Kohki tea protects the rabbit bladder from ischemia/reperfusion-induced contractile dysfunction.

OBJECTIVES: Results of several studies indicated that ischemia/reperfusion is an etiological factor in obstructive bladder dysfunction. Kohki tea pretreatment was shown to reduce the dysfunctions induced by partial outlet obstruction in rabbits. The current study was designed to determine if pretreatment of rabbits with Kohki tea could prevent the contractile dysfunctions induced by bilateral ischemia followed by reperfusion. METHODS: New Zealand white rabbits were separated into several groups; one half of each group was pretreated by oral gavage for 3 weeks with Kohki tea and the other half was treated with vehicle (water). Experimental groups were subjected to bilateral ischemia for either 1 or 3 h followed by reperfusion for either 1 h or 1 week (4 groups). The results from the experimental groups were compared to the groups of rabbits receiving sham operations. RESULTS: Under all experimental conditions, Kohki tea significantly reduced the contractile dysfunctions induced by ischemia and ischemia followed by reperfusion. CONCLUSIONS: This data is consistent with the concept that Kohki tea acts by protecting the bladder smooth muscle and mucosa from cellular damage caused by ischemia/reperfusion.

The effect of low-dose estrogen therapy on ovariectomized female rabbit bladder.

OBJECTIVES: To determine whether low-dose estrogen supplementation is as effective as high-dose supplementation in increasing bladder contractile function and mediating bladder hypertrophy and angiogenesis. METHODS: Sixteen New Zealand white female rabbits were separated into four groups of 4 rabbits each. Group 1 served as the control, and groups 2 to 4 underwent ovariectomy. The group 2 rabbits were studied 7 days after ovariectomy. The rabbits in groups 3 and 4 were medicated with 17-beta estradiol at a dose of 0.1 mg/kg/day and 1.0 mg/kg/day, respectively, for 7 days. At the end of the experiment each rabbit was anesthetized and the bladder removed for contractile, morphologic, and biochemical studies. RESULTS: Low- and high-dose estrogen administration resulted in similarly significant increases in the contractile responses to field stimulation, adenosine triphosphate, and potassium chloride. Similarly, both doses of estrogen mediated significant hypertrophy of the smooth muscle and decrease in collagen, similar levels of angiogenesis, and similar increases of citrate synthase activity. CONCLUSIONS: Low-dose estrogen produces similar physiologic, morphologic, and biochemical effects on the bladder as have been shown for high-dose estrogen.

Free radical damage as a biomarker of bladder dysfunction after partial outlet obstruction and reversal.

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

Effects of L-arginine and L-NAME on chronic partial bladder outlet obstruction in rabbit.

Nitric oxide (NO) is synthesized from L-arginine by nitric oxide synthase (NOS). NOS can be inhibited by NG-nitro-L-arginine methyl ester (L-NAME) and stimulated by supplementing the diet with L-arginine. The aim of this study was to investigate the influence of NOS activity on the response of rabbits to chronic partial bladder outlet obstruction (PBOO). Surgical PBOOs (2 and 8 wk) were performed on male New Zealand White rabbits. Before obstruction, one-third of the animals were premedicated for 7 days with L-NAME and another third with L-arginine. The results are summarized as follows. First, bladder weight after 8-wk PBOO was significantly lower in animals treated with L-arginine compared with both untreated and rabbits treated with L-NAME. Second, contractile function decreased progressively with PBOO duration. However, after 8 wk of PBOO, the L-arginine group had significantly greater contractile function compared with the no-treatment group, and the L-NAME group had significantly lower contractile function compared with the no-treatment group. Third, at 8 wk following PBOO, the level of protein oxidation and nitration was lowest for the L-arginine group and highest in the L-NAME group. These studies clearly demonstrated that increasing blood flow by stimulating NOS significantly protected the bladder from PBOO dysfunctions, whereas inhibiting blood flow by L-NAME enhanced the dysfunctions mediated by PBOO.

Effect of age on the response to short-term partial bladder outlet obstruction in the rabbit.

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

Effect of letrozole on urinary bladder function in the female rabbit.

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

Long term partial bladder outlet obstruction induced contractile dysfunction in male rabbits: a role for Rho-kinase.

AIMS: In this study we examined the expression of Rho-kinase (ROK) isoforms in rabbit detrusor smooth muscle during the progression of partial bladder outlet obstruction and correlated them with the time course of obstruction. METHODS: Detrusor samples were obtained from bladders after 1, 2, 4, and 8 weeks of obstruction and also sham operated control rabbits. Contractile responses to field stimulation (FS) and also the smooth muscle (SM) to collagen ratio were determined in isolated bladder strips. Reverse transcriptase-polymerase chain reaction, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting were used to determine the relative levels of ROK isoform expression at the mRNA and protein levels. RESULTS: Bladder weight increased gradually and contractile responses were reduced significantly over the course of obstruction. The smooth muscle/collagen ratio increased significantly during the course of obstruction. The expression of ROKalpha increased significantly to approximately the same extent in 1-4-week obstructed groups and increased further in the 8-week obstructed group, both at the mRNA and protein levels. In contrast, there was a significant decrease in the expression of ROKbeta in the obstructed groups, which gradually decrease during the course of 1-4-week obstruction period and are slightly upregulated at the decompensated stage at 8-week obstruction. CONCLUSIONS: The change in the isoforms of ROK may be part of the molecular mechanism for bladder compensation following partial bladder outlet obstruction.

Novel biomarkers of bladder decompensation after partial bladder obstruction.

AIMS: Partial bladder outlet obstruction (PBOO) results in marked contractile, biochemical, and histological alterations in the bladder. Our aim was to determine the time course of progressive PBOO in the rabbit and to find parameters that marked the shift to decompensation. MATERIALS AND METHODS: Twenty-four rabbits were subjected to 1, 2, 4, and 8 weeks of PBOO. Sham operated rabbits served as controls. At each time period, cystometry was performed and individual bladder strips were used for contractility studies. Full-thickness sections of bladder body from each rabbit were fixed in formalin and used to determine the vascular density and nerve density. The balance of the bladder body was separated between muscle and mucosa and was analyzed for superoxide dismutase (SOD) and catalase (CAT) activities. RESULTS: Bladder weight increased progressively and all contractile responses were reduced significantly over the course of obstruction. Markedly increased bladder weight and very large bladder volumes indicated decompensation. Nerve density was marked decreased in decompensated bladders. Similarly, SOD activity in muscle decreased progressively and was markedly lower in decompensated bladders. Although CAT activity of the muscle increased after 2-4 weeks of obstruction, it decreased markedly in decompensated bladders. CONCLUSION: This study shows that prolonged PBOO causes progressive deterioration in the rabbit bladder with decompensation after 8 weeks. Markedly decreased nerve density and severely reduced SOD and CAT activities are associated with the shift from compensated to decompensated function of the bladder. They may be excellent biomarkers of decompensation.

The effect of maturation and age on oestrogen-induced functional hypertrophy of the female rabbit bladder.

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

The effect of intravesical ketoprofen on acetylcholine-evoked urinary bladder contractility and detrusor overactivity in the anesthetized rabbit model.

Intraurethral procedures such as the transurethral resection of the prostate can generate detrusor overactivity and bladder irritability. The rabbit model of detrusor overactivity has proven to be an excellent model to study the effects of drugs on detrusor overactivity. Using this model, we evaluated the responses to intravesical ketoprofen. In this model, each rabbit is anesthetized and the right external carotid artery is cannulated for blood pressure monitoring. A catheter is inserted through the femoral artery and is used for administration of acetylcholine (Ach). The bladder is exposed and catheterized for bladder pressure monitoring and drug addition and the proximal urethra is ligated. Cystometry is performed, the bladder drained, and 20 ml buffer placed in the bladder. After 30 min Ach is injected proximal to the vesical artery and the response of the bladder and blood pressure is recorded. Ach administration is repeated at 10-min intervals until three consistent responses are obtained. The bladder is drained and 20 ml of ketoprofen (100 microM final concentration) is placed in the bladder. Ach injections are repeated as given above at 10 min intervals and observed for 4 h. At the end of the experiment, a second cystometry is performed. The following is a summary of the results: Ketoprofen had no effect on either micturition pressure or the intravesical volume at micturition. Ketoprofen administration resulted in a progressive 50% decrease in the response to Ach. Ketoprofen mediated a progressive decrease in detrusor overactivity amplitude and frequency, reaching a maximum at 120-180 min.

Effect of castration on male rabbit lower urinary tract tissue enzymes.

OBJECTIVES: The influence of testosterone on the prostate and corpus cavernosum have been studied extensively. However, the influence of testosterone on the lower urinary tract (bladder and urethra) have not been investigated to any great extent. The aim of this study was to determine whether androgen deprivation alters lower urinary tract metabolism. METHODS: A total of 16 rabbits were divided into four groups of four rabbits each. Each rabbit in groups 1-3 underwent surgical bilateral castration for duration of 1, 2 , and 4 weeks, and group 4 underwent sham operations. Sections of bladder body and base wall and mucosa, urethra and corpora were isolated, frozen, and stored under liquid nitrogen. The activities of citrate synthase-thapsigargin sensitive Ca(2+) ATPase (Sarco/Endoplasmic Reticulum Ca(2+ )ATPase [SERCA]), and choline acetyl-transferase were examined as markers for mitochondrial function, sarcoplasmic reticular calcium storage and release, and cholinergic nerve function, respectively. RESULTS: The activity of SR function indicator, Ca(2+) ATPase was significantly higher in the control corpora than in the control bladder or urethra. Castration resulted in decreased activity in the mitochondria specific enzyme, citrate synthase, the activity of which was greatest in the urethra and lowest in the corpora. Cholinergic nerve density indicator, choline acetyl-transferase activity was greatest in the bladder body and lowest in the urethra. CONCLUSIONS: Our data indicate that (1) significant differences exist in the activities of all three enzymes in the various organs associated with the lower urinary tract; and (2) that castration results in significant alterations in the activities of all three enzymes in the bladder body, base, urethra, and corpora.

Effect of bilateral in vivo ischemia/reperfusion on the activities of superoxide dismutase and catalase: response to a standardized grape suspension.

PURPOSE: Ischemia/reperfusion (I/R) is a major etiological factor in the bladder dysfunctions observed in men with lower tract obstruction, women with postmenopausal incontinence and with aging. A standardized grape suspension protects the rabbit urinary bladder from both the contractile dysfunctions and the morphologic changes mediated by I/R. Using a model of in vivo bilateral ischemia/reperfusion, the current study investigated the effect of this grape suspension on the endogenous antioxidant defense systems. MATERIALS AND METHODS: 24 NZW rabbits were separated into 6 groups of 4. Groups 1-3 were treated by gavage with aqueous grape suspensions; groups 4-6 received sugar-water vehicle. Groups 3 and 6 were controls. Groups 1 and 4 were subjected to bilateral ischemia for 2 h (I). Groups 2 and 5 underwent bilateral ischemia for 2 h and reperfusion for 1 week (I/R). For all rabbit bladders, the muscle and mucosa were separated by blunt dissection and analyzed separately. The effects of the various treatments on bladder antioxidant systems of cytoplasmic superoxide dismutase (Cu-Zn superoxide dismutase; SOD), and catalase (CAT) were evaluated. RESULTS: The standardized grape suspension up-regulated both SOD and CAT activity of bladder muscle and mucosa in control animals. There were few differences in the grape suspension treated animals after ischemia, and in general the activities decreased following I/R. CONCLUSIONS: Increases of SOD and CAT activity in control animals as a result of grape suspension suggest a greater antioxidant capacity. This increase in the antioxidant defense system may explain the increased protection of grape suspension in the face of ischemia and I/R. However, the activities of both enzyme systems decreased in the smooth muscle subjected to I/R showing that reperfusion damages these systems probably via oxidation damage to the enzymes themselves.

The effects of cyclical oestrogen on bladder and urethral structure and function.

OBJECTIVE: To determine the effects of cycling oestrogen in rabbits, as oestrogen is essential for physiological maintenance and integrity of the female urogenital tract. MATERIALS AND METHODS: Changes in circulating oestrogen have marked effects on the bladder of experimental animals, with ovariectomy (Ovx) inducing smooth muscle (SM) and mucosal atrophy, increasing collagen synthesis and deposition, decreasing contractile function, mucosal and SM blood flow; oestrogen reverses these effects and increases bladder mass and SM density, primarily by stimulating angiogenesis and increasing blood flow. Twenty adult female New Zealand White rabbits were divided into five equal groups; group 1 served as the control group, and groups 2-5 had a bilateral Ovx. Group 2 received no oestradiol and was assessed 2 weeks after Ovx; groups 3-5 received 17-beta oestradiol from a subcutaneous slow-release tablet 2 weeks after Ovx, which remained in place for a subsequent 2-week period. Group 3 was then assessed after the 2 weeks on oestradiol. Groups 4 and 5 then had their oestradiol tablets removed for 2 weeks and group 4 was assessed after this period off oestradiol. Group 5 then received a new oestradiol tablet that was left in place for an additional 2 weeks. RESULTS: Both groups receiving oestrogen (3 and 5) had a statistically significantly greater bladder weight than both the control group and group 2. The volume fraction of SM paralleled the bladder weight, showing that oestrogen increased the volume fraction of SM whereas Ovx and low oestrogen decreased the SM fraction. The cross-sections of the urethra from groups 3 and 5 were significantly wider than those of either the control or group 1, also being consistent with the structural effects of oestrogen. Intra-arterial phenylephrine increased urethral pressure to a similar level in all groups. The urethral pressure response to intra-arterial acetylcholine shifted from contraction in the control to relaxation in the oestrogen-treated groups. Ovx resulted in a lower vascular density, whereas oestrogen resulted in a significant increase in vascular density (angiogenesis). CONCLUSIONS: Cyclical oestrogen had pronounced structural and pharmacological effects. Low oestrogen decreased the volume fraction of SM, increased collagen, and decreased vasculature, whereas oestrogen mediated a marked hypertrophy of the SM components, decreased the collagen component, and stimulated angiogenesis. Cyclical oestrogen also had marked effects on the responses to intra-arterial acetylcholine, shifting the response from contraction to relaxation.

Role of nitric oxide in urinary bladder function: effect of L-arginine.

BACKGROUND: Evidence indicates that decreased blood flow to the bladder plays a major role in obstructive bladder dysfunction in the rabbit model of partial bladder outlet obstruction (PBOO), and that nitric oxide (NO) regulation of blood flow may be important in modulating the degree of obstructive bladder dysfunction. The specific aim of our study is to determine the effect of feeding rabbits a diet high in L-arginine on the response to PBOO. MATERIALS AND METHODS: Sixteen male NZ White rabbits were separated into 4 groups of 4 each. The rabbits in groups 1 and 3 underwent PBOO. The rabbits in groups 2 and 4 were sham-operated. For 1 week prior to surgery, and 2 weeks postoperatively, each rabbit in groups 1 and 2 was put on a diet containing 7% arginine. Rabbits in groups 3 and 4 were on a normal diet (0.76% arginine). RESULTS: PBOO resulted in a greater increase in bladder weight in the control group than the arginine group. PBOO resulted in a greater decrease in compliance in the control group than the arginine group. The contractile responses to all agents in the arginine control group were greater than in the control normal diet group. PBOO resulted in a greater decrease in the response to field stimulation in the control group than in the arginine group. CONCLUSIONS: These studies clearly demonstrate that feeding rabbits a diet high in L-arginine was beneficial for the control rabbits, and reduced the level of dysfunctions following PBOO.

Alteration of contractile and regulatory proteins in estrogen-induced hypertrophy of female rabbit bladder.

OBJECTIVES: Estrogen is essential to mediate physiologic functions in female bladders. Deficiency of estrogen has been speculated to be an etiologic factor for bladder dysfunction in postmenopausal women. Our previous studies have demonstrated that estrogen supplementation in female rabbits induces a "functional hypertrophy" of the urinary bladder smooth muscle. The present study investigated the alterations in the contractile and regulatory proteins in this model. METHODS: Twenty New Zealand white female rabbits were separated into five groups of 4 rabbits each. Group 1 served as the control, groups 2 to 6 underwent ovariectomy (Ovx), and group 2 served as the Ovx without estradiol treatment group. Two weeks after Ovx, groups 3 to 5 were given 17-beta estradiol (1 mg/kg/day) by subcutaneous implant for 1, 3, and 7 days, respectively. The expression of the contractile and regulatory proteins, such as myosin light chain kinase, rho-kinase, and caldesmon, was analyzed by Western blotting. RESULTS: The expression of myosin light chain kinase was enhanced by estradiol supplementation. The expression of rho-kinase-alpha was increased significantly (20-fold) after Ovx, which was downregulated after estrogen supplementation. No significant change was seen in rho-kinase-beta after Ovx or estradiol supplementation. The expression of caldesmon isoforms was enhanced by 1-day estradiol supplementation but decreased to lower levels than those of the control group by 3 and 7 days of estrogen treatment. CONCLUSIONS: The results of the present study have provided more understanding about the role of the contractile and regulatory proteins in detrusor muscle, in both dysfunctional atrophy induced by Ovx and functional hypertrophy induced by estrogen supplementation.

Estrogen induces angiogenesis of the female rabbit bladder.

Postmenopausal bladder dysfunction has been speculated to involve decreased circulating estrogen levels. It is our hypothesis that estrogen induces bladder dysfunctions by modulating blood flow to the bladder, i.e. low estrogen reduces blood flow to the bladder, whereas high estrogen increases blood flow. Our previous studies have demonstrated that estrogen administration in female rabbits induces a 'functional hypertrophy' of the urinary bladder smooth muscle represented by increased smooth muscle mass, which corresponds to increased contractile responses to all forms of stimulation. The present study investigates the effect of estrogen on vasculature density and distribution. Twenty-four female New Zealand white rabbits were separated into six groups of four rabbits each. Group 1 served as controls. Groups 2-6 were ovariectomized. Two weeks after ovariectomy (Ovx), groups 3-6 were given 17-beta estradiol (1 mg/kg per day) by s.c. implant for 1, 3, 7, and 14 days respectively. Blood vessel density and distribution were evaluated by immunohistochemistry and quantitative image analyses. Ovx resulted in significant vascular degeneration and decreased density, whereas estradiol administration mediated a significant angiogenic effect characterized by increased vascular density, and distribution of new vasculature within the smooth muscle bundles of the detrusor. Estradiol-induced vasculogenesis corresponds with our previously demonstrated increase in blood flow to the bladder and increased contractility. The most interesting aspect of these studies is the increased vascularization localized within the muscle bundles rather than between the muscle bundles, which may be important in the link between estrogen and increased incidence of cancers.

Effects of dextromethorphan on in vitro contractile responses of mouse and rat urinary bladders.

PURPOSE: Dextromethorphan (DXM) is a cough-suppressing ingredient in a variety of over-the-counter cough and cold medications. Dextromethorphan elevates the threshold for coughing primarily through a central mechanism. At doses recommended for treating coughs the drug is safe and effective. At much higher doses, DXM produces dissociative effects similar to those of phencyclidine and ketamine. Opioid analgesics structurally related to DXM also inhibit bladder contractions and produce urinary retention through a non-opioid mechanism. This study evaluated the direct effects of DXM on in vitro contractile responses of rat and mouse urinary bladders. METHODS: Male rats and mice were anaesthetized and their bladders removed. Bladder strips were suspended in 15 ml oxygenated Tyrode's solution containing glucose. Bladder strip contractions were evoked by field stimulation (FS), carbachol or elevated KCl concentrations and contractile responses recorded. The strips were then exposed to 3 microM (DXM) for 30 min and re-stimulated. This sequence was repeated at 10, 30, and 100 microM DXM. RESULTS: (a) The rat bladder generated significantly greater tension than the mouse bladder. (b) Dextromethorphan produced a dose-dependent inhibition of the response to FS that was approximately equal for rat and mouse bladders. FS at 8 or 32 Hz was significantly more sensitive to DXM inhibition than 2 Hz. (c) The response to carbachol was more sensitive to inhibition by DXM than the responses to FS or KCl. CONCLUSIONS: These results demonstrate that DXM inhibits bladder contractions in vitro and that mouse and rat bladders are affected to approximately the same extent.

Estrogen induced functional hypertrophy and increased force generation of the female rabbit bladder.

AIMS: Estrogen is essential for physiological maintenance of the female urogenital tract. It is believed that alterations in female sex hormones play a major role in the etiology and response to urinary tract dysfunctions. In animal studies, ovariectomy (Ovx) results in smooth muscle (SM) weakness and atrophy whereas estrogen supplementation reverses these effects. Our study seeks to establish the mechanisms by which estrogen augmentation results in increased contractility. METHODS: Twenty New Zealand White female rabbits were separated into five groups of four each. Group 1 served as control, rabbits of groups 2-5 were ovariectomized, group 2 ovariectomized received no estradiol, groups 3-5 were given 17-beta estradiol (1 mg/kg/day) by subcutaneous slow release tablet implant for 1, 3, and 7 days, respectively, beginning 2 weeks after Ovx. At the end of the experimental period, each rabbit was anesthetized and the urinary bladder was removed for contractile, histological, and biochemical studies. RESULTS: Ovx resulted in significantly decreased bladder contractile function, whereas bladders tested after estradiol administration showed increased contractility. Ovx resulted in a decrease in SM/collagen ratio, whereas estrogen resulted in an increase. The estrogen receptor (ER) density significantly increased following Ovx. After 1 day of estrogen treatment, the ER density decreased significantly below control levels, but rose progressively during the estrogen treatment. CONCLUSION: The present study demonstrates that estrogen supplementation mediates a "functional hypertrophy," that is a hypertrophy characterized by increased contractile responses to all forms of stimulation, and an increased ratio of SM/collagen.

The immediate effect of castration on female rabbit bladder blood flow and tissue oxygenation.

BACKGROUND: The female urinary bladder is a target organ for estrogen. Reductions in circulating estrogen have been associated with urothelial and vaginal atrophy and bladder disorders including incontinence and increased incidence of bladder infections. We determined the effect of short-term ovariectomy on sex hormones, bladder blood flow, and tissue oxygenation in the rabbit model. MATERIALS AND METHODS: Female New Zealand White rabbits were ovariectomized and evaluated on 1, 3, and 7 days after ovariectomy. Tissue oxygenation (pO2) and blood flow were measured with oxylab system of real time measurements. Serum estrogen and progesterone were determined at sacrifice. Tissue hypoxia was localized histologically using Hypoxyprobe-1 immunohistochemistry. RESULTS: Short-term ovariectomy caused rapid decreases in serum estrogen and progesterone, significant decreases in urothelial oxygenation and blood flow. No significant decreases in blood flow or oxygenation were noted for the detrusor smooth muscle. Immunohistochemistry confirmed the presence of urothelial hypoxia at all times after ovariectomy. Bladder muscle did not demonstrate significant levels of hypoxia. CONCLUSION: The bladder urothelium is extremely sensitive to short-term ovariectomy, with significant urothelial hypoxia seen by post-ovariectomy day 1. Urothelial hypoxia may play a significant role in pelvic pain syndromes, incontinence, and increased susceptibility to bladder infection.

Comparative effects of in vitro ischemia on contractile responses of mouse and rat bladders to various forms of stimulation.

OBJECTIVES: To compare in an in vitro study the sensitivity of rat and mouse bladders to ischemia and reperfusion. Urinary bladder dysfunction is related to ischemia and reperfusion. Several studies have been conducted in which one animal model was used in the urinary bladder dysfunction experiments, but very few studies have compared the consequences of urinary bladder dysfunction in different species. METHODS: Male rats and mice were anesthetized and their bladders removed. Bladder strips were placed in 15-mL baths containing oxygenated Tyrode's solution with glucose. Strips were stimulated by field stimulation, carbachol, and KCl, and the responses were recorded. Individual strips were switched for 1 hour to Tyrode's with no glucose equilibrated with nitrogen. During this hour, one half of the strips received repetitive stimulation. After the 1 hour of ischemia, the strips were returned to Tyrode's solution with glucose and oxygen for 1 hour without repetitive stimulation. The strips were restimulated as described above. RESULTS: The rat bladder generated significantly greater tension than the mouse bladder. The responses of the mouse, but not the rat, bladder strips were suppressed after repetitive field stimulation in normal solution. In both species, the responses were suppressed under ischemic conditions with or without repetitive stimulation. The responses of the mouse bladders were more sensitive to ischemia and repetitive stimulation than rat bladders. CONCLUSIONS: These results have demonstrated that the mouse bladder is more sensitive to ischemic stress than the rat bladder. This information would be important when choosing species for the study of ischemia and reperfusion.