCath was performed with the animals under inhalation anesthesia. An 8 Fr. catheter was inserted through the urethra into the bladder every 8 hours and the urine drained. After 14 days of obstruction, bladders were removed from all rabbits; longitudinal strips were cut from the bladder body and suspended in individual organ baths. Contractile responses to field stimulation (FS), KCl, ATP, and carbachol were measured. There were no significant differences between control rabbits and controls with IntCath in bladder weights, compliance, and contractile responses to all stimuli. Bladder weights of both obstructed groups increased significantly compared to those of both control groups. Bladder weights of obstructed rabbits increased to a significantly greater extent than did those of obstructed rabbits with IntCath. Bladder compliance in the obstructed group was significantly lower than compliance in both control groups and in obstructed rabbits with IntCath. Both obstructed groups exhibited significantly decreased contractile responses to FS, ATP and KCl, compared to control groups. The response of the obstructed group with IntCath to FS and carbachol was significantly greater than the responses of the obstructed group without IntCath. These findings show that limiting distension with IntCath reduces the magnitudes of the increased bladder mass, the loss of bladder wall elasticity (compliance), and the impaired contractile responses which occur secondary to outflow obstruction.

Effects of partial bladder outlet obstruction and its relief on types I and III collagen and detrusor contractility in the rat.

Bladder outlet obstruction induces a rapid hypertrophy characterized by increased bladder mass and collagen deposition. An increase in collagen is likely to reduce the contractility and compliance of bladder wall. This study was undertaken to investigate the effects of partial bladder outlet obstruction and its relief on types I and III collagen, and the relationship between detrusor contractility and collagen types. A total of 40 female rats was used for experiment and divided into one control, one obstruction, and three recovery groups. The contractility to field stimulation was recorded; total collagen and collagen concentration were quantified. The localization of types I and III collagen and the expression of pro-alpha1(I) and alpha1(III) collagen mRNA were determined by immunohistochemical staining and Northern blot hybridization, respectively. Contractile response to field stimulation was reduced after obstruction and recovered following relief. The total amount of collagen increased after obstruction and decreased after relief; however, collagen concentration decreased after obstruction and increased following relief. Contractility correlated negatively with total collagen but positively with collagen concentration. The protein deposition of types I and III collagen was localized in lamina propria and muscle bundles in all groups. The expression of types I and III collagen gene was up regulated after obstruction, but down regulated after relief. Negative correlation between contractility and gene expressions of collagen types was significant. These data suggest that the change in localization and quantity of collagen types leads to morphologic changes of bladder and can have an impact on the contractility of detrusor. Neurourol. Urodynam. 19:29-42, 2000.

Sucrose diuresis protects rat bladder from outlet partial obstruction-induced contractile dysfunction

Objectives. Evidence is accumulating that bladder dysfunction caused by experimental partial obstruction of the bladder outlet can be reduced or reversed by treatment that results in upregulation of bladder function, even in the presence of obstruction. Inducing diuresis in rats or rabbits results in a significant increase in bladder mass and increased contractility in response to stimulation. The objective of the present study was to determine whether diuresis-induced amplification of bladder function in the rat could protect the bladder from contractile dysfunctions caused by partial outlet obstruction. Methods. Thirty-two rats were separated into four groups of 8 rats each. Groups 2 and 4 were fed 5% sucrose instead of water; groups 1 and 3 were fed only water. Three weeks later, partial outlet obstructions were created in groups 3 and 4. After 4 weeks of obstruction, all bladders were rapidly excised and cut into longitudinal strips; each strip was mounted in an isolated muscle bath for contractile studies. Results. Sucrose-induced diuresis caused a moderate but significant increase in bladder mass. Partial outlet obstruction stimulated significant increases in bladder mass in both water-drinking and sucrose-drinking groups; the bladder mass of sucrose-drinking rats, however, increased less than that of water-drinking rats. In water-drinking rats, partial outlet obstruction resulted in significantly decreased bladder strip contractility in vitro in response to field stimulation (1 to 32 Hz), carbachol (0.1 to 22 μM), and KCl (120 mM). After 3 weeks of sucrose-induced diuresis, partial obstruction of the rat bladder outlet did not result in decreased in vitro contractile responses to any form of stimulation applied. Conclusions. Sucrose-induced diuresis caused an increase in bladder mass and an increase in contractile strength, consequently protecting the rat bladder from the contractile dysfunctions that usually follow partial outlet obstruction.

Metabolic basis for contractile dysfunction following chronic partial bladder outlet obstruction in rabbits.

Prior studies have shown that partial outlet obstruction of the rabbit bladder causes a progressive increase in bladder mass, a progressive decrease in the contractile response to different forms of stimulation, and a selective decrease in the activity of mitochondrial enzymes. In this investigation the contractile responses to field stimulation and bethanechol were directly correlated with the activity of citrate synthase as a function of both the duration of obstruction and the bladder mass. Partial bladder outlet obstruction was surgically induced in twenty New Zealand White rabbits. The bladders were then rapidly excised at 30, 40, 90, 105 or 150 days post obstruction. The contractile responses to field stimulation (32 Hz) and bethanechol (250 microM) were determined. The remainder of the bladders were frozen and used for citrate synthase activity determinations. The data were grouped for analysis both by the duration of obstruction and by the bladder mass. Chronic partial outlet obstruction caused a parallel decline in the activity of citrate synthase and in the response of the obstructed tissue to stimulation.

Mitochondrial involvement in bladder function and dysfunction.

Benign bladder pathology resulting from prostatic hypertrophy or other causes is a significant problem associated with ageing in humans. This condition is characterized by increased bladder mass, decreased urinary flow rate, decreased compliance, and these and other changes in bladder function often subject patients to increased risk of urinary tract infection. While the physiologic attributes of benign bladder pathology have been extensively described in humans and in various animal model systems, the biochemical and molecular genetic bases for that pathology have only recently been investigated in detail. Studies demonstrate that mitochondrial energy production and utilization are severely impaired in bladder smooth muscle during benign bladder disease, and to a large extent this realization has provided a rational basis for understanding the characteristic alterations in urinary flow and compliance in bladder tissue. Recent investigations targeting the detailed molecular basis for impaired mitochondrial function in the disease have shown that performance of the organellar genetic system, and to a large extent that of relevant portions of the nuclear genetic system as well, is severely aberrant in bladder tissue. In this article, we discuss the physiologic aspects of benign bladder disease, summarize biochemical evidence for the altered mitochondrial energy metabolism that appears to underlie bladder pathology, review the structure and function of the mitochondrial genetic system, and discuss molecular genetic studies of that system which have begun to provide a mechanistic explanation for the biochemical and physiological abnormalities that characterize the disease. We also discuss areas for further research which will be critically important in increasing our understanding of the detailed causes of benign bladder pathology.

Use of abdominal fascia to create partial outlet obstruction in rabbits.

Partial outlet obstruction has been used for a considerable period of time as an animal model for the urodynamic changes that occur with the progressive obstruction of benign prostatic hyperplasia (BPH). Although there are many models of partial outlet obstruction, one common feature is that the degree of obstruction produced is inconsistent. The current study evaluates the responses of the bladder to a partial outlet obstruction created using an autologous fascial collar from harvested rectus fascia. The results demonstrate that although there was a moderate and variable increase in bladder mass, the alterations in the contractile responses to field stimulation (FS), carbamyl choline (carbachol), KCl, and adenosine 5'-triphosphate (ATP) were less severe than other models of partial outlet obstruction. Specifically, there was an approximate 40% decrease in the magnitude of the contractile response to FS but no significant changes in the magnitude of the contractile responses to carbachol, KCl, or ATP. Further analysis of the contractile responses demonstrated that there was a greater decrease in the rate of tension generation than in the magnitude of response for FS, and a significant increase in the time to maximal tension. Although there were no decreases in the magnitude of the responses to carbachol, KCl, or ATP, there were significant reductions in the rate of tension generation for carbachol and KCl and significant increases in the time to maximal tension for carbachol and ATP. Applying less tension over a wider area, the fascial collar provided a consistent and reproducible mild partial outlet obstruction.