Evaluation of nitrofurantoin on the two stages of urinary bladder carcinogenesis in the rat

The possibility that nitrofurantoin is a complete carcinogen or is an initiator or promoter of urinary bladder carcinogenesis was evaluated in male weanling F344 rats. No increase in tumor incidence was observed in rats fed nitrofurantoin at a level of 0.187% of the diet for 2 years compared to a control group. Also, no evidence of bladder initiating activity by nitrofurantoin was observed using sodium saccharin (5% of the diet) as a promoter, and no promoting activity was observed when nitrofurantoin was fed after initiation by N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (0.2% of the diet for 4 weeks). In a second experiment, nitrofurantoin (at a dose of 0.187% of the diet) was administered for 6 weeks to rats with a rapidly proliferating bladder epithelium following freeze ulceration, and then the rats were treated with 5% sodium saccharin in the diet for 98 weeks. In additional rats, labelling index following [3H]thymidine injection, determined after 12 weeks of feeding nitrofurantoin, was not increased above control levels in the urinary bladder, stomach, duodenum, or liver. Metabolism of nitrofurantoin by prostaglandin H synthase (PHS) was examined using solubilized ram seminal vesicle microsomes. The rate of nitrofurantoin metabolism by PHS was much less than that observed with benzidine, and the proportion of total metabolite bound to protein was also much less than that with benzidine. These results are consistent with previous reports describing the lack of effect of nitrofurantoin on urinary bladder carcinogenesis.     

Lack of a modifying effect by the diuretic drug furosemide on the development of neoplastic lesions in rat two-stage urinary bladder carcinogenesis

The effect of the diuretic drug furosemide on two-stage urinary bladder carcinogenesis in F344 rats initiated by N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) was investigated with regard to possible promoting activity. BBN was administered at 2 doses, 0.01 or 0.05%, in drinking water for 4 wk, and thereafter furosemide was given by gavage 3 times weekly for 32 wk, 250 mg/kg body weight. Furosemide ingestion induced diuresis with an alkaline, hypotonic urine. No significant difference with regard to incidences of bladder lesions were apparent between furosemide and control groups. The present investigation indicated that neither furosemide nor its related polyuria acted as a promoter in two-stage urinary bladder carcinogenesis.     

Content and contractile effect of arginine vasopressin in rat urinary bladder

The contractile response of normal male rat urinary bladders to exogenous arginine vasopressin (AVP) and the AVP content of normal and denervated bladders were investigated. In isolated detrusor strips, the maximal response to AVP was about 12% of the contraction elicited by KCl (124 mM), and the EC50 value was 1.03 +/- 0.13 x 10(-8) M. The response to transmural nerve stimulation was not affected by the presence of AVP. Addition of an AVP receptor antagonist strongly reduced the response to exogenous AVP, but did not affect contractions in response to nerve stimulation. In normal bladders, the concentration of immunoreactive (ir) AVP was 29 +/- 6.0 x 10(-15) mol/g. Three days after denervation the bladders had increased 2.4-fold in weight. At this time, the concentration of irAVP was not different from the control value, but the total content had increased significantly. Characterization of bladder irAVP by reverse-phase HPLC revealed that 66.5% of the total immunoreactivity eluted in the position of synthetic AVP. The results suggest a non-neuronal localization of bladder irAVP.     

Interaction of tachykinins with an adrenergic receptor in the rat urinary bladder

The rat urinary bladder was examined as a model for studying tachykinin receptors. The order of potency, the maximal effect and the slope of the dose-response curve were examined with six tachykinins - substance P (SP), physalaemin, phyllomedusin, uperolein, eledoisin, kassinin - and several substance P fragments - SP-(2-11), SP-(3-11), SP-(4-11) and SP-(6-11). The tachykinin receptor on the rat urinary bladder was shown to bind preferentially tachykinins having a hydrophilic amino acid residue in position 5-6, as occurs with physalaemin, phyllomedusin, eledoisin and kassinin. The N-terminal of the tachykinins and in particular substance P is suggested to play a major role in regulating affinity, intrinsic activity and the slope of the dose-response curve. The tachykinins are thought to exert a direct action on smooth muscle. An accessory binding site associated with the tachykinin receptor on rat urinary bladder was also identified. This accessory site binds the N-terminal amino acids of the tachykinins as well as some alpha-adrenergic compounds (phentolamine, prazosin, noradrenaline or adrenaline in the presence of propranolol). When the accessory binding site is occupied by adrenergic compounds, the affinity of the tachykinins is markedly reduced. This observation is interpreted to mean that catecholamines may have a modulatory influence on tachykinin activity on the rat urinary bladder.     

Effects of St John's wort and its active constituents,hypericin and hyperforin,on isolated rat urinary bladder

Objectives To investigate the effect of St John's wort (SJW) and its active constituents hypericin and hyperforin on detrusor smooth muscle contractility and their possible neuroprotective role against ischaemic‐like conditions, which could arise during overactive bladder disease. Methods In whole bladders, intrinsic nerves underwent electrical field stimulation (EFS). The effect of drugs on the contractile response and its recovery in reperfusion phase (R) was monitored at different concentrations during 1 or 2 h of anoxia‐glucopenia (A‐G) and the first 30 min of R. The effects of the drugs were also investigated on rat detrusor muscle strips contracted with carbachol, KCl and electrically. Key Findings SJW has spasmolytic activity, which increases with increasing concentration and it worsens the damage induced by A‐G/R on rat urinary bladder. Hypericin and hyperforin had no effect during ischemic‐like conditions but they both exert a dual modulation of rat detrusor strips contraction. At high micromolar concentrations they showed a relaxing effect, but at submicromolar range hypericin increased the plasma membrane depolarisation and hyperforin showed a stimulatory effect on the cholinergic system. Conclusions The results of our study showed that SJW and its constituents could modulate urinary bladder contractility and even worsen A‐G/R injury.     

Enhancing effect of thiabendazole on urinary bladder carcinogenesis induced by sodium o-phenylphenate in F344 rats

Sodium o-phenylphenate (OPP-Na), a urinary bladder carcinogen in rats, and another fungicide, thiabendazole (TBZ) were fed separately or simultaneously to F344/DuCrj rats of both sexes. The rats were fed one of six diets, either the basal (control) diet or basal diet containing 0.2% TBZ (group T), 1% OPP-Na (1% SO), 2% OPP-Na (2% SO), 1% OPP-Na plus 0.2% TBZ (1% SO-T) or 2% OPP-Na plus 0.2% TBZ (2% SO-T) for 13 or 65 wk. In the 13-wk study, in which groups of ten rats of each sex were used, urinary bladder tumours appeared in 8/10 males in each of three groups--the 2% SO, 1% SO-T and 2% SO-T groups--but not in the remaining animals. Of these tumours, carcinoma accounted for 3/8 tumours in the 2% SO group, 2/8 in the 1% SO-T group and 8/8 in the 2% SO-T group. In the 65-wk study, in which groups of 15 rats were used, the tumour incidence in males was 1/15 in the T group and 15/15, 12/15 and 14/15 in the 2% SO, 1% SO-T and 2% SO-T groups, respectively, while in the females, tumours were found in 2/15, 1/15 and 12/15 animals in the 2% SO, 1% SO-T and 2% SO-T groups, respectively. Of these tumours, carcinoma accounted for 10/15, 11/12 and 10/14 in the males of the 2% SO, 1% SO-T and 2% SO-T groups, respectively, and for 1/2 and 6/12 in the 2% SO and 2% SO-T females, respectively. The tumour incidences in the 1% SO-T males in the two studies and in the 2% SO-T females in the 65-wk study showed a statistically significant increase over those in the 1% SO males or the 2% SO females. Thus, TBZ apparently enhanced the carcinogenic effects of OPP-Na in the rat urinary bladder.     

Evidence for a capsaicin-sensitive, tachykinin-mediated, component in the NANC contraction of the rat urinary bladder to nerve stimulation.

1. In the presence of atropine (1 microM) and guanethidine (3 microM), electrical field stimulation (EFS) of the rat isolated urinary bladder for 30 s induced a frequency-dependent (1-30 Hz) nonadrenergic non-cholinergic (NANC) triphasic contraction characterized by a peak response (within 10 s from onset of stimulation), a late response (determined as the tension developed at the end of the stimulation period) and a prolonged post-stimulus 'off' response. The latter peaked at 2-6 min from the end of the stimulation period. At 10 Hz, the amplitude of the three responses averaged 89 +/- 6, 76 +/- 6 and 18 +/- 3% of the response to 40 mM KCl, respectively. Tetrodotoxin (1 microM) abolished all contractile responses to EFS. 2. In capsaicin-pretreated bladder strips (10 microM for 15 min) the amplitude of the peak response to EFS (1-30 Hz for 30 s) was unchanged, the 'late' response to EFS was significantly reduced as compared to controls, and the post-stimulus response was absent, being replaced by a transient relaxation. 3. When varying train duration from 1 to 120 s at a frequency of 10 Hz, the differences between control and capsaicin-treated strips became evident for periods of stimulation > 10 s. 4. The tachykinin NK1 receptor antagonist, SR 140,333 (0.1-1 microM) had no effect on the peak response to EFS (10 Hz for 30 s) while it decreased significantly the late response at both concentrations tested (16 +/- 3 and 33 +/- 3% inhibition).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of troxypyrrolidinium,a choline uptake inhibitor,on the excitatory innervation of the rat urinary bladder

Troxypyrrolidinium, a choline uptake inhibitor, reduced but failed to abolish responses of the rat urinary bladder to electrical stimulation at 1–100 Hz although it reduced acetylcholine output during stimulation at 10 Hz to a level similar to that of spontaneous release. Inhibition of the response to stimulation was more complete at faster rates of stimulation and was partially reversed by choline. Troxypyrrolidinium produced a greater inhibition of the ‘tonic’ component of the response to electrical stimulation than of the ‘phasic’ component. Hemicholinium-3 or hyoscine produced a similar selective effect on the ‘tonic’ component. Hemicholinium-3 also reduced acetylcholine output during electrical stimulation to a similar extent as troxypyrrolidinium but hyoscine increased transmitter output. The results support the concept of a second transmitter in the excitatory innervation of the bladder.     

Motor effects of loperamide on rat urinary bladder: an in vitro study

Motility recordings in muscle strips from rat urinary bladder were performed and the effect of the opiate agonist loperamide on motor activity was studied. Loperamide induced a concentration-dependent (10(-7)-10(-3) M) inhibition of the contractile response of the detrusor strip of the same order of magnitude after activation of intramural nerves, stimulation of cholinergic receptors with acetylcholine and after direct depolarisation of the cell with potassium. Pretreatment with the opiate-antagonist naloxone (10(-5) M) did not antagonise the inhibitory action of loperamide on bladder motility regardless of the type of activation. Naloxone per se, however, facilitated the nerve-mediated motor response. The inhibitory action of loperamide on the potassium-induced contraction could partly be counteracted by elevation of the calcium concentration in the medium. It is suggested that the demonstrated inhibitory effect of loperamide on bladder motility is a calcium-dependent direct smooth muscle action, without any significant opiate-receptor-mediated action in the present in vitro preparation.     

The effect of peripherally administered GABA on spontaneous contractions of rat urinary bladder in vivo

• 1.1. Intravenous GABA suppresses the spontaneous contractions of rat urinary bladder produced by saline loading (micturition reflex) without possessing any significant inhibitory effect on spontaneous and stimulated (neuro-hormones and field stimulation) contraction of rat detrusor strips in vitro.
• 2.2. The in vivo effects of GABA, in view of the results obtained with atropine, hexamethonium and tetrodotoxin in the same experimental conditions, are likely to be ascribable to an action at pelvic ganglia level.

     

The effect of streptozotocin-induced diabetes on cholinergic motor transmission in the rat urinary bladder.

1. The effect of streptozotocin (STZ)-induced diabetes on cholinergic motor transmission in the rat urinary bladder was investigated by recording contractile activity of detrusor strips in vitro. 2. The Ca(2+)-channel antagonist, nifedipine, was found to be more effective in blocking the noncholinergic motor transmission than P2-purinoceptor desensitization by alpha,beta-methylene ATP. 3. The neurogenic contractile responses to electrical field stimulation in the presence of nifedipine (cholinergic) were larger in the diabetic detrusor than in the non-diabetic controls. The potentiation of the cholinergic transmission was more evident at higher frequencies. 4. Concentration-response curves for acetylcholine were identical in detrusors from diabetic and non-diabetic animals, thus excluding a postsynaptic supersensitivity to acetylcholine being responsible for the potentiation of cholinergic motor transmission. 5. It is concluded that the potentiation of cholinergic motor transmission is due to enhanced release of acetylcholine in diabetic detrusor. Possible reasons for this enhancement are discussed in relation to diabetes.     

ZMS对老年大鼠脑内NGF和BDNF的影响

目的　研究自然衰老大鼠脑内两种神经营养素与学习记忆的关系 ,以及中药活性成分ZMS的作用。方法　用Y 迷宫测试动物的学习记忆功能 ,酶联免疫吸附分析法测定脑组织中BDNF和NGF的含量。结果　老年大鼠的学习和记忆成绩比青年大鼠差 (P <0 0 1) ,脑组织中BDNF的水平降低 ,NGF的变化无显著性。老年鼠喂服ZMS 2mon后 ,学习和记忆能力改善 ,正确次数 /反应总时间比值提高 (P <0 0 1) ,同时BDNF含量也高于老年组 (P <0 0 1)。但是ZMS对脑内NGF含量无影响。结论　ZMS能提高增龄引起的脑BDNF降低 ,从而对神经元起保护作用 ,这可能是ZMS改善老年大鼠学习记忆功能的重要机制之一     

Extremely low bioavailability of magnesium lithospermate B, an active component from Salvia miltiorrhiza, in rat

We assessed the bioavailability of magnesium lithospermate B (MLB), a main polyphenolic component of Salvia miltiorrhiza and a potent antioxidant having various pharmacological activities, to evaluate its action in vivo. The plasma concentrations of lithospermic acid B (LSB) showed a biexponential decrease after intravenous administration of MLB to rats at doses of 4 and 20 mg/kg. The values of area under the concentration-time curve (AUC; 87.8 +/- 10.9 and 1130 +/- 329 microg.min/mL), total body clearance (CL (tot); 55.52 +/- 7.07 and 23.51 +/- 5.98 mL/min/kg), and distribution volume at steady state (V (ss); 7.60 +/- 1.03 and 3.61 +/- 1.16 L/kg) suggested non-linear pharmacokinetics between the two doses. After oral administration of MLB at a high dose of 100 mg/kg, the mean AUC was barely 1.26 +/- 0.36 microg.min/mL. Absolute bioavailability of MLB was calculated to be 0.0002 from the AUC values after both intravenous dosing at 20 mg/kg and oral dosing at 100 mg/kg. The extremely low bioavailability was caused mainly by poor absorption from the rat gastrointestinal tract; about 65 % of the dose was retained in the tract even 4 h after oral administration, and most of the dose was retained even 20 min after infusion in an in situ jejunal loop experiment. Urinary and biliary excretion of LSB were only 0.70 % +/- 0.26 % and 5.10 % +/- 2.36 %, respectively, over a 30 h time period after intravenous injection despite the large CL (tot) and V (ss) values, and were much less (0.010 % +/- 0.001 % and 0.12 % +/- 0.04 %) after oral dosing. These findings suggest that extensive metabolism, including a first-pass effect, and wide distribution of LSB besides the poor absorption contributed significantly to the extremely low systemic bioavailability.     

Effects of urinary crystals induced by acetazolamide, uracil, and diethylene glycol on urinary bladder carcinogenesis in N-butyl-N-(4-hydroxybutyl)nitrosamine-initiated rats

In order to examine the promoting effect of urinary crystals on urinary bladder carcinogenesis, acetazolamide, uracil, and diethylene glycol, all of which have been reported to cause urinary crystals or calculi, were administered to male F344 rats for 32 weeks after pretreatment with 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) for 4 weeks. A marked increase in urinary crystals was observed in acetazolamide-treated rats and a slight increase in crystals was observed in uracil- and diethylene glycol-treated rats. Histological examination of the urinary bladder revealed that the BBN-acetazolamide treatment resulted in a higher incidence of carcinoma than BBN-control. Uracil and diethylene glycol did not cause any significant difference compared to the control. Promoting effects by urinary crystals were not clearly shown in the present experiment and, therefore, urinary crystals appear to play a very limited role, if any, in urinary bladder carcinogenesis.     

Inhibitory effect of sodium nitroprusside on the relaxing action of isoproterenol in isolated rat urinary bladder

1. Isoproterenol caused relaxation of rat detrusor muscles contracted by electrical stimulations. Sodium nitroprusside (SNP) and methylene blue inhibited the relaxation induced by isoproterenol without affecting forskolin-induced relaxation.2. In the presence of theophylline, zaprinast still potentiated isoproterenol-relaxation. In the presence of butoxamine, a selective β₂-adrenoceptor inhibitor, but not metoprolol, a selective β₁-adrenoceptor inhibitor, SNP still inhibited isoproterenol-relaxation.3. SNP inhibited the relaxation to dobutamine, a β₁-adrenoceptor agonist, but not that to terbutaline, a β₂-adrenoceptor agonist. The relaxation to dobutamine was also inhibited by methylene blue. Further, in the presence of theophylline, zaprinast still potentiated dobutamine-relaxation.4. Isoproterenol increased tissue level of cGMP, which was inhibited by propranolol.5. These results suggest a possibility that, in rat detrusor muscles, isoproterenol causes relaxation due to increases in the level of both cAMP and cGMP.     

Potential effects of the herbicide Diuron on mammary and urinary bladder two-stage carcinogenesis in a female Swiss mouse model

The potential promoting effect of Diuron was investigated in a mouse model of mammary and urinary bladder carcinogenesis induced by 7,12-dimethylbenz(a)anthracene (DMBA) and N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). Four-week old female Swiss mice were allocated to five groups: Groups G1-G3 received DMBA (5 × 1.5 mg/mouse) and BBN (8 × 7.5 mg/mouse) and G4 and G5 groups received only vehicles during the first 6 weeks. At week 7, G1 and G5 groups received basal diet and G2, G3 and G4 groups were fed a diet containing Diuron at 1,250, 2,500 and 2,500 ppm, respectively, during 13 weeks. At week 20, the animals were euthanized and the gross tumors were registered. Mammary glands and urinary bladder were processed for histopathological analysis. Samples from non-tumor areas were evaluated for cell proliferation by 5-bromodeoxyuridine labeling index (BrdU-LI%) and apoptosis. Dietary treatment with Diuron at 1,250 and 2,500 ppm significantly increased BrdU-LI% (P < 0.05) and the incidence of simple/nodular urothelial hyperplasia in the urinary bladder from DMBA/BBN-initiated groups (G2 and G3 vs. G1, P < 0.02) and in the non-initiated group (G4 vs. G5, P = 0.042). Two transitional cell carcinomas were observed in the group initiated and fed Diuron 2,500 ppm (G3). In contrast, in the mammary gland, Diuron feeding for 13 weeks did not significantly alter cell proliferation and apoptosis indexes or the incidence of hyperplastic lesions or neoplasms in the DMBA/BBN-initiated groups. These findings suggest that Diuron is a promoting agent to the urinary bladder but not to the mammary gland in female Swiss mice submitted to a medium-term two-stage carcinogenesis bioassay.     

Diuron-induced rat urinary bladder carcinogenesis: Mode of action and human relevance evaluations using the International Programme on Chemical Safety framework

Diuron, a high volume substituted urea herbicide, induced high incidences of urinary bladder carcinomas and low incidences of kidney pelvis papillomas and carcinomas in rats exposed to high doses (2500 ppm) in a 2-year bioassay. Diuron is registered for both occupational and residential uses and is used worldwide for more than 30 different crops. The proposed rat urothelial mode of action (MOA) for this herbicide consists of metabolic activation to metabolites that are excreted and concentrated in the urine, leading to cytotoxicity, urothelial cell necrosis and exfoliation, regenerative hyperplasia, and eventually tumors. We show evidence for this MOA for diuron using the International Programme on Chemical Safety (IPCS) conceptual framework for evaluating an MOA for chemical carcinogens, and the United States Environmental Protection Agency (USEPA) and IPCS framework for assessing human relevance.