Effect of YM087, a potent nonpeptide vasopressin antagonist, on vasopressin-induced protein synthesis in neonatal rat cardiomyocyte.

OBJECTIVE: Hypertrophy of cardiomyocytes may play an important role in the pathogenesis of cardiac hypertrophy associated with various cardiovascular diseases such as congestive heart failure. The aim of this study was to investigate whether vasopressin (AVP) induces protein synthesis in cultured neonatal rat cardiomyocytes through its specific receptor and whether YM087, a newly synthesized nonpeptide AVP receptor antagonist, inhibits AVP-induced protein synthesis in vitro. METHODS: AVP receptors on cardiomyocytes were characterized using the radioligand [3H] AVP. The effects of AVP and YM087 on intracellular free calcium concentration ([Ca2+]i), mitogen-activated protein (MAP) kinase and [3H]-leucine incorporation were investigated in cultured neonatal rat cardiomyocytes. RESULTS: In cardiomyocytes, Scatchard analysis showed a single population of high-affinity binding sites with the expected AVP V1A receptor subtype profile. YM087 showed high affinity for cardiomyocyte V1A receptors with a Ki value of 0.63 nM. In these same cells, YM087 potently inhibited AVP-induced increases in [CA2+]I and activation of MAP kinase in a concentration-dependent manner. In addition, AVP concentration-dependently stimulated the synthesis of protein without changing the rate of DNA synthesis, and YM087 prevented AVP-induced protein synthesis in a concentration-dependent manner. CONCLUSIONS: These results suggest that AVP directly causes protein synthesis and YM087 is a potent inhibitor of AVP-induced protein synthesis of cardiomyocytes and thus may have beneficial effects in the development and regression of cardiomyocytic hypertrophy.

Pharmacological characterization of the human vasopressin receptor subtypes stably expressed in Chinese hamster ovary cells.

Three subtypes of human (h) arginine vasopressin (AVP) receptors, hV1A, hV1B and hV2, were stably expressed in Chinese hamster ovary (CHO) cells and characterized by [3H]-AVP binding studies. In addition, the coupling of the expressed receptor protein to a variety of signal transduction pathways was investigated. Scatchard analysis of saturation isotherms for the specific binding of [3H]-AVP to membranes, prepared from CHO cells transfected with hV1A, hV1B and hV2 receptors, yielded an apparent equilibrium dissociation constant (Kd) of 0.39, 0.25 and 1.21 nM and a maximum receptor density (Bmax) of 1580 fmol mg(-1) protein, 5230 fmol mg(-1) protein and 7020 fmol mg(-1) protein, respectively. Hill coefficients did not differ significantly from unity, suggesting binding to homogenous, non-interacting receptor populations. Pharmacological characterization of the transfected human AVP receptors was undertaken by measuring the relative ability of nonpeptide AVP receptor antagonists, YM087, OPC-21268, OPC-31260, SR 49059 and SR 121463A, to inhibit binding of [3H]-AVP. At hV1A receptors, the relative order of potency was SR49059>YM087>OPC-31260>SR 121463A> >OPC-21268 and at hV2 receptors, YM087=SR 121463A>OPC-31260>SR 49059> >OPC-21268. In contrast, the relative order of potency, at hV1B receptors, was SR 49059> >SR 121463A=YM087=OPC-31260=OPC-21268. In CHO cells expressing either hV1A or hV1B receptors, AVP caused a concentration-dependent increase in intracellular Ca2+ concentration ([Ca2+]i) with an EC50 value of 1.13 nM and 0.90 nM, respectively. In contrast, stimulation of CHO cells expressing hV2 receptors resulted in an accumulation of cyclic AMP with an EC50 value of 2.22 nM. The potency order of antagonists in inhibiting AVP-induced [Ca2+]i or cyclic AMP response was similar to that observed in radioligand binding assays. In conclusion, we have characterized the pharmacology of human cloned V1A, V1B and V2 receptors and used these to determine the affinity, selectivity and potency of nonpeptide AVP receptor antagonists. Thus they may prove to be a valuable tool in further examination of the physiological and pathophysiological roles of AVP.

Effects of YM471, a nonpeptide AVP V(1A) and V(2) receptor antagonist, on human AVP receptor subtypes expressed in CHO cells and oxytocin receptors in human uterine smooth muscle cells.

YM471, (Z)-4'-[4,4-difluoro-5-[2-(4-dimethylaminopiperidino)-2-oxoethylidene]-2,3,4,5-tetrahydro-1H-1-benzoazepine-1-carbonyl]-2-phenylbenzanilide monohydrochloride, is a newly synthesized potent vasopressin (AVP) receptor antagonist. Its effects on binding to and signal transduction by cloned human AVP receptors (V(1A), V(1B) and V(2)) stably expressed in Chinese hamster ovary (CHO) cells, and oxytocin receptors in human uterine smooth muscle cells (USMC) were studied. YM471 potently inhibited specific [(3)H]-AVP binding to V(1A) and V(2) receptors with K(i) values of 0.62 nM and 1.19 nM, respectively. In contrast, YM471 exhibited much lower affinity for V(1B) and oxytocin receptors with K(i) values of 16.4 microM and 31.6 nM, respectively. In CHO cells expressing V(1A) receptors, YM471 potently inhibited AVP-induced intracellular Ca(2+) concentration ([Ca(2+)](i)) increase, exhibiting an IC(50) value of 0.56 nM. However, in human USMC expressing oxytocin receptors, YM471 exhibited much lower potency in inhibiting oxytocin-induced [Ca(2+)](i) increase (IC(50)=193 nM), and did not affect AVP-induced [Ca(2+)](i) increase in CHO cells expressing V(1B) receptors. Furthermore, in CHO cells expressing V(2) receptors, YM471 potently inhibited the production of cyclic AMP stimulated by AVP with an IC(50) value of 1.88 nM. In all assays, YM471 showed no agonistic activity. These results demonstrate that YM471 is a potent, nonpeptide human V(1A) and V(2) receptor antagonist which will be a valuable tool in defining the physiologic and pharmacologic actions of AVP.

Pharmacologic characterization of the oxytocin receptor in human uterine smooth muscle cells.

[(3)H]-oxytocin was used to characterize the oxytocin receptor found in human uterine smooth muscle cells (USMC). Specific binding of [(3)H]-oxytocin to USMC plasma membranes was dependent upon time, temperature and membrane protein concentration. Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high-affinity binding sites with an apparent equilibrium dissociation constant (K(d)) of 0.76 nM and a maximum receptor density (B(max)) of 153 fmol mg(-1) protein. The Hill coefficient (n(H)) did not differ significantly from unity, suggesting binding to homogenous, non-interacting receptor populations. Competitive inhibition of [(3)H]-oxytocin binding showed that oxytocin and vasopressin (AVP) receptor agonists and antagonists displaced [(3)H]-oxytocin in a concentration-dependent manner. The order of potencies for peptide agonists and antagonists was: oxytocin>[Asu(1,6)]-oxytocin>AVP= atosiban>d(CH(2))(5)Tyr(Me)AVP>[Thr(4),Gly(7)]-oxytocin>dDAVP, and for nonpeptide antagonists was: L-371257>YM087>SR 49059>OPC-21268>SR 121463A>OPC-31260. Oxytocin significantly induced concentration-dependent increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) and hyperplasia in USMC. The oxytocin receptor antagonists, atosiban and L-371257, potently and concentration-dependently inhibited oxytocin-induced [Ca(2+)](i) increase and hyperplasia. In contrast, the V(1A) receptor selective antagonist, SR 49059, and the V(2) receptor selective antagonist, SR 121463A, did not potently inhibit oxytocin-induced [Ca(2+)](i) increase and hyperplasia. The potency order of antagonists in inhibiting oxytocin-induced [Ca(2+)](i) increase and hyperplasia was similar to that observed in radioligand binding assays. In conclusion, these data provide evidence that the high-affinity [(3)H]-oxytocin binding site found in human USMC is a functional oxytocin receptor coupled to [Ca(2+)](i) increase and cell growth. Thus human USMC may prove to be a valuable tool in further investigation of the physiologic and pathophysiologic roles of oxytocin in the uterus. British Journal of Pharmacology (2000) 129, 131 - 139

Binding characteristics of YM087, an AVP receptor antagonist, in rhesus monkey liver and kidney membranes.

The binding characteristics of YM087, a nonpeptide vasopressin (AVP) V1A and V2 receptor antagonist, were studied using 3H-AVP binding to rhesus monkey liver and kidney membrane preparations. Both membrane preparations exhibited one class of high-affinity binding sites. However each membrane's receptors were different, with Kd values of 0.57 and 1.11 nM, Bmax values of 59.6 and 147 fmol/mg protein for liver and kidney, respectively. AVP receptor agonist or antagonist binding inhibition studies confirmed that these receptors belong to the V1A (liver) and V2 (kidney) subtypes. YM087 showed high affinity for both liver V1A and kidney V2 receptors with Ki values of 26.3 and 9.89 nM, respectively. These results show that YM087 is a potent, nonpeptide dual AVP V1A and V2 receptor antagonist, and would be a powerful tool for understanding the physiologic roles of AVP.

Characterization of rodent liver and kidney AVP receptors: pharmacologic evidence for species differences.

Radioligand binding studies with [3H]vasopressin (AVP) were used to determine the affinities of AVP receptor agonists and antagonists for mouse liver and kidney plasma membrane preparations. Both membrane preparations exhibited one class of high-affinity binding site. AVP ligand binding inhibition studies confirmed that mouse liver binding sites belong to the V1A subtype while kidney binding sites belong to the V2 receptor subtype. The affinity of each ligand for mouse V1A receptors was very similar to that for rat V1A receptors, showing differences in Ki values of less than 3-fold. In contrast, several peptide (d(CH2)5Tyr(Me)AVP) and nonpeptide (OPC-21268 and SR 49059) ligands had different affinities for mouse and rat kidney V2 receptors, with differences in Ki values ranging from 14- to 17-fold. These results indicate that mouse and rat kidney V2 receptors show significant pharmacologic differences.

Characterization of vasopressin receptor in rat lung.

This study characterized rat lung membrane arginine vasopressin (AVP) receptors in detail. Specific binding of [3H]AVP to rat lung membranes was dependent upon time, temperature and membrane protein concentration. Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high-affinity binding sites with a Kd of 0.45 nM and a Bmax of 76.6 fmol/mg protein. Competitive inhibition of [3H]AVP binding showed that neurohypophysial hormones as well as their synthetic analogues displaced [3H]AVP in a concentration-dependent manner. The order of potencies for the native peptides was: AVP > lysine vasopressin = arginine vasotocin > oxytocin. Furthermore, potent V1A receptor antagonists, d(CH2)5Tyr(Me)AVP and dPTyr(Me)AVP, showed high affinity for lung membranes. In contrast, the V2 receptor agonist, dDAVP, and the specific oxytocin receptor agonist, [Thr4,Gly7]oxytocin, did not affect AVP binding. These results suggest that the lung contains the V1A receptor subtype. The lung membrane AVP receptor characterized in this study may play an important role in mediating the physiological effects of AVP in the lung.

Pharmacological profile of YM087, a novel nonpeptide dual vasopressin V1A and V2 receptor antagonist, in dogs.

The pharmacological profile of YM087 (4'-[(2-methyl-1,4,5,6-tetrahydroimidazo[4,5-d][1]benzazepin -6-yl) carbonyl]-2-phenylbenzanilide monohydrochloride) was investigated in dogs. YM087 showed high affinity for vasopressin V1A and V2 receptors in radioligand receptor binding studies with dog platelets (V1A) and kidney (V2). Intravenously injected YM087 (3-100 micrograms/kg) dose dependently inhibited the pressor response to exogenous vasopressin in anesthetized dogs. Intravenous (10-100 micrograms/kg) and oral (30-300 micrograms/kg) administration of YM087 dose dependently increased urine flow with little effect on urinary sodium and potassium excretion in normally hydrated conscious dogs. Concomitantly, the urine osmolality dropped below the plasma osmolality (300 mOsm/kg H2O). In contrast, intravenously injected furosemide (300 micrograms/kg) increased urine flow with marked increases in urinary sodium and potassium excretion. These results indicate that YM087 is the first orally effective dual vasopressin V1A and V2 receptor antagonist and that it will be a new tool in the investigation of the physiological and pathophysiological role of vasopressin in the cardiovascular system and kidney. YM087 may be useful for the treatment of patients with congestive heart failure, renal diseases and water-retaining diseases.

Renal effect of YM435, a new dopamine D1 receptor agonist, in anesthetized dogs.

The renal effects of YM435 ((-)-(S)-4-(3,4-dihydroxyphenyl)-7,8-dihydroxy -1,2,3,4-tetrahydroisoquinoline hydrochloride hydrate), a dopamine D1 receptor agonist, were investigated in anesthetized dogs. Intravenous infusion of YM435 (0.1-3 micrograms/kg per min) increased renal blood flow and decreased mean blood pressure in a dose-dependent manner with little effect on heart rate. Glomerular filtration rate, urine flow and urinary sodium excretion were concomitantly increased. The renal effect of YM435 by intravenous infusion at 0.3 microgram/kg per min was completely blocked by treatment with the selective dopamine D1 receptor antagonist SCH 23390 (7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazep ine hydrochloride). Furthermore, intravenous infusion of YM435 (0.3 microgram/kg per min) reversed the angiotensin II-induced decreases in renal blood flow, glomerular filtration rate, urine flow and urinary sodium excretion, and prevented the decrease in renal blood flow, glomerular filtration rate and urine flow induced by renal nerve stimulation and platelet-activating factor (PAF). These results suggest that intravenous administration of YM435 produces renal vasodilating and diuretic/natriuretic effects by stimulation of dopamine D1 receptors, and demonstrate that YM435 can inhibit angiotensin II-, renal nerve stimulation- and PAF-induced renal dysfunction.

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.

Comparison of vasopressin binding sites in human uterine and vascular smooth muscle cells.

Several studies indicate that oxytocin and vasopressin receptors in the human uterus are heterogeneous. We have investigated whether oxytocin and vasopressin bind to separate receptors or one class of receptors in human uterine smooth muscle cells. [3H]d(CH2)5Tyr(Me)AVP, the vasopressin V1A receptor selective radioligand, was used for comparison of vasopressin binding sites in human uterine and vascular smooth muscle cell membranes. Both membrane preparations exhibited one class of high-affinity binding sites with Kd values of 6.44 and 0.47 nM, Bmax values of 166 and 34.8 fmol/mg protein for uterine and vascular smooth muscle cells, respectively. In vascular preparations, the selective vasopressin V1A receptor antagonist, SR 49059 ((2S) 1-[(2R 3S)-(5-chloro-3-(2-chlorophenyl)- -(3.4-dimethoxybenzenesulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2- carbonyl]-pyrrolidine-2-carboxamide), showed high affinity with Ki value of 0.98 nM, confirming that these receptors belong to the vasopressin V1A receptor subtype. On the contrary, in uterine preparations, binding of [3H]d(CH2)5Tyr(Me)AVP was more effectively displaced by oxytocin and the oxytocin receptor selective antagonist, L-371257, (1-[1-[4-[ N-Acetyl-4-piperidinyl)oxy]2-methoxybenzoyl]piperidin-4-yl]- 4H-3,1-benzoxazin-2(1H)-one), than vasopressin and SR 49059, suggesting that binding may be due to cross-reaction with the oxytocin receptors. These results suggest that human uterine smooth muscle cells express only a high density of oxytocin receptors.

Vasopressin increases vascular endothelial growth factor secretion from human vascular smooth muscle cells.

Vascular endothelial growth factor (VEGF) is a potent and specific mitogen of vascular endothelial cells which promotes neovascularization in vitro. To determine whether vasopressin induces VEGF secretion in human vascular smooth muscle cells, we performed enzyme-linked immunosorbent assays. Vasopressin potently induced a time-dependent and concentration-dependent (maximal, 10(-7) M) increase in VEGF secretion by human vascular smooth muscle cells that was maximal after 24 h. Furthermore, vasopressin also concentration-dependently caused mitogenic effect, as reflected by total protein content of cells per culture well. These vasopressin-induced VEGF secretion increase and mitogenic effect of these cells were potently inhibited by vasopressin V1A receptor antagonists, confirming this is a vasopressin V1A receptor-mediated event. These results indicate that vasopressin increases VEGF secretion in human vascular smooth muscle cells, the magnitude of VEGF secretion being temporally related to the mitogenic effect of vascular smooth muscle cells and the potency of the growth-promoting stimulus. Vasopressin-induced VEGF secretion by proliferating vascular smooth muscle cells could act as a paracrine hormone to powerfully influence the permeability and growth of the overlying vascular endothelium, vasopressin play a more fundamental role in the regulation of vascular function than has previously been recognized.

Pharmacological characterization of YM087, a potent, nonpeptide human vasopressin V1A and V2 receptor antagonist.

The effects of YM087 (4'-[(2-methyl-1,4,5,6-tetrahydroimidazo[4,5-d] [1]benzazepin-6-yl)-carbonyl]-2-phenylbenzanilide monohydrochloride), a novel nonpeptide vasopressin (AVP) receptor antagonist, on [3H]AVP binding to human AVP receptors (V1A, V1B and V2) cloned and transiently expressed in COS-1 cells generated from monkey renal tissue were studied. Scatchard analysis of saturation isotherms for the specific binding of [3H]AVP to membranes, prepared from COS-1 cells transfected with human V1A, V1B and V2 receptors, yielded an apparent equilibrium dissociation constant (Kd) of 0.67 nM, 0.28 nM and 2.14 nM and a maximum receptor density (Bmax) of 2180 fmol/mg protein, 369 fmol/mg protein and 2660 fmol/mg protein, respectively. YM087 showed high affinity for AVP V1A and V2 receptors with Ki values of 6.3 and 1.1 nM, respectively, but had no effect on [3H]AVP binding to AVP V1B receptors. In COS-1 cells expressing either AVP V1A or V1B receptors, AVP caused a concentration-dependent increase in intracellular Ca2+ concentration ([Ca2+]i). YM087 inhibited the AVP-induced increase in [Ca2+]i in COS-1 cells expressing AVP V1A receptors in a concentration-dependent manner with an IC50 value of 14.3 nM, but did not influence this increase in AVP V1B-receptor expressing cells. In contrast, stimulation of COS-1 cells expressing AVP V2 receptors resulted in an accumulation of cAMP. YM087 inhibited AVP-induced cAMP production in COS-1 cells expressing AVP V2 receptors in a concentration-dependent manner with an IC50 value of 1.95 nM. In all assays used, YM087 was devoid of any agonistic activity. These results suggest that YM087 is a potent nonpeptide dual human AVP V1A and V2 receptor antagonist, and that YM087 will be a powerful tool in investigation of the physiological and pathophysiological roles of AVP.

Pharmacological and pharmacokinetic characteristics of YM435, a novel dopamine DA1-receptor agonist, in anaesthetized dogs.

Time-course of plasma concentration of unchanged drug of the dopamine DA1-receptor agonist (-)-(S)-4-(3,4-dihydroxyphenyl)-7,8-dihydroxy-1,2,3,4- tetrahydroisoquinoline hydrochloride hydrate (YM435), and its effects on blood pressure and renal blood flow were investigated in anaesthetized dogs. Continuous intravenous infusion of YM435 (0.1-3 micrograms kg-1 min-1) rapidly increased renal blood flow and lowered blood pressure in a dose-dependent manner. These effects remained generally stable throughout the infusion period. Following the start of infusion, plasma concentration of unchanged drug also rose rapidly and dose-dependently and remained virtually constant throughout the infusion period. A significant correlation was observed between log YM435 plasma concentration and the increase in renal blood flow (r = 0.93, P < 0.0001) and between the former and the reduction in blood pressure (r = 0.93, P < 0.0001). The present results indicate that YM435 produces renal vasodilatation and lowering of blood pressure in a dose-dependent manner and with rapid onset following continuous intravenous infusion, and that these effects are generally stable throughout the period of infusion. These haemodynamic effects of YM435 were in good agreement with the time-course of plasma concentration of unchanged drug.

Isolation, characterization, and quantitative measurement of serum alpha 1-acid glycoprotein in cattle.

Bovine alpha 1-acid glycoprotein (alpha 1AG) was purified from pooled normal bovine sera by successive ammonium sulfate precipitation, ion-exchange chromatographies and gel filtration. Bovine alpha 1AG had a molecular weight of 42,000 +/- 2,000 and a sedimentation coefficient of 3.4S. It contained 26.6% carbohydrate. Gel isoelectric focusing revealed a microheterogeneity with 7 to 8 bands in a pI range of 3.2 to 3.7. It migrated to the alpha 1-globulin region upon immunoelectrophoresis. Single radial immunodiffusion was developed for the quantitative measurement of bovine alpha 1AG in serum. The mean serum value of alpha 1AG in 152 healthy Holstein cattle (1-12 years old) was 283.2 +/- 82.3 micrograms/ml. Elevated values (cut-off value = 450 micrograms/ml) were observed in cattle with traumatic pericarditis (100%), arthritis (100%), mastitis (91%), pneumonia (70%), and mesenteric liponecrosis (43%).

Norepinephrine release is increased in the hibernating heart, studied in a chronic canine model of myocardial hibernation.

We examined the change in cardiac sympathetic function in the hibernating heart. To induce hibernating hearts in dogs, we placed a nylon tube via the carotid artery in the left circumflex artery (LCx) and obstructed the LCx flow. The plasma norepinephrine (NE) and epinephrine (E) concentrations in the coronary sinus and the aorta were measured before and 1 week after the tube placement to evaluate the catecholamine release from the heart. The wall motion was followed by echocardiography and. 1 week after the tube placement, regional myocardial blood flow (RBF) was measured using colored microspheres. Also. the restorability of myocardial dysfunction was examined in other dogs by extracting the LCx tube 1 week after the placement. Finally, the heart was removed for pathological observation and dogs showing myocardial infarction were excluded. One week after placing the tube, wall thickening was reduced in the LCx area, but was not in the left anterior descending (LAD) area. Compared with the LAD area, RBF in the LCx area was decreased in the endocardium (p < 0.05), but was not in the epicardium. In other dogs, the reduced wall thickening in the LCx area was restored to normal levels 1 or 2 weeks after the tube extraction. Thereby, our dogs with the tube placed were considered to be models of myocardial hibernation. The plasma NE and E concentrations were not significantly changed by placing the tube, but NE release from the heart was increased after the tube placement (p < 0.05). E uptake from the heart did not differ. Therefore, it is suggested that NE release is increased in the hibernating heart and may contribute to its mechanism.

Nonpeptide arginine vasopressin antagonists for both V1A and V2 receptors: synthesis and pharmacological properties of 2-phenyl-4'-[(2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl)carbonyl]benzanil ide derivatives.

A series of compounds structurally related to 4'-[(2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl)carbonyl]benzanili de was synthesized and demonstrated to have arginine vasopressin (AVP) antagonist activity for both V1A and V2 receptors. The introduction of a phenyl or a 4-substituted phenyl group into the ortho position of the benzoyl moiety resulted in an increase in both binding affinity and antagonistic activity. The 2-(4-methylphenyl) derivative (1g) exhibited high antagonistic activities for both V1A (8.6-fold) and V2 (38-fold) receptors and high oral activity (8.6-fold) compared with the 2-methyl lead compound (1a). Detail of the synthesis and the pharmacological properties of this series are presented.

Effect of forskolin on prostaglandin productions in isolated dog renal arteries.

Forskolin (1 to 100 microM), a direct activator of adenylate cyclase, did not have any effect on prostaglandin E2 and I2 productions in isolated dog renal arteries. However, forskolin at the lower concentrations (10 and 100 nM) markedly stimulated only prostaglandin E2 production. 8-Bromo-cyclic AMP (0.5 and 1 mM) failed to stimulate prostaglandin E2 and I2 productions. The results suggest that 1) forskolin stimulates only prostaglandin E2 production, not through the activation of adenylate cyclase and 2) the prostaglandin production system may be independent of the cyclic AMP-generating system in isolated dog renal arteries.

4-(3,4-Dihydroxyphenyl)-1,2,3,4-tetrahydroisoquinoline derivatives. II. Their renal vasodilation activity and structure-activity relationship.

A series of 4-(3,4-dihydroxyphenyl)-1,2,3,4-tetrahydroisoquinoline derivatives showed potent DA1 agonistic activities. We investigated the structure-activity relationship of the racemic compounds of this series. 4-(3,4-Dihydroxyphenyl)-7-methanesulfonamido-1,2,3,4-tetrahydroiso quinoline (43) was identified as a potent renal vasodilator with activity almost equal to that of YM435 (1).

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.