Rapid drug susceptibility testing and treatment outcomes for multidrug-resistant tuberculosis in Peru.

SETTING: The detection of multidrug-resistant tuberculosis (MDR-TB) using rapid drug susceptibility testing (DST) has increased steadily in recent years in Peru, from 9216 tests in 2010 to 27 021 tests in 2015. Research examining the impact of rapid DST on treatment outcomes is required. OBJECTIVE: To evaluate the association between rapid DST use (nitrate reductase assay, microscopic observation drug susceptibility assay [MODS] and GenoType® MTBDRplus) and treatment outcomes and mortality in MDR-TB patients in Peru. DESIGN: Retrospective cohort study of patients diagnosed with pulmonary MDR-TB between 2010 and 2013 (with treatment outcomes up to December 2015) using the electronic registry of the Peruvian National TB Programme. RESULTS: A total of 2671 MDR-TB patients were included; the median age was 27 years, 2.8% were co-infected with the human immunodeficiency virus. Use of rapid DST was associated with a 40% increase in the adjusted odds of treatment success (aOR 1.40, 95%CI 1.19-1.64) and a 54% reduction in mortality (aOR 0.46, 95%CI 0.33-0.64). Higher treatment success rates were driven by MODS and GenoType® MTBDRplus testing (aORs for unsuccessful outcomes respectively 0.68 and 0.66). CONCLUSION: The use of rapid DST (MODS and MTBDRplus) to diagnose MDR-TB was associated with a reduction in the odds of death and a substantial increase in the odds of treatment success.

A novel MPL point mutation resulting in thrombopoietin-independent activation.

Thrombopoietin (TPO) and its receptor (MPL) are important regulators of megakaryopoiesis. MPL belongs to a cytokine receptor superfamily. To date, all constitutively active MPL mutants have been artificially constructed with amino acid substitutions in the transmembrane domain or extracellular domain of the protein, and they activate signal transduction pathways in Ba/F3 cells that can also be activated by the normal MPL. In this paper, we report a novel spontaneously occurring mutation of MPL, with an amino acid substitution of Trp(508) to Ser(508) in the intracellular domain of MPL, that induces the factor-independent growth of Ba/F3 cells. Examination of intracellular signaling pathways demonstrated that the mutant MPL protein constitutively activates three distinct signaling pathways, SHC-Ras-Raf-MAPK/JNK, JAK-STAT, and PI3K-Akt-Bad.

Comparison of the angiotensin II type 1-receptor antagonist YM358 and the angiotensin-converting enzyme inhibitor enalapril in rats with cardiac volume overload.

We evaluated the effects of chronic oral administration of an angiotensin II type 1 (AT1)-receptor antagonist YM358 and an angiotensin converting enzyme inhibitor enalapril on hemodynamics and cardiac hypertrophy in rats with volume overload-induced heart failure. We assessed changes of cardiac hemodynamics and cardiac hypertrophy at 2 and 4 weeks after administration of YM358 (3, 30 mg/kg per day) or enalapril (30 mg/kg per day) in abdominal aortocaval shunt rats. YM358 (30 mg/kg) attenuated increases of left ventricle (LV)/body weight (BW), left atrium (LA)/BW, right ventricle (RV)/BW and heart/BW ratios, but did not affect cardiac hemodynamics in shunt rats. Enalapril also reduced the increased LV/BW and heart/BW ratios together with significant reductions of systolic blood pressure, left ventricular systolic pressure and the first derivative of left ventricular pressure. These data suggest that the effects on attenuation of the development of cardiac hypertrophy are not different for YM358 and enalapril, although the effects on cardiac hemodynamics are different for the same dosages. The attenuating action of YM358 on cardiac hypertrophy was independent of the action on hemodynamics and indicated the direct action of the AT1 receptor on the heart.

Effects of YM358, an angiotensin II type 1 (AT1) receptor antagonist, and enalapril on blood pressure and vasoconstriction in two renal hypertension models.

The effects of the angiotensin II type 1 receptor antagonist YM358 on blood pressure were compared to those of the angiotensin converting enzyme inhibitor enalapril in one-kidney, one-clip renal hypertensive rats (1K1C RHR), two-kidney, one-clip renal hypertensive rats (2K1C RHR) and normotensive rats (NTR). Additionally, the local drug actions in peripheral tissues were investigated using isolated mesenteric arteries from these rats. In 2K1C RHR, YM358 and enalapril produced a long-lasting hypotensive effect in a dose-dependent manner. In 1K1C RHR, YM358 (30 mg/kg) also produced an antihypertensive effect, whereas enalapril (30 mg/kg) had no effect. Administration of YM358, but not enalapril, to 1K1C RHR, 2K1C RHR and NTR did not affect heart rate. In isolated mesenteric arteries from 1K1C RHR and 2K1C RHR, angiotensin II (Ang II), angiotensin I (Ang I) and tetradecapeptide (TDP), a physiologically active renin substrate, produced concentration-dependent vasoconstriction. YM358 (10(-7) M) inhibited the vasoconstricting responses to Ang II, Ang I and TDP in isolated mesenteric arteries. In contrast, enalaprilat (10(-7) M), an active metabolite of enalapril, did not completely inhibit the response to Ang I and TDP. These results indicate that YM358 has higher efficacy than enalapril for the treatment of hypertension.

Development of a homogeneous time-resolved fluorescence assay for high throughput screening to identify Lck inhibitors: comparison with scintillation proximity assay and streptavidin-coated plate assay.

This study details the development of a homogeneous time-resolved fluorescence (HTRF) high throughput screening assay to identify inhibitors of Lck. HTRF was compared with scintillation proximity and streptavidin-coated plate assays. Because of the differences in the sensitivity of detection of phosphotyrosine among the three assays, different amounts of enzyme were used. However, the concentrations of the other assay components were standardized. When using similar assay conditions, the calculated IC(50) values of inhibitory compounds were independent of assay format. Furthermore, filtration experiments revealed that phosphorylation of a biotinyl poly-Glu,Ala, Tyr peptide substrate was less than autophosphorylation of the Lck enzyme; this was due to the low K(m) value for biotinyl poly-Glu,Ala,Tyr. In the HTRF assay, small amounts of enzyme and high concentrations of ATP could be used, thereby minimizing the effects of autophosphorylation. Higher ATP concentration would also minimize the effect of ATP competitors. Using this technology, it may be possible to find novel kinase inhibitors that do not act at the ATP binding site of protein tyrosine kinases.

Cardiovascular and renal effects of conivaptan hydrochloride (YM087), a vasopressin V1A and V2 receptor antagonist, in dogs with pacing-induced congestive heart failure.

The systemic hemodynamic and renal responses to conivaptan hydrochloride (YM087; 4'-(2-methyl-1,4,5,6-tetrahydroimidazo[4,5-d][1]benzoazepine -6-carbonyl)-2-phenylbenzanilide monohydrochloride), a vasopressin V1A and V2 receptor antagonist, were determined in pentobarbital-anesthetized dogs after 2 to 3 weeks of rapid right ventricular pacing. Congestive heart failure, characterized by decreases in first derivative of left ventricular pressure (left ventricular d P/dt(max)) and cardiac output, and increases in left ventricular end-diastolic pressure and total peripheral vascular resistance, was induced by chronic rapid right ventricular pacing at 260-280 beats/min. Intravenous administration of conivaptan (0.1 mg/kg) significantly increased left ventricular dP/dt(max) and cardiac output and significantly decreased left ventricular end-diastolic pressure and total peripheral vascular resistance. Conivaptan also increased urine flow and reduced urine osmolality by markedly increasing free water clearance. These results indicate that conivaptan produced hemodynamic improvement and marked aquaresis in dogs with congestive heart failure. Therefore, conivaptan may find clinical use in treating patients with congestive heart failure.

In vitro and in vivo vasodilatory activity of barnidipine and its enantiomers.

Barnidipine, (3'S)-1-benzyl-3-pyrrolidinyl methyl (4S)-2,6-dimethyl-4-(m-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylat e, is a dihydropyridine calcium antagonist with asymmetric carbons at the dihydropyridine C-4 and the pyrrolidine C-3' positions. In this study, the vasodilatory activity of barnidipine and its 3 optical isomers were compared in vitro and in vivo to assess the steric effects of these asymmetric carbons. All these enantiomers produced concentration-dependent relaxation on KCI (40 mM)-induced contractions in isolated guinea pig aorta with a potency order of barnidipine>(3'R,4R) approximately/= (3'R,4S)>(3'S,4R). The potency ratio between barnidipine and the (3'S,4R) enantiomer was 118. All enantiomers increased coronary blood flow after intra-arterial administration to anesthetized coronary-perfused dogs. The potency order almost agreed with that obtained in vitro, although the potency ratio between barnidipine and the (3'S,4R) enantiomer was only 15. These 4 enantiomers showed stereoselectivity for time course changes as well. The onset and disappearance of blood flow increase after intracoronary administration of barnidipine were slower than those of other enantiomers. The duration for barnidipine was longer than those for other dihydropyridine calcium antagonists such as nifedipine or nitrendipine. The present study suggests stereoselectivity for the C-4 dihydropyridine and to a lesser degree for the C-3' of pyrrolidine in an ester moiety. The steric effects of these carbons were observed not only in the potency of vasodilatory activity but also in its duration.

Ex vivo occupancy by tamsulosin of alpha1-adrenoceptors in rat tissues in relation to the plasma concentration.

At 0.5-12 h after oral administration of tamsulosin (2.3 micromol/kg) in rats, there was a significant decrease in specific [3H]prazosin binding in the prostate as compared to the control value. The greater decrease occurred in the submaxillary gland. The effect of tamsulosin was mainly due to a marked reduction of [3H]prazosin binding sites (Bmax) rather than to an increase in the dissociation constant (Kd). In contrast, there was only a slight decrease or no change in the [3H]prazosin binding in the spleen, heart, and cerebral cortex of tamsulosin-administered rats at 0.5-12 h. Oral administration of terazosin (21.7 micromol/kg) significantly increased Kd values for [3H]prazosin binding with little effect on Bmax values in the rat prostate at 3 and 6 h. The greater increases in Kd values were observed in the submaxillary gland, spleen and heart at 0.5-12 h. Terazosin had a slight effect on Kd values for the cerebral cortical [3H]prazosin binding. Tamsulosin was absorbed rapidly after oral administration at a dose of 2.3 micromol/kg in rats, and at 6 h, plasma concentration decreased markedly to approximately one-twentieth of the 0.5 h peak level. alpha1-Adrenoceptor occupancy was estimated as a percentage of decrease in Bmax values for [3H]prazosin binding in tissues of tamsulosin-treated rats compared with control rats. The alpha1-adrenoceptor occupancy by tamsulosin in the prostate and submaxillary gland occurred rapidly in parallel with the rise in plasma concentration of tamsulosin, and lasted for over 12 h despite the marked decrease in plasma concentration. Consequently, it is suggested that tamsulosin produces more selective and sustained occupancy in vivo of alpha1-adrenoceptors in the submaxillary gland and prostate of rats than in other tissues.

Effect of YM435, a dopamine DA1 receptor agonist, in a canine model of ischemic acute renal failure.

1. The effects of (-)-(S)-4-(3,4-dihydroxyphenyl)- 1,2,3,4-tetrahydroisoquinoline-7,8-diol monohydrochloride monohydrate (YM435), a dopamine DA1 receptor agonist, were evaluated in a canine model of ischemic acute renal failure (ARF). 2. ARF was induced by clamping the left renal artery for 1 hr and subsequent reperfusion of the left kidney in anesthetized uninephrectomized dogs. 3. After 1-hr complete renal artery occlusion, an intravenous infusion of either YM435 (0.3 microg/kg/ min) or 0.9% saline (vehicle) was begun and continued for 1 hr. 4. In the vehicle group, renal ischemia markedly decreased glomerular filtration rate, urine flow and urinary sodium excretion. The YM435 group was characterized by significant recoveries in glomerular filtration rate, urine flow, and urinary sodium excretion as compared with the vehicle group. 5. These results indicate that YM435 can facilitate recovery in glomerular filtration rate, urine flow, and urinary sodium excretion in a canine model of ARF induced by ischemia. YM435 may be useful in the preservation of renal function in ischemia-induced ARF.

Studies on nonpeptide angiotensin II receptor antagonists. IV. Synthesis and biological evaluation of 4-acrylamide-1H-imidazole derivatives.

A novel series of nonpeptide angiotensin II antagonists containing the acrylamide group at the 4-position of the imidazole ring was synthesized and their antagonistic activity was examined by functional assay in rabbit aorta. The acrylamide group was selected as a large lipophilic surrogate for the chloro group of EXP3174. A structure-activity relationship study of the acrylamide moiety has shown that substitution at the 4-position with the N-methyl-3,3-dimethylacrylamide group resulted in the optimal compound, 2-butyl-4-[(3,3-dimethylacryloyl)methyl-amino]-1-[[2'-(1H-tetra zol-5- yl)biphenyl-4-yl]methyl]-1H-imidazole-5-carboxylic acid (1), which was superior to EXP3174 in vitro. Since 1 showed only poor activity against angiotensin II-induced pressor response in rats after oral administration, the carboxylic acid function of 1 was converted into prodrug esters (13). Among these, the 1-[(ethoxycarbonyl)oxy]ethyl ester (13a) showed the most potent and longest-lasting activity when given orally to rats. When administered orally to conscious furosemide-treated dogs, 13a showed an approximately 3-fold increased hypotensive activity in comparison with DuP 753. These data suggest that 13a may be an useful agent for the treatment of angiotensin II-dependent diseases, such as hypertension.

Studies on nonpeptide angiotensin II receptor antagonists. III. Synthesis and biological evaluation of 5-alkylidene-3,5-dihydro-4H-imidazol-4-one derivatives.

5-Alkylidene-3,5-dihydro-4H-imidazol-4-one derivatives were synthesized and evaluated for activity as angiotensin II receptor antagonists. Substitutions at C-2 and C-5, respectively, with a propyl group and a 1-methylethylidene group resulted in the optimal compound, 3,5-dihydro-5-(1-methylethylidene)-2-propyl-3-[[2'-(1H-tetrazol - 5-yl)biphenyl-4-yl]methyl]-4H-imidazol-4-one (2b), with a pA2 value of 8.85 in rabbit aorta. When administered orally to rats, 2b showed a greater inhibitory effect on angiotensin II-induced pressor response than DuP 753. Compound 2b also showed a good antihypertensive effect when administered orally to conscious sodium-depleted spontaneously hypertensive rats, with a duration of action of 24 h. These data suggest that 2b may be a useful agent for the treatment of angiotensin II-dependent diseases such as hypertension.

Enhancement of tissue-type plasminogen activator-induced thrombolysis and prevention of reocclusion by combination with a humanized anti-glycoprotein IIb/IIIa monoclonal antibody, YM337, in a rhesus monkey model of coronary thrombosis.

We examined the effect of a humanized anti-glycoprotein IIb/IIIa monoclonal antibody, YM337, on thrombolysis with tissue-type plasminogen activator in a copper coil-induced coronary thrombosis model in rhesus monkeys. Fifty minutes after the formation of an occlusive thrombus, a test drug was administered by either i.v. bolus injection followed by continuous infusion (YM337, 0.25 mg/kg + 1.5 microg/kg/min) or i.v. bolus injection (aspirin, 17 mg/kg). Sixty minutes after induction of the occlusive thrombus, thrombolysis was initiated with tPA at a total dose of 0.5 mg/kg intravenously administered over 60 min, with 10% given as an initial bolus. The median time to reperfusion was significantly shortened by YM337 [saline, 60 min (n = 5); aspirin, 45 min (n = 5); YM337, 30 min (n = 5)]. The incidence of reocclusion was significantly decreased by YM337 (saline, 4/4; aspirin, 5/5; YM337, 1/5), and the median time to reocclusion was significantly prolonged by YM337 [saline, 30 min (n = 4); aspirin, 30 min (n = 5); YM337, 180 min (n = 5)]. YM337 significantly reduced the thrombus protein content at the end of experiment. ADP-induced platelet aggregation was completely inhibited by YM337. These results suggest that YM337 may be of clinical value as an adjunctive agent in thrombolytic therapy for patients with acute myocardial infarction.

Effect of YM435, a novel dopamine DA1 receptor agonist, in a canine model of acute congestive heart failure.

1. The effects of YM435, a dopamine DA1 receptor agonist, were evaluated in a canine model of acute congestive heart failure. 2. The model was induced in open-chest anesthetized dogs by left anterior descending coronary artery ligation, volume loading, and intravenous infusion of angiotensin II. This resulted in a moderate and stable congestive heart failure characterized by reduction in cardiac output and increases in left ventricular end-diastolic pressure and total peripheral vascular resistance. 3. Intravenous infusion of YM435 (1 microgram/kg/min) significantly decreased left ventricular end-diastolic pressure, total peripheral vascular resistance and mean blood pressure and significantly increased cardiac output and renal blood flow in this model. 4. These results indicate that intravenous infusion of YM435 can improve hemodynamics and cardiac function in a canine model of acute congestive heart failure. YM435 may be a useful therapeutic agent for the treatment of congestive heart failure.

Studies on nonpeptide angiotensin II receptor antagonists. II. Synthesis and biological evaluation of 5H-pyrazolo[1,5-b][1,2,4]triazole derivatives with a C-linked oxygen functional group at the 6-position.

2,7-Diethyl-5H-pyrazolo[1,5-b][1,2,4]triazole derivatives were synthesized and evaluated for activity as angiotensin II receptor antagonists. Replacement of the C-6 hydrogen with C-linked oxygen functional groups led to derivatives with increased in vitro activities. Among these compounds, 2,7-diethyl-5-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H- pyrazolo[1,5-b][1,2,4]triazole-6-carboxylic acid (2d) showed potent, insurmountable antagonism, but had poor oral potency against angiotensin II-induced pressor response in rats. In order to improve the oral activity, the carboxylic acid function of 2d was converted into a double ester. This modification afforded (+/-)-1-[(ethoxycarbonyl)oxy]ethyl 2,7-diethyl-5-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H- pyrazolo[1,5-b][1,2,4]-triazole-6-carboxylate (2f), which was orally active in rats, and produced a dose-dependent decrease in blood pressure when administered orally to conscious furosemide-treated dogs, with ca. 3-fold increased potency in comparison with the parent C-6 hydrogen compound.

Studies on nonpeptide angiotensin II receptor antagonists. I. Synthesis and biological evaluation of pyrazolo[1,5-b][1,2,4]triazole derivatives with alkyl substituents.

Alkyl-substituted pyrazolo[1,5-b][1,2,4]triazole derivatives were synthesized and evaluated for activity as angiotensin II receptor antagonists. Molecules with the (methylbiphenylyl)tetrazole moiety and N-5 were the preferred compounds. Ethyl substitutions at both C-2 and C-7 resulted in the optimal compound, 2,7-diethyl-5-[[2"-(1H -tetrazol-5-yl)biphenyl-4-yl]methyl]-5H-pyrazolo[1,5-b][1,2,4]tria zole (5n), with a pA2 value of 8.774 in rabbit aorta. In the in vivo tests, 5n inhibited the angiotensin II-induced pressor response in rats after oral administration. This compound also produced a dose-dependent decrease in blood pressure when administered orally to conscious furosemide-treated dogs, having a longer duration of action as compared to DuP753. These data suggest that 5a may be a useful agent for the treatment of angiotensin II-dependent disease, such as hypertension.

Antihypertensive activity of a nonpeptide angiotensin II receptor antagonist, YM358, in rats and dogs.

The antihypertensive activity of YM358, 2,7-diethyl-5-[[2'-(1 H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H-pyrazolo[1,5-b][1,2,4]tri azole potassium salt monohydrate, a new nonpeptide angiotensin II receptor antagonist, was characterized in rats and dogs. In conscious rats, YM358 after a single oral administration (1-30 mg/kg) lowered blood pressure. The rank order of hypotensive potency of YM358 in conscious rats was 2-kidney, 1-clip renal hypertensive rats > spontaneously hypertensive rats > normotensive rats on the basis of maximum hypotension. YM358 also caused decreases in blood pressure in 2-kidney, 1-clip renal hypertensive dogs and furosemide-treated dogs. Repeated administration of YM358 to 2-kidney, 1-clip renal hypertensive rats for 28 days produced a stable and long-lasting antihypertensive effect without influencing circadian blood pressure and heart rate rhythms. No reflex tachycardia was observed in any animals of either species treated with YM358. Therefore, the pharmacological profile of this compound indicates that YM358 has potential as a useful antihypertensive agent.

Pharmacological profile of YM358, a novel nonpeptide angiotensin AT1 receptor antagonist.

The pharmacological profile of YM358, 2,7-diethyl-5-[[2'-(1 H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H-pyrazolo[1,5-b][1,2,4]tri azole potassium salt monohydrate, a novel non-peptide angiotensin AT1 receptor antagonist, was studied in vitro and in vivo. YM358 competed with [125I][Sar1, Ile8]angiotensin II for angiotensin AT1 receptors in rat liver membranes. YM358 displayed competitive kinetics and the pKi value was calculated as 8.79. In contrast, YM358 had little effect on the binding of [125I][Sar1, Ile8]angiotensin II to the angiotensin AT2 receptor in bovine cerebellum. In isolated rabbit aorta, YM358 produced a parallel rightward shift in the concentration-response curve for angiotensin II with a pA2 value of 8.82. YM358 had no effect on the contraction induced by KCl, norepinephrine, serotonin, histamine, prostaglandin F2alpha or endothelin-1 even at 10(-5) M. On the basis of pKi values in the binding assay and pA2 values in the isolated tissues, YM358 was approximately 3-10 times more potent than losartan in antagonizing angiotensin AT1 receptors. In pithed rats, intravenous administration of YM358 inhibited an increase in mean blood pressure induced by intravenous infusion of angiotensin II in a dose-dependent manner. In conscious normotensive rats, YM358 at 3-30 mg/kg p.o. inhibited the angiotensin II-induced pressor response in a dose-dependent manner. YM358 at 30 mg/kg caused maximum and complete inhibition 30 min after dosing, and inhibition lasted more than 24 h. These results demonstrate that YM358 is a potent, AT1-selective and competitive nonpeptide angiotensin receptor antagonist. Moreover, YM358 is both orally active and long-lasting. This pharmacological profile suggests that YM358 would be suitable for the treatment of cardiovascular disorders such as hypertension and chronic heart failure.

Dopamine DA1 receptor agonist activity of YM435 in the canine renal vasculature.

1. The renal vasodilatory effect of YM435 was used as an index of its dopamine DA1 receptor agonist activity and compared with that of dopamine in pentobarbital-anesthetized dogs. 2. Intrarenal arterial administration of YM435 (0.1 to 10 micrograms) and dopamine (1 to 100 micrograms) produced a dose-dependent increase in renal blood flow. The doses of YM435 and dopamine required to cause a 30-ml/min increase in renal blood flow were 2.0 and 26.8 micrograms intra-arterially (IA), respectively. YM435 was therefore 13 times more potent than dopamine in this effect. 3. The selective dopamine DA1 receptor antagonist, SCH 23390, but not the selective dopamine DA2 receptor antagonist, nemonapride, caused dose-dependent, parallel shifts to the right in the dose-responsive curve of YM435. 4. The present results demonstrate that YM435 is a potent and selective dopamine DA1 receptor agonist.

Effect of alpha 1-adrenoceptor antagonists on urinary bladder function in urethane-anesthetized rats.

1. We investigated the effects of selective alpha 1-adrenoceptor antagonists on rhythmic bladder contraction and cystometrograms as representative of urinary bladder function in urethane-anesthetized rats. 2. The selective alpha 1-adrenoceptor antagonists tamsulosin (0.03-3 micrograms/kg IV), prazosin (0.03-3 micrograms/ kg IV) and bunazosin (0.03-3 micrograms/kg IV) exerted little effect on the amplitude and frequency of rhythmic bladder contraction in anesthetized rats. In contrast, the antipollakiuria agent flavoxate (5 and 10 mg/kg IV) induced a dose-dependent disappearance in frequency without affecting the amplitude of the contractions. 3. Tamsulosin (1 and 3 micrograms/kg IV), prazosin (1 and 3 micrograms/kg IV), and bunazosin (1 and 3 micrograms/kg IV) exerted no effect on the cystometrogram, either. However, flavoxate (5 and 10 mg/kg IV) raised the micturition threshold pressure and prolonged the time to micturition. 4. These results suggest that the alpha 1-adrenoceptor plays little role in urinary bladder contraction in anesthetized rats.

Responsiveness of smooth muscle in the lower urinary tract of rabbits to various agonists.

1. We compared the responsiveness of smooth muscle in the lower urinary tract and prostate from rabbits to the agonists noradrenaline, phenylephrine, clonidine, acetylcholine, prostaglandin F2 alpha, and histamine. 2. These agonists contracted smooth muscle in the lower urinary tract and prostate. In terms of maximal developed tension, contractile responses to the agonists were produced in the following order of potency: acetylcholine > prostaglandin F2 alpha > histamine > or = phenylephrine > or = noradrenaline > clonidine in the urinary bladder body; acetylcholine = noradrenaline = phenylephrine > prostaglandin F2 alpha > histamine > or = clonidine in the urinary bladder base; noradrenaline > or = phenylephrine > or = clonidine > acetyl-choline > prostaglandin F2 alpha > or = histamine in the urethra; and noradrenaline > or = phenylephrine > histamine = acetylcholine = clonidine = prostaglandin F2 alpha in the prostate. 3. These results suggest that considerable responsiveness variation occurs in the lower urinary tract and prostate and support the idea that the urinary bladder body is primarily governed by cholinergic mechanisms (parasympathetic nerves), whereas the urethra and prostate are regulated by alpha 1-adrenergic mechanisms (sympathetic nerves) and the bladder base by both.