Regional noradrenergic and cholinergic neurochemistry in the rat urinary bladder: effects of age

Decreased Monoamine Oxidase A Expression and Activity in the Bladders of Rats With Partial Outlet Obstruction

OBJECTIVE

To investigate changes in expression and activity of monoamine oxidase A (MAO-A) in rats with partial bladder outlet obstruction (pBOO). Previous studies suggested that monoamines, such as serotonin (5-hydroxytryptamine [5-HT]) and noradrenaline, are involved in bladder hyperactivity secondary to pBOO. However, little is known about the role of MAO-A, an enzyme oxidizing 5-hydroxytryptamine and noradrenalin, in the pathogenesis.

MATERIALS AND METHODS

Female Sprague Dawley rats were subjected to sham or pBOO operations for 7 days, then their bladders were isolated. MAO-A protein levels in the bladder were examined by Western blotting. MAO-A activity was measured by the commercially available MAO-Glo Assay kit. In addition, MAO-A distribution in the bladder was examined by immunohistochemistry.

RESULTS

Weights of the bladders from rats with pBOO were increased about 3.5-fold, compared with those from sham rats. Significant decreases in MAO-A protein and activity levels were observed in whole bladder of rats with pBOO compared with those of sham rats. By immunohistochemistry, it was firstly demonstrated that MAO-A was predominantly expressed in the detrusor layer of the sham rat bladders. The intensity of staining was decreased after pBOO operation.

CONCLUSION

We demonstrated, for the first time, the distribution of MAO-A in the bladder and the pathologic changes in MAO-A protein and activity levels in rats with pBOO. This marked decrease in MAO-A potentially resulting in increased monoamine levels, especially in the detrusor of rat bladder, might be a key factor explaining the mechanism of bladder overactivity associated with pBOO.

Accelerated onset of the vesicovesical reflex in postnatal NGF-OE mice and the role of neuropeptides

The mechanisms underlying the postnatal maturation of micturition from a somatovesical to a vesicovesical reflex are not known but may involve neuropeptides in the lower urinary tract. A transgenic mouse model with chronic urothelial overexpression (OE) of NGF exhibited increased voiding frequency, increased number of non-voiding contractions, altered morphology and hyperinnervation of the urinary bladder by peptidergic (e.g., Sub P and CGRP) nerve fibers in the adult. In early postnatal and adult NGF-OE mice we have now examined: (1) micturition onset using filter paper void assays and open-outlet, continuous fill, conscious cystometry; (2) innervation and neurochemical coding of the suburothelial plexus of the urinary bladder using immunohistochemistry and semi-quantitative image analyses; (3) neuropeptide protein and transcript expression in urinary bladder of postnatal and adult NGF-OE mice using Q-PCR and ELISAs and (4) the effects of intravesical instillation of a neurokinin (NK)-1 receptor antagonist on bladder function in postnatal and adult NGF-OE mice using conscious cystometry. Postnatal NGF-OE mice exhibit age-dependent (R²=0.996-0.998; p≤0.01) increases in Sub and CGRP expression in the urothelium and significantly (p≤0.01) increased peptidergic hyperinnervation of the suburothelial nerve plexus. By as early as P7, NGF-OE mice exhibit a vesicovesical reflex in response to intravesical instillation of saline whereas littermate WT mice require perigenital stimulation to elicit a micturition reflex until P13 when vesicovesical reflexes are first observed. Intravesical instillation of a NK-1 receptor antagonist, netupitant (0.1μg/ml), significantly (p≤0.01) increased void volume and the interval between micturition events with no effects on bladder pressure (baseline, threshold, peak) in postnatal NGF-OE mice; effects on WT mice were few. NGF-induced pleiotropic effects on neuropeptide (e.g., Sub P) expression in the urinary bladder contribute to the maturation of the micturition reflex and are excitatory to the micturition reflex in postnatal NGF-OE mice. These studies provide insight into the mechanisms that contribute to the postnatal development of the micturition reflex.

Postnatal expression of corticotropin releasing factor (CRF) in rat urinary bladder

Corticotropin releasing factor (CRF) is a neuropeptide expressed in micturition reflex circuitry and different roles in these reflexes have been suggested. These studies examined the expression of CRF/CRF receptors in the urinary bladder during postnatal development in the rat. Urinary bladder was harvested from rats (postnatal (P) day 0-adult) euthanized by isoflurane (4%) and thoracotomy. CRF protein expression significantly (p<or=0.01) decreased in the urothelium with increasing postnatal age. In contrast, CRF-immunoreactivity (IR) was increased in nerve fibers in the suburothelial plexus during the second-third postnatal week. Total CRF protein from urinary bladder significantly increased during the second-third postnatal weeks as determined with ELISAs. CRF receptor 2 (CRFR(2)) transcript was expressed in urinary bladder of all postnatal ages examined whereas no CRFR(1) transcript was expressed at any postnatal age examined. We also demonstrated changes in urinary bladder mRNA expression for the neuropeptides, galanin, substance P, vasoactive intestinal polypeptide and pituitary adenylate cyclase activating polypeptide during postnatal development. These studies demonstrate changes in the CRF expression in urinary bladder, specifically in the urothelium and nerve fibers of the suburothelial plexus during postnatal development. Changes in CRF expression and neuropeptide expression in general in the urinary bladder may contribute to the emergence of mature voiding reflexes.

Increased alpha1-adrenergic activity in the rat bladder by depletion of ovarian hormones

PURPOSE

It is possible that postmenopausal loss of ovarian hormones leads to sensitization and/or over expression of alpha1-adrenergic receptors. The objective of this study was to determine whether ovariectomy enhances efferent transmission and, hence, increases contractility in the rat bladder by increasing alpha1-adrenergic receptors.

MATERIALS AND METHODS

This hypothesis was tested in 4 urethane anesthetized groups of female rats, including regularly cycling rats in metestrus and proestrus, and rats 4 months after ovariectomy with and without estradiol replacement, respectively. The bladder was catheterized through the urethra to measure intravesical pressure. The left femoral artery was also catheterized for local delivery of the nonspecific alpha1-adrenergic agonist phenylephrine, the alpha1-adrenergic antagonist prazosin, the specific alpha1A antagonist 5-methylurapidil or dimethyl sulfoxide (Sigma) in saline vehicle. In some rats bladder contractility was assessed by cystometry, followed by treatment with phenylephrine injected via the femoral artery. In other rats the bladder was denervated and a platinum electrode was wrapped around branches of the left pelvic nerve for electrical stimulation. The amplitude of micturition contractions and contractions evoked by phenylephrine or pelvic nerve stimulation was measured.

RESULTS

Micturition and phenylephrine evoked bladder contractions were significantly increased in ovariectomized rats without estradiol replacement. Prazosin significantly decreased contractions evoked by pelvic stimulation in a dose dependent manner. This decrease was significantly larger in ovariectomized rats without estradiol replacement compared to that in the other groups. The inhibition of stimulation evoked contractions by 5-methylurapidil was also greater in ovariectomized rats without estradiol replacement than in rats with estradiol replacement.

CONCLUSIONS

Results suggest that the depletion of ovarian hormones after ovariectomy enhances alpha1-adrenergic activity.

Effect of Melatonin on Age Associated Changes in Guinea Pig Bladder Function

PURPOSE

The incidence of urinary incontinence increases with age but the cause and effect relationship between aging and altered bladder function is poorly understood. It was suggested that melatonin can ameliorate negative effects induced by aging by its free radical scavenging activity and its ability to decrease oxidative stress. We investigated the changes in bladder function evoked by aging and the possible benefits of melatonin treatment on age related bladder disturbances.

MATERIALS AND METHODS

Bladder function was assessed using cystometry in conscious, freely moving female guinea pigs. Animals were grouped according to age as young adults (4 months old) and senescents (18 to 20 months old). A group of senescent animals were treated with 2.5 mg kg(-1) day(-1) melatonin for 21 days.

RESULTS

Aging led to increased detrusor activity, as demonstrated by short micturition intervals, decreased bladder capacity and spontaneous contractions during the filling phase. During the voiding phase aged animals showed lower micturition pressures than young adults. Melatonin counteracted the cystometric changes in senescent animals and restored micturition parameters to those of young adults.

CONCLUSIONS

These results show that in guinea pigs aging induces detrusor overactivity. Melatonin treatment improved age induced changes in bladder function. If similar effects can be demonstrated in humans, melatonin treatment may be a new approach to decrease the impact of age related bladder disorders.

P2X2 and P2X3 receptor expression in postnatal and adult rat urinary bladder and lumbosacral spinal cord

P2X receptors mediate the effects of ATP in micturition and nociception. During postnatal maturation, a spinobulbospinal reflex and voluntary voiding replace primitive voiding reflexes. This may involve changes in neuroactive compounds and receptors in bladder reflex pathways. We examined P2X2 and P2X3 receptors in bladder and spinal cord from postnatal (P0-P36, indicating number of days) and adult Wistar rats. Western blot of whole bladders for P2X2 and P2X3 expression was performed. Immunostaining for P2X2 and P2X3 receptors in urothelium and detrusor smooth muscle whole mounts and spinal cord sections was examined. Western blot demonstrated an age-dependent decrease (R(2) = 0.96, P Collapse

Key Words

• postnatal development
• micturition reflexes
• sacral parasympathetic nucleus
• dorsal commissure
• dorsal horn

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MESH Headings

• Aging/metabolism
• Animals
• Female
• Lumbosacral Region
• Male
• Rats
• Rats, Wistar
• Receptors, Purinergic P2/metabolism
• Receptors, Purinergic P2X2
• Receptors, Purinergic P2X3
• Spinal Cord/metabolism
• Tissue Distribution
• Urinary Bladder/metabolism

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Grants

• DK-060481 NIDDK NIH HHS
• NS-040796 NINDS NIH HHS
• R01 DK065989 NIDDK NIH HHS
• R56 DK060481 NIDDK NIH HHS
• R29 DK051369 NIDDK NIH HHS
• DK-065989 NIDDK NIH HHS
• R01 DK060481 NIDDK NIH HHS
• R01 NS040796 NINDS NIH HHS
• DK-051369 NIDDK NIH HHS
• R01 DK051369 NIDDK NIH HHS

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Affiliation(s)

Simon Studeny Department of Neurology, Anatomy and
Ali Torabi Department of Neurology, Anatomy and
Margaret A. Vizzard Department of Neurology, Anatomy and Neurobiology, University of Vermont, College of Medicine, Burlington, Vermont, VT 05405

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Distribution and fate of cocaine- and amphetamine-regulated transcript peptide (CARTp)-expressing cells in rat urinary bladder: a developmental study

We examined the distribution and fate of cocaine- and amphetamine-regulated transcript peptide (CARTp)(55-102)-immunoreactive (IR) structures in the neonatal and adult rat urinary bladder. Double-labeling studies examining CARTp with tyrosine hydroxylase (TH), neuronal nitric oxide synthase (nNOS), or choline acetyltransferase (ChAT) were performed in wholemounts of urothelium or detrusor or cryostat sections of the bladder. In younger animals (postnatal day [P]1, P3), CARTp-IR cell bodies in detrusor smooth muscle were observed in large clusters ( approximately 100 cells/cluster) at the ureteral insertion and along thick bundles of nerve fibers at the bladder base. The total number of CARTp-IR cells was significantly reduced (by five-fold) at P14, and this reduced number persisted into adulthood. The decrease in the number of CARTp-expressing cells was complemented with positive staining for cleaved caspase-3, suggesting that apoptosis contributed to this decrease. At birth (P1), all CARTp-IR cells expressed the neuronal marker Hu. After birth, CARTp was expressed by some neurons (CARTp-IR, Hu-IR) that represent intramural ganglion cells and by cells that lacked a neuronal phenotype (CARTp-IR, Hu-) but did express TH. Neither of these cell populations expressed ChAT immunoreactivity in adult bladder. These cells (CARTp-IR, Hu-, TH-IR) may represent paraganglion or small intensely fluorescent (SIF) cells. The percentage of colocalization of CARTp-IR and nNOS or TH was dependent on postnatal age and showed an inverse relationship. At P1, 67.1 % of CARTp-IR cells expressed nNOS immunoreactivity. Decreased colocalization was observed with increasing postnatal age. In contrast, 19.5% of CARTp-IR cells expressed TH at P1, but colocalization increased with postnatal age. The suburothelial plexus lacked CARTp-IR nerve fibers until P14, when nerve fibers with varicosities were observed in the urethra and bladder neck region. In summary, we demonstrate 1) a decrease in the number of CARTp-IR cells in rat detrusor in early postnatal development; 2) apoptotic events in the bladder during early postnatal development; 3) rostral migration of CARTp-IR cells from the ureteral insertion toward the bladder body during postnatal development; 4) the presence of different populations of CARTp-IR cells, some with and others without a neuronal phenotype; and (5) age-dependent changes in chemical coding of CARTp-IR cells with postnatal development. This study demonstrates that CARTp-IR intramural ganglia and CARTp-IR paraganglion or SIF cells exist in the postnatal and adult rat bladder, although the role of these cell types remains to be determined.

Corticotropin-releasing factor (CRF) expression in postnatal and adult rat sacral parasympathetic nucleus (SPN)

The neural control of micturition undergoes marked changes during the early postnatal development. During the first few postnatal weeks, the spinal micturition reflex is gradually replaced by a spinobulbospinal reflex pathway that is responsible for micturition in adult animals. Upregulation of brainstem regulation of spinal micturition pathways may contribute to development of mature voiding patterns. We examined the expression of corticotropin-releasing factor (CRF), present in descending projections from Barrington's nucleus to the sacral parasympathetic nucleus (SPN), in postnatal (P0-P36) and adult Wistar rats (P60-90). CRF-immunoreactivity (IR) was present predominantly in the SPN region, although some staining was also observed in the dorsal horn and dorsal commissure in L5-S1 spinal segments. CRF-IR in spinal cord regions was age dependent (R2=0.87-0.98). The majority of the CRF-IR in the lumbosacral spinal cord was eliminated by complete spinalization (2-3 weeks). Double-label immunohistochemistry was combined with quantitative confocal laser scanning microscopy to quantify the number and percentage of colocalization between CRF-immunoreactive varicosities and preganglionic somas or proximal neurites in the SPN in postnatal and adult rats. Results demonstrate an age-dependent upregulation of CRF-IR in the SPN region and specifically in association with preganglionic parasympathetic neurons identified with neuronal nitric oxide synthase (nNOS)-IR. CRF-immunoreactive varicosities on or within a 1 microm perimeter of nNOS-immunoreactive somas or proximal neurites also increased with postnatal age. The upregulation of CRF-IR in bulbospinal projections to the SPN may contribute to mature voiding reflexes.

Management of detrusor dysfunction in the elderly: changes in acetylcholine and adenosine triphosphate release during aging

Numerous studies have detailed age-related changes in the structure and function of the bladder that may contribute to the high prevalence of overactive bladder (OAB) in the elderly population, but the relation of these changes to OAB symptoms remains unclear. Physiologic and neurochemical studies have been conducted in human detrusor strips obtained from people of different ages, focusing on potential changes in cholinergic and purinergic neurotransmission, as well as the release and actions of acetylcholine (ACh) from nonneuronal bladder cells. Results from physiologic and microdialysis experiments indicate that purinergic transmission increases with age, whereas cholinergic transmission decreases. These effects are most likely because of decreased release of ACh and increased release of adenosine triphosphate (ATP) from postganglionic parasympathetic axons innervating the bladder. Immunohistochemical experiments showed that choline acetyltransferase in the human detrusor is contained not only in parasympathetic axons, but also in cells of the urothelium. The release of nonneuronal ACh increases with age and detrusor stretch. The age-related increase in purinergic transmission in the detrusor and other data indicating that responses to ATP are increased in detrusor overactivity suggest that purinergic receptor antagonists may provide a useful complement to muscarinic receptor antagonists in the treatment of older patients with OAB. Nonneuronal ACh release may play a key role in the storage phase of the micturition reflex, and this may explain, at least in part, the effectiveness of antimuscarinic agents for the treatment of OAB.

Increased adrenergic contractility and decreased mRNA expression of NOS III in aging rat urinary bladders

Our objective was to study age-related changes in adrenergic contractility and gene expression profile in the rat urinary bladder. Young (3-month old), adult (10-month old) and senescent (30-month old) male WAG/Rij rats were used. Gene expression profile in the rat urinary bladder was defined using Atlas microarray technology. In vitro contractile responses induced by KCl, phenylephrine (PHE) and norepinephrine (NE) were compared in isolated urinary bladders dissected from young, adult and senescent rats. Among a total of 1176 genes present on the arrays, 15 genes showed an increase in expression and 10 genes a decrease with age. Four genes related to nerve growth factor were upregulated whereas NOS type III was downregulated in aging rats. Intrinsic contractility of isolated rat urinary bladders was not changed between adult and aging rats as judged by the response curves to KCl. In contrast, an age-related increase in the maximal contractile responses to NE, but not PHE, was noticed (13 +/- 1, 48 +/- 2% and 59 +/- 2% at 3, 10 and 30 months, respectively). The alpha1D-adrenoceptor antagonist BMY7378 antagonized NE-induced contractions with low potency in both groups suggesting the involvement of the alpha1A-adrenoceptor subtype. This was confirmed by microarray, which demonstrated mRNA expression for the alpha1A-adrenoceptor subtype only. These results suggest that aging of the urinary bladder is associated with an increase in the maximal contractile response to NE which could be due to NO shortage resulting from downregulation of urothelial NOS III.

Functional and morphological modifications of the urinary bladder in aging female rats

In female Wistar/Rij rats, 10 and 30 mo old, the micturition profiles in conscious animals, the contractile responses of the isolated urinary bladder, and the histology of the vesical tissue have been investigated. During cystomanometry, 60% of conscious senescent rats, but only 25% of young adult rats, showed spontaneous contractions during the bladder-filling phase. In aging rats, micturition pressure and duration of micturition were significantly higher by approximately 40-50%. In contrast, bladder capacity, bladder compliance, micturition volume, and residual volume were not modified with age. In vitro, the contractile responses of the bladder body to KCl, carbachol, arecoline, and alpha,beta-MeATP were similar in tissues from young adult and senescent rats. In contrast, maximum responses to noradrenaline, but not phenylephrine, were two times greater in the older rats. Isoprenaline exhibited the same potency in relaxing KCl-precontracted bladder body of 10- and 30-mo-old animals. Morphometric analysis showed a significant increase in the mean thickness of the muscularis layer with age, whereas the collagen density significantly decreased in the muscularis and in the lamina propria layers. The fact that the majority of senescent rats displayed bladder instability and increased response to alpha-adrenergic agonists suggests that this strain of rat seems a good model for the aged human. However, other characteristics of the aging human urinary tract (urinary frequency, decreased cystometric capacity, and decreased detrusor contractility associated with fibrosis) are not present.

Developmental expression of urinary bladder neurotrophic factor mRNA and protein in the neonatal rat

These studies were performed to determine the developmental expression pattern of neurotrophic factor (NTF: nerve growth factor (betaNGF), brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), ciliary neurotrophic factor (CNTF), neurotrophin-3 (NT-3) and NT-4 mRNA and NGF, NT-3 and NT-4 protein in the urinary bladder of the postnatal Wistar rat. It was hypothesized that NTFs may contribute to the development of the spinobulbospinal micturition reflex that represents the adult micturition pattern. Changes in NTF mRNA or protein expression in the urinary bladder at the time of development of the mature micturition reflex (postnatal days (P) 16-18) may suggest an involvement of target-derived NTFs in this maturation process. Developmental ages, prior to (P5, P10, P15) or following (P20, P30, adult P90) the development of the spinobulbospinal micturition reflex were selected and the urinary bladder was analyzed for levels of neurotrophic factor mRNA or protein. Results from ribonuclease protection assays demonstrated a similar developmental pattern among each neurotrophic factor examined. Neurotrophic factor mRNA levels increased by P10 and reach a maximum by P15. Subsequently, NTF mRNA levels declined to adult levels that were less than the earliest postnatal time examined (P5). NTF mRNA expression was significantly (p</=0.05-0.001) greater at P10, P15, P20 and P40 (NT-4 mRNA) compared to adult levels for each NTF examined except GDNF mRNA. In general, NGF, NT-3 and NT-4 urinary bladder protein levels in early postnatal development, as determined by ELISA, were similar when compared to the corresponding mRNA expression. Differences in the correlation between NT-3 and NT-4 mRNA and protein expression were demonstrated in the adult urinary bladder where significantly (p</=0. 001) greater levels of protein were revealed despite relatively low abundance of NT-3 and NT-4 mRNA. The developmental expression pattern (maximum expression at the second to third postnatal week) of NTFs in the urinary bladder is consistent with a potential role in the development of the spinobulbospinal reflex. Relatively high expression of NT-3 and NT-4 protein in the adult urinary bladder suggests a potential importance of these factors in the adult lower urinary tract.

Rat: overview and innervation

Despite the development of molecular and cellular methods for examining physiological processes, the use of the whole animal model remains essential to advance knowledge regarding the integration and coordination of events associated with urinary tract function. The rat offers an inexpensive and versatile species to investigate bladder and urethral responses to drugs or pathology. Models for many disorders have been developed in rodents including diabetes, multiple sclerosis, spinal cord injury, Parkinson's disease, bladder outlet obstruction, pain, and aging. This review examines methodologies to evaluate lower urinary tract function and manipulations used to create pathological models in rodents.

Analysis of regional norepinephrine content in the rabbit bladder after acute electrical pelvic floor stimulation

Experiments were carried out to evaluate the regional norepinephrine (NE) content of the rabbit bladder after acute electrical pelvic floor stimulation (EPFS). After 30 minutes of EPFS, the content of NE increased significantly in both the bladder base and body (p < 0.05). Furthermore, this increased NE content continued for 1 to 2 hours after cessation of stimulation. The content of NE in the bladder base and body in rabbits treated with alpha-methyl-paratyrosine (AMT) was lower than in the control group. Application of EPFS increased NE content in the bladder even in animals pretreated with AMT. Based on these findings, during EPFS the hypogastric nerve would be presumed to play a significant role in bladder inhibition. Increased synthesis of NE probably did not play an important role in elevation of NE content after EPFS.

The alterations of norepinephrine and acetylcholine concentrations in immature rat urinary bladder caused by streptozotocin-induced diabetes

The concentrations of norepinephrine (NE) and acetylcholine (ACh) in the body and base of the bladder were investigated two, four and eight weeks after the administration of streptozotocin to four-week-old rats. At four and eight weeks after following dosage, NE concentrations in the base of the bladder of the diabetic rats were significantly higher than those of control rats. At the two-week diabetic condition, ACh concentrations in both the body and base of the bladder diabetic rats were about two-fold higher than in the respective control levels and remained constant for eight weeks. However, the control rats showed dramatic increase in ACh concentration from two to four weeks after dosage. There was no significant difference in the response of bladder muscle strips to phenylephrine, isoproterenol and ACh in the diabetic vs. control rats throughout the experiment. These observations suggest that the alteration of autonomic nervous system may occur at an early stage of diabetes mellitus in immature rats and that the high concentration of NE in the diabetic bladder base may reflect an adaptive overfunction of the adrenergic system probably to maintain continence. Furthermore, the lack of change in ACh concentration with age in diabetic rats may suggest an impaired development of the cholinergic system.

Effects of age and streptozotocin-induced diabetes on contents and effects of substance P and vasoactive intestinal polypeptide in the lower urinary tract of the rat

The urinary bladder and urethral content of substance P and vasoactive intestinal polypeptide and the in vitro effects of the peptides on the bladder were studied at 6 weeks and 6 months of streptozotocin-induced diabetes in the rat. The results were compared with those obtained in age-matched control animals. Both short-term and long-term streptozotocin treatment induced a clearcut increase in bladder weight. Bladder substance P content was increased in both groups of diabetic animals but substance P concentration was similar in control and diabetic animals. Vasoactive intestinal polypeptide content was slightly higher in diabetic animals than in controls but vasoactive intestinal polypeptide concentration was significantly lower in the bladders from both short-term and long-term diabetic animals. The bladder contractile response to substance P was similar in all groups of animals and vasoactive intestinal polypeptide was found to be devoid of contractile or relaxatory effects in the rat bladder. No change in urethral weight was seen with diabetes. There were no clear-cut changes in the urethral contents or concentrations of substance P and vasoactive intestinal polypeptide. The study also enabled comparisons between younger (3 months) and older (9 months) rats. This comparison showed a decrease in the concentrations and contents of substance P and vasoactive intestinal polypeptide between young and older rats. The changes were seen in both the bladder and the urethra and were similar in diabetic and normal animals.

A method to study drug concentration-depth profiles in tissues: mitomycin C in dog bladder wall

Determination of the depth of penetration of locally applied drug therapy and evaluation of possible mechanisms of drug transport require knowledge of drug concentration-versus-tissues depth profiles. A method to determine the drug concentration-depth profile is needed. We have devised such a method and used it to determine the penetration of mitomycin C (MMC) in the dog bladder wall after intravesical drug instillation. This method is based on sectioning of frozen tissue into 40-microns segments, followed by drug extraction and high-pressure liquid chromatography analysis. Tissue concentrations could be detected with a sensitivity of 1 ng/sample, or 20 ng/g for tissue samples of approximately 2 x 2 cm. This sensitivity was sufficient to describe the penetration of MMC in the bladder wall of dogs, using an identical instillation technique, dwell time, and MMC concentration as in human patients. Tissue concentrations were expressed relative to tissue weight or tissue protein contents. For MMC, standardization to tissue weight yielded a better mathematical fit of the concentration-versus-depth profiles than standardization to protein content. The time interval between tissue harvesting and freezing was critical. The MMC concentration at the urothelial side of dog bladders was 2- to 10-fold higher in samples processed immediately after harvesting, compared to samples processed after 1 hr or longer. This significant decrease was not due to drug metabolism in situ. In separate in vitro experiments, we found that the degradation of MMC in 8% tissue homogenate was relatively slow, with only a 30% decline in concentration over 24 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Bladder function in rats with short- and long-term diabetes; effects of age and muscarinic blockade

The development of alterations in urinary bladder function was studied in rats during six months of streptozotocin-induced diabetes. The results were compared with those obtained in age-matched controls. The bladders from the control rats developed with increasing age an increased micturition volume, a decreased micturition interval, and increased bladder compliance and capacity despite an unaltered bladder weight and unaltered passive and active length-tension relations. The effects of muscarinic blockade were somewhat more pronounced in the older control rats. Following streptozotocin 24 hour diuresis increased rapidly to stabilize within two weeks at a level 15 times higher than the original. This was accomplished initially by an increase in the micturition frequency and then gradually by an increased micturition volume. After six weeks bladder weight had increased more than twofold and did not increase further with time. Despite this both micturition volume and bladder capacity increased from six weeks to six months of diabetes. The diabetic bladders had at low frequencies of stimulation a higher resistance to scopolamine than their age-matched controls. At higher frequencies the resistance to muscarinic blockade showed a similar decrease with age as for the controls. The more pronounced decrease in micturition pressure following atropine treatment in six weeks diabetic rats thus suggests an increased excitation frequency during micturition. No supersensitivity to carbachol was found even after six months of diabetes.