Rat Urinary Bladder Research Articles

Dose dependency of γ-H2AX formation in the rat urinary bladder treated with genotoxic and nongenotoxic bladder carcinogens.

We previously reported that immunostaining for γ-H2AX, a biomarker of DNA damage, in the rat urinary bladder is useful for early detection of bladder carcinogens in 28-day toxicity studies. Here, we aimed to examine the dose dependency of γ-H2AX formation in the urinary bladder of rats. Male F344 rats (aged 6 weeks) were orally administered N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN; 0%, 0.0001%, 0.001%, 0.01%, 0.02%, or 0.05% in drinking water), a genotoxic bladder carcinogen, and melamine (0%, 0.3%, 1.0%, or 3.0% in the diet), a nongenotoxic bladder carcinogen, for 2 days or 4 weeks. Immunohistochemical analysis showed that γ-H2AX- and Ki67-positive epithelial cells in the bladder urothelium were significantly increased, with a clear dose dependency, in both BBN- and melamine-treated groups. Additionally, γ-H2AX formation was detected from the lower-dose group, without increased Ki67 expression or histopathologic findings. The ratios of γ-H2AX-positive cells at week 4 in both BBN- and melamine-treated groups were higher than those on day 2, indicating the time-dependent increase in γ-H2AX formation. Immunofluorescence double-staining revealed that γ-H2AX single-positive cells without Ki67 expression were often found in the urothelium of BBN-treated rats, whereas most γ-H2AX-positive cells were Ki67-positive in the melamine group. Our results demonstrated that γ-H2AX formation in the urinary bladder increased in a clear dose-dependent manner and that γ-H2AX immunostaining has the potential to detect bladder carcinogens after a 2-day administration. Furthermore, the association of genotoxic mechanisms in bladder carcinogenesis could be determined by analyzing the colocalization of γ-H2AX and Ki67 in the urothelium.

β3 Adrenoceptor-induced cholinergic inhibition in human and rat urinary bladders involves the exchange protein directly activated by cyclic AMP 1 favoring adenosine release.

The mechanism by which β3 receptor agonists (e.g. mirabegron) control bladder overactivity may involve adenosine release from human and rat detrusor smooth muscle. Retrograde activation of adenosine A1 receptors reduces ACh release from cholinergic bladder nerves. β3 -Adrenoceptors usually couple to adenylyl cyclase. Here we investigated, which of the cAMP targets, protein kinase A or the exchange protein directly activated by cAMP (EPAC) could be involved in this cholinergic inhibition of the bladder. [3 H]ACh and adenosine release from urothelium-denuded detrusor strips of cadaveric human organ donors and rats were measured by liquid scintillation spectrometry and HPLC, respectively. In vivo cystometry was also performed in urethane-anaesthetized rats. The exchange protein directly activated by cAMP (EPAC) inhibitor, ESI-09, prevented mirabegron- and isoprenaline-induced adenosine release from human and rat detrusor strips respectively. ESI-09, but not the PKA inhibitor, H-89, attenuated inhibition of [3 H]ACh release from stimulated (10 Hz) detrusor strips caused by activating β3 -adrenoceptors, AC (forskolin) and EPAC1 (8-CTP-2Me-cAMP). Isoprenaline-induced inhibition of [3 H]ACh release was also prevented by inhibitors of PKC (chelerythrine and Go6976) and of the equilibrative nucleoside transporter 1 (ENT1; dipyridamole and NBTI), but not by PLC inhibition with U73122. Pretreatment with ESI-09, but not with H-89, prevented the reduction of the voiding frequency caused by isoprenaline and forskolin in vivo. Data suggest that β3 -adrenoceptor-induced inhibition of cholinergic neurotransmission in human and rat urinary bladders involves activation of an EPAC1/PKC pathway downstream cAMP production resulting in adenosine outflow via ENT1.

Cotinine, a major nicotine metabolite, induces cell proliferation on urothelium in vitro and in vivo

Tobacco smoking is a major risk factor for human cancers including urinary bladder carcinoma. In a previous study, nicotine enhanced rat urinary bladder carcinogenesis using a rat urinary bladder two-stage carcinogenesis model. In the present study, nicotine metabolites (cotinine, trans-3’-hydroxy cotinine and N’-nitrosonornicotine) were evaluated in a cell proliferation assay using urinary bladder urothelial cell lines. Cotinine (0.1 to 1 mM) induced the highest cell proliferation compared to the others, including nicotine, in three bladder cancer cell lines (RT4, T24 and UMUC3 cells). By Western blot, cotinine induced phosphorylation of Stat3 and expression of cyclin D1 in UMUC3 cells. The cell proliferation induced by cotinine was blocked by inhibitors of nicotinic receptors (10 nM SR16584 or 10 μM methyllycaconitine citrate) and Stat3 (100 nM stattic). In an in vivo study, cotinine (13, 40 and 120 ppm) in drinking water also induced cell proliferation and simple hyperplasia in urinary bladder and renal pelvis urothelium of rats, but to a lesser degree compared to nicotine (40 ppm). Cytotoxicity detected by scanning electron microscopy and apoptosis in the bladder urothelium were induced by nicotine but not cotinine. These data suggest that cotinine is able to induce urothelial cell proliferation both in vitro and in vivo, and high urinary concentrations may enhance urothelial carcinogenesis.

Long-term diabetes causes molecular alterations related to fibrosis and apoptosis in rat urinary bladder

Diabetes induces time-dependent alterations in urinary bladders. Long-term diabetes causes an underactive bladder. However, the fundamental mechanisms are still elusive. This study aimed to examine the histological changes and the potential molecular pathways affected by long-term diabetes in the rat bladder. Diabetes was induced in 8-week-old male Lewis rats by streptozotocin, while age-matched control rats received citrate buffer only. Forty-four weeks after diabetes induction, bladders were harvested for histological and molecular analyses. The expressions of proteins related to fibrosis, apoptosis and oxidative stress as well as the cellular signaling pathway in the bladder were examined by immunoblotting. Histological examinations illustrated diabetes caused detrusor hypertrophy and fibrotic changes in the bladder. Immunoblotting analysis demonstrated higher collagen I but lower elastin expression in the bladder in diabetic rats. These were accompanied by an increase in the expression of transforming growth factor-beta1, along with the downregulation of matrix metalloptoteinase-1, and upregulation of tissue inhibitor of metalloproteinase-1. Diabetic rats showed an increase in nitrotyrosine, but decrease in nuclear factor erythroid-related factor 2 (Nrf2) levels in the bladder. Enhanced apoptotic signaling was observed, characterized by increased expression of Bcl-2-associated X protein (Bax), decreased expression of Bcl-2, in the diabetic bladder. The nerve growth factor level was decreased in the diabetic bladder. A significant suppression in the protein expressions of phosphorylated extracellular signal-regulated kinases 1/2 was found in diabetic bladders. This study demonstrated that long-term diabetes caused molecular changes that could promote fibrosis and apoptosis in the bladder. Oxidative stress may be involved in this context.

Lamina propria: The connective tissue of rat urinary bladder mucosa.

To describe and illustrate the structure of the propria, the bladder of adult rats was fixed in controlled conditions of distension and examined by light and electron microscopy. The lamina propria, ~50 µm thick in the distended bladder, consists of a superficial part (the cellular component), adjacent to the urothelium, rich in nerves, capillaries, fibroblasts and thin bundles of collagen, and a deep, thicker part (the fibrous component), adjacent to the detrusor, rich in large collagen fibres and with few fibroblasts. In the cellular part there is an extensive plexus of afferent nerve fibers and a dense capillary network (with numerous pericytes), lying close to the urothelium, that is unique to the bladder. The main resident cells are fibroblasts, adhering to each other at the end of laminar extensions without forming specialized junctions. The deep part of the lamina propria is made of thick collagen fibers, interwoven and crisscrossing each other, with a few fibroblasts in the interstitial spaces between them. In summary, the superficial part of the lamina propria has most of the bladder afferent nerves, contains many fibroblasts and has a network of suburothelial capillaries. The deep part as a whole forms an ovoid balloon of woven fibrous material that is acted upon by the detrusor musculature attached to its outer surface. The lamina propria is a strong fibrous barrier between urothelium and musculature. The abundance of collagen points to the main role for its fibroblasts, that is, the production of collagen fibrils, assisting the mechanical role of the lamina propria.

Evaluation of Antispasmodic Effect of Arcapillin on Smooth Muscles of Rats

Background: Arcapillin, 2',4',5-trihydroxy-5',6,7–trimethoxyflavone, is a flavone aglycone isolated from several Artemisia species, though, it was first identified from A. capillaris. The Artemisia species are used in folk medicine as a remedy for gastrointestinal and liver illnesses, hypertension, fever and inflammation. Studies indicated a potential role of arcapillin to relieve symptoms of liver disorders; however, there is no report yet in the literature of its effect on smooth muscles. Objective: Our study aims to evaluate the effect of arcapillin, isolated from A. monosperma, on the contractile activity of rat smooth muscles. Materials and Methods: Increased concentrations of arcapillin were tested on isolated rat ileum, pulmonary artery, trachea, and urinary bladder. The muscle contraction was recorded upon addition of arcapillin in eight cumulative concentrations of half log units in the range of [10-7 M -3×10-4 M]. Depending on the organ-containing muscles, the preparations were treated with arcapillin either at basal tonus or after pre-stimulated via a contractile agent; 10-3 M O-acetylcholine on ileum and 10-5 M L-phenylephrine on pulmonary artery rings. Control tissues were treated with sodium hydroxide in an equivalent concentration to that used to dissolve the flavone. Results: Arcapillin caused a dose-dependent relaxation on ileum preparation and pulmonary artery. The inhibition of the contractile activity of ileum was reversible within 60 seconds after washing off the flavone. The urinary bladder showed a slight increase in contraction at the highest concentrations starting at [10-4 M] of arcapillin. There was no observed effect on the contraction of tracheal smooth muscles by all tested concentrations of arcapillin. Conclusion: The antispasmodic activity of arcapillin may contribute to the pharmaceutical importance of A. monosperma in particularly to treat gastrointestinal disorders.

Dystrophin is expressed in smooth muscle and afferent nerve fibers in the rat urinary bladder.

ABSTRACTIntroductionWith increasing life expectancy, comorbidities become overt in Duchenne muscular dystrophy (DMD). Although micturition problems are common, bladder function is poorly understood in DMD. We studied dystrophin expression and multiple isoform involvement in the bladder during maturation to gain insights into their roles in micturition.MethodsDystrophin distribution was evaluated in rat bladders by immunohistochemical colocalization with smooth muscle, interstitial, urothelial, and neuronal markers. Protein levels of Dp140, Dp71, and smooth muscle were quantitated by Western blotting of neonatal to adult rat bladders.ResultsDystrophin colocalized with smooth muscle cells and afferent nerve fibers. Dp71 was expressed two‐ to threefold higher compared with Dp140, independently of age. Age‐related muscle mass changes did not influence isoform expression levels.DiscussionDystrophin is expressed in smooth muscle cells and afferent nerve fibers in the urinary bladder, which underscores that micturition problems in DMD may have not solely a myogenic but also a neurogenic origin. Muscle Nerve 60: 202–210, 2019

Noradrenaline-Induced Relaxation of Urinary Bladder Smooth Muscle Is Primarily Triggered through the β3-Adrenoceptor in Rats.

β-Adrenoceptors are subclassified into 3 subtypes (β1-β3). Among these, β3-adrenoceptors are present in various types of smooth muscle and are believed to play a role in relaxation responses of these muscles. β3-Adrenoceptors are also present in urinary bladder smooth muscle (UBSM), although their expression varies depending on the animal species. To date, there has been little information available about the endogenous ligand that stimulates β3-adrenoceptors to produce relaxation responses in UBSM. In this study, to determine whether noradrenaline is a ligand of UBSM β3-adrenoceptors, noradrenaline-induced relaxation was analyzed pharmacologically using rat UBSM. We also assessed whether noradrenaline metabolites were ligands in UBSM. In isolated rat urinary bladder tissues, mRNAs for β1-, β2-, and β3-adrenoceptors were detected using RT-PCR. In UBSM preparations contracted with methacholine (3 × 10-5 M), noradrenaline-induced relaxation was not inhibited by the following antagonists: atenolol (10-6 M; selective β1-adrenoceptor antagonist), ICI-118,551 (3 × 10-8 M; selective β2-adrenoceptor antagonist), propranolol (10-7 M; non-selective β-adrenoceptor antagonist), and bupranolol (10-7 M; non-selective β-adrenoceptor antagonist). In the presence of propranolol (10-6 M), noradrenaline-induced relaxation was competitively inhibited by bupranolol (3 × 10-7-3 × 10-6 M) or SR59230A (10-7-10-6 M; selective β3-adrenoceptor antagonist), with their pA2 values calculated to be 6.64 and 7.27, respectively. None of the six noradrenaline metabolites produced significant relaxation of methacholine-contracted UBSM. These findings suggest that noradrenaline, but not its metabolites, is a ligand for β3-adrenoceptors to produce relaxation responses of UBSM in rats.

Functional effects of blocking VEGF/VEGFR2 signaling in the rat urinary bladder in acute and chronic CYP-induced cystitis.

High expression of VEGF is associated with immature angiogenesis within the urinary bladder wall and bladder afferent nerve sensitization, leading to visceral hyperalgesia and pelvic pain. Research suggests a shift in VEGF alternative splice variant (VEGF-Axxxa and VEGF-Axxxb) expression with several pathologies (e.g., neuropathic pain and inflammation) as well as differing effects on pain. Translational studies have also demonstrated increased total VEGF expression in the bladders of women with interstitial cystitis/bladder pain syndrome. In the present study, we quantified VEGF alternative splice variant expression in lower urinary tract tissues under control conditions and with cyclophosphamide (CYP)-induced cystitis. Using conscious cystometry and intravesical instillation of a potent and selective VEGF receptor 2 (VEGFR2) tyrosine kinase inhibitor (Ki-8751, 1 mg/kg) in Wistar rats (male and female) with acute and chronic CYP-induced cystitis and control (no CYP) rats, we further determined the functional effects of VEGFR2 blockade on bladder function. With VEGFR2 blockade, bladder capacity increased (P ≤ 0.01) in male and female control rats as well as in male and female rats with acute (P ≤ 0.05) or chronic (P ≤ 0.01 or P ≤ 0.05, respectively) CYP-induced cystitis. Void volume also increased in female control rats (P ≤ 0.01) and female rats with acute (P ≤ 0.05) or chronic (P ≤ 0.05) CYP-induced cystitis as well as in male control rats (P ≤ 0.05) and male rats with chronic CYP-induced cystitis (P ≤ 0.01). These data suggest that VEGF may be a biomarker for interstitial cystitis/bladder pain syndrome and that targeting VEGF/VEGFR2 signaling may be an effective treatment.

299 - Phosphorylation of CREB in dorsal root ganglia after uropathogenic Escherichia coli infection in rat urinary bladder

299 - Phosphorylation of CREB in dorsal root ganglia after uropathogenic Escherichia coli infection in rat urinary bladder

Analysis of angiotensin II-Induced rat urinary bladder contractions in the presence of angiotensin II receptors blockers

Objective An application of a specific analysis on recordings obtained from urinary bladder (UB) preparations influenced with Angiotensin II (AngII) and AngII receptor (ATR) blockers was performed. Methods UB preparations were divided as follows: group 1 stimulated with AngII only; group 2:PD123319 (ATR type-2 blocker)+AngII; group 3:Losartan (ATR type-1 blocker)+AngII. The averaged time and force parameters of the contractions were processed by a spline interpolation and graphic images of the different patterns of the contractile activity were obtained. Results The speed of AngII-induced UB contraction, when PD123319 was administered, was significantly higher than those, registered by the application of AngII alone and Losartan + AngII. The presence of Losartan markedly delayed the speed of the overall AngII-induced contraction. Conclusion The study indicates the contribution of both ATR subtypes for the development of AngII-induced UB contraction. Our results showed that probably ATR mediate a reciprocal dynamic response to AngII in the bladder.

Assessment of Inhibitory Effects of Hypnotics on Acetylcholine-Induced Contractions in Isolated Rat Urinary Bladder Smooth Muscle

The present study aimed to investigate the potential inhibitory effects of 21 clinically available hypnotics on acetylcholine (ACh)-induced contractions in rat urinary bladder smooth muscle (UBSM) in order to predict whether these hypnotics could induce voiding impairment. ACh-induced contraction in rat UBSM was inhibited only by diphenhydramine (a histamine H1 receptor antagonist) at a concentration that was clinically relevant. ACh-induced contraction was also significantly inhibited by flurazepam (a benzodiazepine hypnotic) and suvorexant (an orexin receptor antagonist), albeit at concentrations that substantially exceeded clinically achievable blood levels. These three drugs (at 10-5 M) also inhibited high-KCl (80 mM) Locke-Ringer solution-induced contractions. In contrast to the effects of the abovementioned hypnotics, ACh-induced contractions were not significantly affected by triazolam, etizolam, brotizolam, lormetazepam, estazolam, flunitrazepam, nitrazepam (benzodiazepine hypnotics), thiopental, thiamylal, pentobarbital, amobarbital, secobarbital, phenobarbital (barbiturate hypnotics), zolpidem (an imidazopyridine hypnotic), zopiclone (a cyclopyrrolone hypnotic), ramelteon (a melatonin receptor agonist), bromovalerylurea, and chloral hydrate. These findings suggest that most clinically used hypnotics are not likely to result in anticholinergic-induced dysuria within their clinically achievable blood concentration ranges. Diphenhydramine may, however, induce voiding impairment, an action attributable to diminished UBSM contractility within its clinical dose range.

Immunohistochemistry of γ-H2AX as a method of early detection of urinary bladder carcinogenicity in mice.

Phosphorylated histone H2AX (γ-H2AX) has been demonstrated as a DNA damage marker both in vitro and in vivo. We previously reported the effects of genotoxic carcinogens in the urinary bladder of rats by immunohistochemical analysis of γ-H2AX using samples from 28-day repeated-dose tests. To evaluate the application of γ-H2AX as a biomarker of carcinogenicity in the bladder, we examined species differences in γ-H2AX formation in the urinary bladder of mice. Six-week-old male B6C3F1 mice were treated orally with 12 chemicals for 4weeks. Immunohistochemical analysis demonstrated that N-butyl-N-(4-hydroxybutyl)nitrosamine, p-cresidine and 2-acetylaminofluorene (2-AAF), classified as genotoxic bladder carcinogens, induced significant increases in γ-H2AX levels in the bladder urothelium. In contrast, genotoxic (2-nitroanisole, glycidol, N-nitrosodiethylamine and acrylamide) and non-genotoxic (dimethylarsinic acid and melamine) non-bladder carcinogens did not upregulate γ-H2AX. Importantly, 2-nitroanisole, a potent genotoxic bladder carcinogen in rats, significantly increased the proportion of γ-H2AX-positive cells in rats only, reflecting differences in carcinogenicity in the urinary bladder between rats and mice. Significant upregulation of γ-H2AX was also induced by uracil, a non-genotoxic bladder carcinogen that may be associated with cell proliferation, as demonstrated by increased Ki67 expression. 2-AAF caused γ-H2AX formation mainly in the superficial layer, together with reduced and disorganized expression of uroplakin III, unlike in rats, suggesting the mouse-specific cytotoxicity of 2-AAF in umbrella cells. These results suggest γ-H2AX is a useful biomarker reflecting species differences in carcinogenicity in the urinary bladder.

Distinct differences in the mechanisms of mucosal damage and γ-H2AX formation in the rat urinary bladder treated with o-toluidine and o-anisidine.

Although aromatic amines are widely used as raw materials for dyes, some of them have been concerned about carcinogenicity in the urinary bladder. We examined early changes in histopathology and the formation of γ-H2AX, a biomarker of DNA damage, in the urinary bladder of rats to investigate the mechanisms of mucosal damage induced by monocyclic aromatic amines. 6-week-old male F344 rats were administered 0.4% or 0.8% o-toluidine, 0.3% or 1.0% o-anisidine, 0.4% 2,4-xylidine, 0.2% p-toluidine, or 0.6% aniline in the diet for 4 weeks. Animals were sequentially killed from day 2 to after 2 weeks of recovery, and histopathological and immunohistochemical analyses were performed. In the 0.8% o-toluidine group, there was sequential progression of bladder lesions, characterized by edematous changes and intramucosal hemorrhage at day 2 and formation of granulation tissue with mononuclear cell infiltration at week 1, followed by diffuse hyperplasia at weeks 2 and 4. In the 1.0% o-anisidine group, simple hyperplasia only with slight inflammation was detected from week 1. Whereas γ-H2AX-positive bladder epithelial cells in the 1.0% o-anisidine group were significantly increased in a time-dependent manner, transient increases in γ-H2AX-positive cells were detected at day 2 and week 1 in the 0.8% o-toluidine group. No apparent bladder lesions or increases in γ-H2AX formation were observed in any other groups. These results revealed different mechanisms of bladder mucosal damage associated with o-toluidine and o-anisidine. Moreover, immunohistochemical analysis for γ-H2AX suggested that both compounds may induce DNA damage in epithelial cells, mainly basal cells, of the bladder mucosa.

TRPA1 mediates the antinociceptive properties of the constituent of Crocus sativus L., safranal.

Safranal, contained in Crocus sativus L., exerts anti‐inflammatory and analgesic effects. However, the underlying mechanisms for such effects are poorly understood. We explored whether safranal targets the transient receptor potential ankyrin 1 (TRPA1) channel, which in nociceptors mediates pain signals. Safranal by binding to specific cysteine/lysine residues, stimulates TRPA1, but not the TRP vanilloid 1 and 4 channels (TRPV1 and TRPV4), evoking calcium responses and currents in human cells and rat and mouse dorsal root ganglion (DRG) neurons. Genetic deletion or pharmacological blockade of TRPA1 attenuated safranal‐evoked release of calcitonin gene‐related peptide (CGRP) from rat and mouse dorsal spinal cord, and acute nociception in mice. Safranal contracted rat urinary bladder isolated strips in a TRPA1‐dependent manner, behaving as a partial agonist. After exposure to safranal the ability of allyl isothiocyanate (TRPA1 agonist), but not that of capsaicin (TRPV1 agonist) or GSK1016790A (TRPV4 agonist), to evoke currents in DRG neurons, contraction of urinary bladder strips and CGRP release from spinal cord slices in rats, and acute nociception in mice underwent desensitization. As previously shown for other herbal extracts, including petasites or parthenolide, safranal might exert analgesic properties by partial agonism and selective desensitization of the TRPA1 channel.

Clopidogrel inhibits acetylcholine-induced contractions of urinary bladder in rat

Aim: Clopidogrel as thrombocyte Adenosine Diphosphate (ADP) receptor antagonist is used especially in peripheric artery diseases by lengthening hemorrhage time, disrupting thrombocyte aggregation and decreasing blood viscosity. It shows its antagonist effects through glycoprotein (Gp) IIb/IIIa complex ADP by preventing its activation. Although the usage area and activity is in the vascular system, there are no adequate studies showing the activity of Clopidogrel on smooth muscle contraction-relaxation mechanism. This study was conducted to investigate the effects of Clopidogrel on bladder contraction-relaxation mechanism.Material and Methods: In the present study, the bladder tissues taken from Wistar-Albino (n=7) intact female rats were used. After the decapitation, the longitudinal bladder tissues that were received 1-mm-thick, 8-mm length, and 2-mm-width, were hung in the 5-ml isolated organ bath that had Krebs-Ringer bicarbonate solution by applying 1.5 gr strain. After the bladder contractions were induced with 10 μM dose Acetylcholine (Ach), Clopidogrel was applied as two doses 0.1μM and 10μM in a noncumulative manner. The peak-to-peak (p-p) values and the values below the curve before and after the Clopidogrel application in the contraction induced with Ach were normalized as % change. The statistical analyses of the data were made in the SPSS 22.0 program by applying Paired T-Test. The p

Assessment of the inhibitory effects of antipsychotics on acetylcholine (ACh)-induced contraction in rat urinary bladder smooth muscle (UBSM)

Assessment of the inhibitory effects of antipsychotics on acetylcholine (ACh)-induced contraction in rat urinary bladder smooth muscle (UBSM)

The effects of nitrofurantoin on rat urinary bladder contraction

Nitrofurantoin is a drug used in the antibacterial treatment of urinary tract infections (UTIs) for over 60 years. The aim of our study was to investigate the possible effects of nitrofurantoin, which is commonly used as a urinary tract antiseptic, on bladder contractions in male rats. Bladder tissues obtained from male Sprague-Dawley rats were used in the study (n=24). After decapitation, bladder tissues were suspended in an isolated organ bath of 5 ml containing a Krebs-Ringer bicarbonate solution by applying a tension of 1.5 grams. Nitrofurantoin was administered to three groups at doses of 50, 500 and 1000 μM, respectively. The area, peak-to-peak (p-p) and frequency values of bladder contractions were analyzed before and after administration of nitrofurantoin. The data obtained from the analysis were evaluated using the Paired T-Test in the IBM SPSS Statistics Software. Nitrofurantoin was observed to have an inhibitory effect on bladder contractions at all doses. The decrease in the area and peak-to-peak values was statistically significant at all doses (P

Muscle cells, nerves, fibroblasts and vessels in the detrusor of the rat urinary bladder.

All the cells of rat detrusor muscle fall into one of five ultrastructural types: muscle cells, fibroblasts, axons and glia, and vascular cells (endothelial cells and pericytes). The tissue is ~79% cellular and 21% non-cellular. Muscle cells occupy 72%, nerves ~4% (1/3 axons, 2/3 glia), and fibroblast >3% of space. Muscle cells (up to 6 µm across and ~600 µm long, packed to almost 100,000 per mm2) have surface-to-volume ratio of 2.4 µm2/µm3 ~93% of cell volume is contractile apparatus, 3.1% mitochondria and 2.5% nucleus. Cell profiles are irregular but sectional area decreases regularly towards either end of the cell. Muscle cells are gathered into bundles (the mechanical units of detrusor), variable in length and size, but of constant width. The musculature is highly compact (without fascia or capsule) with smooth outer surfaces and extensive association and adhesion between its cells. Among many types of intercellular contact and junction, digitations are very common, each muscle cell issuing minute finger-like processes that abut on adjacent cells. Sealed apposition are wide areas of specialized contact, possibly forming a chamber between two muscle cells, distinct from the extracellular space at large (stromal space). The innervation is very dense, virtually all intramuscular axons being varicose (including afferent ones). There are identifiable neuro-muscular junctions on each muscle cell, often several junctions on a single cell. There are also unattached terminals. Fibroblasts (involved in the production of collagen), ~1% of the total number of cells, do not make specialized contacts.

Afferent nerve fibres in the wall of the rat urinary bladder.

Structure and distribution of afferent nerve fibres in the rat bladder were studied by fluorescence microscopy after selective staining with antibodies against neuropeptide CGRP. Afferent fibres are very abundant (by comparison with other viscera) and interconnected in all bladder parts: muscle, urothelium, connective tissue, blood vessels, serosa. Their highest concentration is beneath the urothelium in equatorial and caudal regions, where they form a plexus, while individually maintaining a tree-like structure with innumerable branches running without preferential orientation. In cranial regions, mucosal afferent fibres become rare or absent. Abundant fibres are found in the detrusor, within each muscle bundle, with long strings of varicosities parallel to muscle cells. Afferent fibres, invariably varicose over hundreds of micrometres of their terminal parts and while still branching, comprise chains of hundreds of varicosities. Varicosities are irregular in size, frequency and separation, without specialised terminal structures around them, or within or around the fibre's ending. The possibility that varicosities are transduction points for sensory inputs is discussed, with the implication of a process taking place over considerable length in each branch of each fibre. Interconnectedness of afferent nerves of various bladder tissues, distribution of varicosities over hundreds of micrometres along axonal branches, absence of clear target structures for the fibres, apparent irregularity in the size and sequence of varicosities suggest an innervation that is not rigidly wired with distinct sensory pathways. In fact, the structural evidence suggests extensive afferent integration at the periphery, with wide distribution of source points and broad range of physical detectors.