Distinct properties of telmisartan on agonistic activities for peroxisome proliferator-activated receptor γ among clinically used angiotensin II receptor blockers: drug-target interaction analyses.

A proportion of angiotensin II type 1 receptor blockers (ARBs) improves glucose dyshomeostasis and insulin resistance in a clinical setting. Of these ARBs, telmisartan has the unique property of being a partial agonist for peroxisome proliferator-activated receptor γ (PPARγ). However, the detailed mechanism of how telmisartan acts on PPARγ and exerts its insulin-sensitizing effect is poorly understood. In this context, we investigated the agonistic activity of a variety of clinically available ARBs on PPARγ using isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) system. Based on physicochemical data, we then reevaluated the metabolically beneficial effects of telmisartan in cultured murine adipocytes. ITC and SPR assays demonstrated that telmisartan exhibited the highest affinity of the ARBs tested. Distribution coefficient and parallel artificial membrane permeability assays were used to assess lipophilicity and cell permeability, for which telmisartan exhibited the highest levels of both. We next examined the effect of each ARB on insulin-mediated glucose metabolism in 3T3-L1 preadipocytes. To investigate the impact on adipogenesis, 3T3-L1 preadipocytes were differentiated with each ARB in addition to standard inducers of differentiation for adipogenesis. Telmisartan dose-dependently facilitated adipogenesis and markedly augmented the mRNA expression of adipocyte fatty acid-binding protein (aP2), accompanied by an increase in the uptake of 2-deoxyglucose and protein expression of glucose transporter 4 (GLUT4). In contrast, other ARBs showed only marginal effects in these experiments. In accordance with its highest affinity of binding for PPARγ as well as the highest cell permeability, telmisartan superbly activates PPARγ among the ARBs tested, thereby providing a fresh avenue for treating hypertensive patients with metabolic derangement.

Downregulation of vasopressin V1A receptors and activation of mitogen-activated protein kinase in rat mesangial cells cultured under high-glucose conditions.

SUMMARY: In the present study we examined the effects of high extracellular glucose concentrations on vasopressin (AVP) V(1A) receptor kinetics and signal transduction in cultured rat mesangial cells. Scatchard analysis of [(3) H]-AVP binding to mesangial cell plasma membranes showed that although high glucose (30 mmol/L) decreased V(1A) receptor numbers relative to cells cultured in normal glucose (10 mmol/L), receptor affinity was not affected. This V(1A) receptor downregulation was associated with an attenuated increase in AVP-stimulated cytosolic free calcium concentrations ([Ca(2+) ](i) ). In addition, high glucose increased both the basal and AVP-stimulated activity of the classic mitogen-activated protein kinase, namely extracellular signal-regulated kinase (ERK). Furthermore, high glucose induced activation of protein kinase C (PKC) in mesangial cells that could be inhibited by coincubation with the PKC inhibitor staurosporine (10 nmol/L). Staurosporine also markedly attenuated the high glucose-induced downregulation of V(1A) receptors on mesangial cells and blocked the depressed [Ca(2+) ](i) response and increased ERK activity induced by AVP. The results indicate that high extracellular glucose downregulates V(1A) receptors on rat mesangial cells and modulates their signal transduction properties via PKC activation.

Effects of high glucose on AVP-induced hyperplasia, hypertrophy, and type IV collagen synthesis in cultured rat mesangial cells.

INTRODUCTION: Hyperglycemia is a principal characteristic of diabetes and influences many cellular functions. Diabetic nephropathy is characterized by glomerular mesangial expansion which could result from increased mesangial cell extracellular matrix synthesis induced by hyperglycemia. METHODS: To investigate whether the physiological functions of mesangial cells are altered in a diabetic environment, we evaluated the effect of high extracellular glucose concentration on thymidine/leucine incorporation, hyperplasia/hypertrophy, and type IV collagen synthesis, induced by vasopressin (AVP), in cultured rat mesangial cells. RESULTS: The exposure of mesangial cells to a high glucose concentration (30 mM) significantly reduced AVP-induced thymidine incorporation and hyperplasia compared with normal glucose (10 mM). By contrast, treatment of mesangial cells with AVP in the presence of high extracellular glucose significantly increased leucine incorporation, hypertrophy, and type IV collagen synthesis compared with those at normal glucose levels. The administration of staurosporine, a protein kinase C inhibitor, reversed these effects of high-glucose conditions. Furthermore, the nonpeptide AVP V(1A) receptor-selective antagonists potently inhibited these AVP-induced physiological responses in mesangial cells cultured in high-glucose conditions. CONCLUSIONS: These results demonstrate that high glucose suppresses mesangial cell proliferation but enhances hypertrophy and type IV collagen synthesis induced by AVP. This increased mesangial cell hypertrophy and extracellular matrix synthesis may play a crucial role in the glomerular mesangial expansion common to diabetic nephropathy.

Synthesis and pharmacological evaluation of 2-(1-alkylpiperidin-4-yl)-n-[(1r)-1-(4-fluorophenyl)-2-methylpropyl]acetamide Derivatives as Novel Antihypertensive Agents.

We synthesized and evaluated the inhibitory activity of a series of 2-(1-alkylpiperidin-4-yl)-N-[(1R)-1-(4-fluorophenyl)-2-methylpropyl]acetamide derivatives against T-type Ca(2+) channels. Structure-activity relationship studies revealed that the position of the amide structure was important for the potent inhibitory activity toward T-type Ca(2+) channels. In addition, the introduction of an appropriate substituent on the pendant benzene ring played a crucial role for the selectivity towards T-type Ca(2+) channels over L-type Ca(2+) channels and the potent bradycardic activity of these derivatives. Oral administration of N-[(1R)-1-(4-fluorophenyl)-2-methylpropyl]-2-(1-{2-[2-(2-methoxyethoxy)phenyl]ethyl}piperidin-4-yl)acetamide (4f), which had superior selectivity for T-type Ca(2+) channels over L-type Ca(2+) channels, lowered blood pressure in spontaneously hypertensive rats without inducing reflex tachycardia, which is often caused by traditional L-type Ca(2+) channel blockers.

Antifibrotic effects of pirfenidone in rat proximal tubular epithelial cells.

OBJECTIVE: Renal fibrosis is a common cause of renal dysfunction with chronic kidney disease. We previously investigated the renoprotective effects of the antifibrotic agent pirfenidone in a rat model of subtotal nephrectomy. Here, we further evaluated the antifibrotic effects of pirfenidone in rat proximal tubular epithelial cells. METHODS: NRK52E cells were incubated in a medium containing either transforming growth factor (TGF)-ß1 (3 ng/mL) or platelet-derived growth factor (PDGF)-BB (5 Ang/mL) or both, with or without pirfenidone (0.1-1 mmol/L), for 24 h to assess mRNA expression, for 48 h to assess protein production, and for 1 h or various time (5-120 min) to assess phosphorylation of signal kinase. RESULTS: TGF-ß1, a key mediator in renal fibrosis, induced increases in the mRNA expression of various profibrotic factors and extracellular matrix, including plasminogen activator inhibitor type 1 (PAI-1), fibronectin, type 1 collagen, and connective tissue growth factor (CTGF)-increases which pirfenidone significantly inhibited. Specifically, pirfenidone potently inhibited TGF-ß1-induced increases in the mRNA expression and protein secretion of PAI-1, an effect mediated, at least in part, via the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling. Further, PDGF-BB, which has been implicated in renal interstitial fibrosis, potently activated PAI-1 expression under TGF-ß1 stimulation, and pirfenidone significantly inhibited TGF-ß1- and PDGF-BB-induced increases in PAI-1 expression. CONCLUSIONS: Taken together, these results suggest that TGF-ß1 closely correlates with renal fibrosis in cooperation with several fibrosis-promoting molecules, such as PAI-1 and PDGF, in rat proximal tubular epithelial cells, and pirfenidone inhibits TGF-ß1-induced fibrosis cascade and will therefore likely exert antifibrotic effects under pathological conditions.

Synthesis and pharmacological evaluation of 1-alkyl-N-[2-ethyl-2-(4-fluorophenyl)butyl]piperidine-4-carboxamide derivatives as novel antihypertensive agents.

We synthesized and evaluated inhibitory activity against T-type Ca(2+) channels for a series of 1-alkyl-N-[2-ethyl-2-(4-fluorophenyl)butyl]piperidine-4-carboxamide derivatives. Structure-activity relationship studies have revealed that dialkyl substituents at the benzylic position play an important role in increasing inhibitory activity. Oral administration of N-[2-ethyl-2-(4-fluorophenyl)butyl]-1-(2-phenylethyl)piperidine-4-carboxamide (20d) lowered blood pressure in spontaneously hypertensive rats without inducing reflex tachycardia, which is often caused by traditional L-type Ca(2+) channel blockers.

Synthesis and pharmacological evaluation of 1-isopropyl-1,2,3,4-tetrahydroisoquinoline derivatives as novel antihypertensive agents.

A series of 1-isopropyl-1,2,3,4-tetrahydroisoquinoline derivatives were synthesized and their bradycardic activities were evaluated in isolated guinea pig right atria. Structure-activity relationship studies revealed that the introduction of an appropriate substituent and its position on the 1,2,3,4-tetrahydroisoquinoline ring are essential for potent in vitro activity. Furthermore, the tether between the piperidyl moiety and the terminal aromatic ring is important for potent antihypertensive activity. Oral administration of 6-fluoro-1-isopropyl-2-{[1-(2-phenylethyl)piperidin-4-yl]carbonyl}-1,2,3,4-tetrahydroisoquinoline (3b) to spontaneously hypertensive rats (SHR) elicited antihypertensive effects without inducing reflex tachycardia, which is often caused by traditional L-type Ca²âº channel blockers.

Synthesis and pharmacological evaluation of 1-alkyl-N-[(1R)-1-(4-fluorophenyl)-2-methylpropyl]piperidine-4-carboxamide derivatives as novel antihypertensive agents.

We synthesized and evaluated inhibitory activity against T-type Ca(2+) channels for a series of 1-alkyl-N-[(1R)-1-(4-fluorophenyl)-2-methylpropyl]piperidine-4-carboxamide derivatives. Structure-activity relationship studies have revealed that the isopropyl substituent at the benzylic position plays an important role in exerting potent inhibitory activity, and the absolute configuration of the benzylic position was found to be opposite that of mibefradil, which was first launched as a new class of T-type Ca(2+) channel blocker. Oral administration of N-[(1R)-1-(4-fluorophenyl)-2-methylpropyl]-1-[2-(3-methoxyphenyl)ethyl]piperidine-4-carboxamide (17f) lowered blood pressure in spontaneously hypertensive rats without inducing reflex tachycardia, an adverse effect often caused by traditional L-type Ca(2+) channel blockers.

Therapeutic effects of interleukin-1 receptor-associated kinase 4 inhibitor AS2444697 on diabetic nephropathy in type 2 diabetic mice.

Renal inflammation is a final common pathway of chronic kidney disease including diabetic nephropathy, which is the leading cause of end-stage renal disease and is associated with high cardiovascular risk and significant morbidity and mortality. Interleukin-1 (IL-1) receptor-associated kinase 4 (IRAK-4) is a pivotal molecule for IL-1 receptor- and Toll-like receptor-induced activation of proinflammatory mediators. In this study, we investigated the renoprotective properties of IRAK-4 inhibitor AS2444697 in KK/Ay type 2 diabetic mice. Four-week repeated administration of AS2444697 dose-dependently and significantly improved albuminuria; hyperfiltration, as measured by creatinine clearance; renal injury, including glomerulosclerosis; tubular injury markers, including urinary N-acetyl-ß-D-glucosaminidase activity; and glomerular podocyte injury markers, including urinary nephrin excretion. In addition, AS2444697 attenuated plasma levels of proinflammatory cytokines, including IL-6; plasma levels of endothelial dysfunction markers, including intercellular adhesion molecule-1; and plasma levels and renal contents of oxidative stress markers. In contrast, AS2444697 did not significantly affect food intake or blood glucose levels. These results suggest that AS2444697 attenuates the progression of diabetic nephropathy mainly via anti-inflammatory mechanisms through inhibition of IRAK-4 activity under diabetic conditions and may represent a promising therapeutic option for the treatment of type 2 diabetic nephropathy.

Effect of vasopressin on type IV collagen production in human mesangial cells.

Production of extracellular matrix proteins, such as type IV collagen and fibronectin, by mesangial cells contributes to progressive glomerulosclerosis. In this study, the ability of vasopressin (AVP), which causes mesangial cell proliferation and hypertrophy, to stimulate type IV collagen production by cultured human mesangial cells was examined using an enzyme-linked immunosorbent assay. AVP induced a concentration-dependent increase in the production of type IV collagen and this effect was potently and concentration-dependently inhibited by AVP V1A receptor antagonists, including YM218. AVP also induced a concentration-dependent increase in transforming growth factor (TGF)-beta secretion by human mesangial cells and this effect was inhibited by V1A receptor antagonists. Furthermore, TGF-beta also induced an increase in the production of type IV collagen; the AVP-enhanced production of type IV collagen was inhibited by an anti-TGF-beta antibody. These findings indicate that AVP stimulates synthesis of type IV collagen by cultured human mesangial cells through the induction of TGF-beta synthesis mediated by V1A receptors; consequently, AVP contributes to glomerular remodeling and extracellular matrix accumulation observed in glomerular diseases.

Vasopressin stimulates the production of extracellular matrix by cultured rat mesangial cells.

1. Mesangial expansion, an indicator of chronic glomerular diseases, occurs as a result of the excessive accumulation of extracellular matrix (ECM) proteins, such as type IV collagen. In order to investigate the ability of vasopressin (AVP), which causes mesangial cell proliferation and hypertrophy, to induce ECM production, an enzyme-linked immunosorbent assay was used to measure type I and IV collagen and fibronectin produced from cultured rat mesangial cells. 2. Addition of AVP (0.01-1000 nmol/L) caused a significant and concentration-dependent production of secreted and cell-associated ECM, type I collagen, type IV collagen and fibronectin by cultured rat mesangial cells. The AVP V(1A) receptor-selective antagonist YM218 (0.01-1000 nmol/L) potently and concentration-dependently inhibited the induced increase in ECM production caused by AVP, but the V(2) receptor-selective antagonist SR 121463A (0.1-1000 nmol/L) did not potently inhibit. 3. Vasopressin inhibited the synthesis of matrix metalloproteinase (MMP)-2, which degrades matrix proteins, including type IV collagen, and stimulated endothelin (ET)-1 secretion from mesangial cells. These effects were potently inhibited by YM218, but not by SR 121463A. 4. In addition, 10 nmol/L ET-1 inhibited the synthesis of MMP-2 and stimulated ECM production in mesangial cells. These effects were completely abolished by the ET(A) receptor-selective antagonist YM598 (1 micromol/L); however, the ET(B) receptor-selective antagonist BQ-788 (1 micromol/L) and the AVP receptor antagonists YM218 and SR 121463A did not inhibit ET-1-induced inhibition of MMP-2 synthesis and ECM production. In addition, AVP-induced inhibition of MMP-2 synthesis and ECM production were partly inhibited by YM598. 5. These findings indicate that AVP may modulate ECM production not only via a direct action on V(1A) receptors, but also through stimulation of ET-1 secretion. Vasopressin may contribute to the glomerular remodelling and ECM accumulation observed in glomerular diseases.

Effect of YM218, a nonpeptide vasopressin V(1A) receptor-selective antagonist, on rat mesangial cell hyperplasia and hypertrophy.

Mesangial cell growth constitutes a key feature of progressive glomerular injury. Vasopressin (AVP), a potent peptide vasoconstrictor, acts on mesangial cells through the V(1A) receptors, inducing contraction and cell proliferation. This study examined the effects of YM218, a nonpeptide AVP V(1A) receptor-selective antagonist, on the mitogenic and hypertrophic effects of AVP in rat mesangial cells. When added to mesangial cells whose growth was arrested, AVP concentration-dependently induced hyperplasia and hypertrophy. YM218 potently prevented AVP-induced hyperplasia and hypertrophy of these cells. Furthermore, AVP stimulated endothelin (ET)-1 secretion from mesangial cells in a concentration-dependent manner and this effect was potently inhibited by YM218. ET-1 also induced hyperplasia and hypertrophy in mesangial cells and this effect was completely abolished by ET(A) receptor-selective antagonist YM598. In addition, AVP-induced hyperplasia and hypertrophy were partly inhibited by YM598. These results suggest that AVP may modulate mesangial cell growth not only by its direct action but also through the stimulation of ET-1 secretion. YM218 displays high potency in inhibiting the AVP-induced physiologic responses of mesangial cells via the V(1A) receptors and is a potent pharmacologic probe for investigating the physiologic and pathophysiologic roles of AVP in several renal diseases.

Effects of YM218, a nonpeptide vasopressin V(1A) receptor-selective antagonist, on vasopressin-induced growth responses in human mesangial cells.

Mesangial cells are centrally-located glomerular pericytes with contractile, endocrine, and immunity-regulating functions. These cells are thought to maintain normal glomerular function, since mesangial cell proliferation and extracellular matrix formation are hallmarks of chronic glomerular disease. Vasopressin causes mesangial cell contraction, proliferation and hypertrophy. Consequently, the effects of YM218, a potent, nonpeptide vasopressin V(1A) receptor-selective antagonist, on the growth responses of human mesangial cells to vasopressin were investigated. YM218 showed high affinity for vasopressin V(1A) receptors, exhibiting a K(i) value of 0.18 nM. Vasopressin concentration-dependently increased intracellular Ca(2+) levels and induced hyperplasia and hypertrophy in cultured mesangial cells, YM218 potently inhibited these vasopressin-induced responses. These results clearly show that YM218 has both strong affinity for human mesangial cell vasopressin V(1A) receptors and great potency in inhibiting the vasopressin-induced growth responses of mesangial cells controlled by the vasopressin V(1A) receptors. The hyperplasia and hypertrophy of mesangial cells in vitro caused by vasopressin indicate its possible in vivo role in glomerular disease pathogenesis. Therefore, YM218 is a potent pharmacologic probe to investigate the physiologic and pathophysiologic roles of vasopressin in the development of renal disease.

Effect of YM-254890, a specific Galphaq/11 inhibitor, on experimental peripheral arterial disease in rats.

The protective effect of YM-254890, a specific Galphaq/11 inhibitor, on laurate-induced peripheral arterial disease in rats was compared with those of prostaglandin E1 (PGE1), beraprost, and clopidogrel. YM-254890 inhibited ADP-induced ex vivo rat platelet aggregation at a dose of 3 microg/kg. Furthermore, YM-254890 strongly inhibited phenylephrine-, serotonin- and endothelin-1-induced contractions in the rat aorta, and improved dermal blood flow after the laurate injection. The intra-arterial single bolus administration of YM-254890 15 min after the laurate injection dose-dependently inhibited the progression of the lesion, with significance, at 3 microg/kg without affecting systemic blood pressure. PGE1 and beraprost, when administered before the laurate injection, were effective, but their potencies were less than that of YM-254890. Clopidogrel significantly suppressed lesion progression when administered at 30 mg/kg twice a day for 3 days, which completely inhibited platelet aggregation. These results suggest that the local administration of YM-254890 may be useful for treating peripheral arterial disease.

Original Research: Potential of urinary nephrin as a biomarker reflecting podocyte dysfunction in various kidney disease models.

Urinary nephrin is a potential non-invasive biomarker of disease. To date, however, most studies of urinary nephrin have been conducted in animal models of diabetic nephropathy, and correlations between urinary nephrin-to-creatinine ratio and other parameters have yet to be evaluated in animal models or patients of kidney disease with podocyte dysfunction. We hypothesized that urinary nephrin-to-creatinine ratio can be up-regulated and is negatively correlated with renal nephrin mRNA levels in animal models of kidney disease, and that increased urinary nephrin-to-creatinine ratio levels are attenuated following administration of glucocorticoids. In the present study, renal nephrin mRNA, urinary nephrin-to-creatinine ratio, urinary protein-to-creatinine ratio, and creatinine clearance ratio were measured in animal models of adriamycin nephropathy, puromycin aminonucleoside nephropathy, anti-glomerular basement membrane glomerulonephritis, and 5/6 nephrectomy. The effects of prednisolone on urinary nephrin-to-creatinine ratio and other parameters in puromycin aminonucleoside (single injection) nephropathy rats were also investigated. In all models tested, urinary nephrin-to-creatinine ratio and urinary protein-to-creatinine ratio increased, while renal nephrin mRNA and creatinine clearance ratio decreased. Urinary nephrin-to-creatinine ratio exhibited a significant negative correlation with renal nephrin mRNA in almost all models, as well as a significant positive correlation with urinary protein-to-creatinine ratio and a significant negative correlation with creatinine clearance ratio. Urinary protein-to-creatinine ratio exhibited a significant negative correlation with renal nephrin mRNA. Following the administration of prednisolone to puromycin aminonucleoside (single injection) nephropathy rats, urinary nephrin-to-creatinine ratio was significantly suppressed and exhibited a significant positive correlation with urinary protein-to-creatinine ratio. In addition, the decrease in number of glomerular Wilms tumor antigen-1-positive cells was attenuated, and urinary nephrin-to-creatinine ratio exhibited a significant negative correlation in these cells. In conclusion, these results suggest that urinary nephrin-to-creatinine ratio level is a useful and reliable biomarker for predicting the amelioration of podocyte dysfunction by candidate drugs in various kidney disease models with podocyte dysfunction. This suggestion will also be validated in a clinical setting in future studies.

Pharmacologic properties of YM218, a novel, potent, nonpeptide vasopressin V1A receptor-selective antagonist.

The pharmacologic profile of YM218, (Z)-4'-{4,4-difluoro-5-[2-oxo-2-(4-piperidinopiperidino)ethylidene]-2,3,4,5-tetrahydro-1H-1-benzoazepine-1-carbonyl}-2-methyl-3-furanilide hemifumarate, a newly synthesized, nonpeptide vasopressin (AVP) receptor antagonist, was investigated using several in vitro and in vivo methods. YM218 exhibited high affinity for V1A receptors isolated from rat liver, with a Ki value of 0.50 nM. In contrast, YM218 exhibited much lower affinity for rat pituitary V1B, kidney V2, and uterus oxytocin receptors, with Ki values of 1510 nM, 72.2 nM, and 150 nM, respectively. In vivo studies revealed that YM218 dose-dependently inhibited pressor response to exogenous AVP in pithed rats (intravenous) and in conscious normotensive rats (intravenous or oral) with a long duration of action (>8 h at 3 mg/kg, p.o.). In contrast, oral administration of YM218 did not increase urine excretion in conscious rats. These results demonstrate that YM218 is a potent nonpeptide AVP V1A receptor-selective antagonist that will be useful in future studies to help clarify the physiologic and pathophysiologic roles of AVP.

Effect of YM471, an orally active non-peptide arginine vasopressin receptor antagonist, on human vascular smooth muscle cells.

OBJECTIVE: To investigate the effects of YM471, a non-peptide arginine vasopressin (AVP) V1A and V2 receptor antagonist, on the AVP-induced growth responses in human vascular smooth muscle cells (VSMCs). METHODS: Binding of YM471 to V1A receptors on VSMCs was measured using [3H]AVP. Intracellular free Ca2+ concentration was measured by fura 2 fluorescence. Mitogen-activated protein (MAP) kinase activity was determined using the p42/p44 MAP kinase specific peptide and [gamma- 32P]ATP as substrates. The effect of AVP on hyperplasia and hypertrophy of VSMCs was determined by cell number and protein content measurements. RESULTS: YM471 potently and concentration-dependently inhibited the specific binding of [ 3H]AVP to V1A receptors on VSMCs, exhibiting an inhibition constant (Ki ) of 0.35 nmol/l. YM471 inhibited the AVP-induced increase in intracellular free Ca concentration with an 50% inhibition concentration (IC50 ) of 2.01 nmol/l and inhibited the activation of MAP kinase with an IC50 of 6.11 nmol/l. In addition, AVP concentration-dependently induced hyperplasia and hypertrophy in VSMCs, but YM471 prevented these AVP-induced growth effects, exhibiting IC50 values of 2.31 and 0.23 nmol/l, respectively. CONCLUSIONS: These results indicate that YM471 has high affinity for V receptors on, and potently inhibits AVP-induced physiologic responses of, human VSMCs.

Effect of YM471, a nonpeptide AVP receptor antagonist, on human coronary artery smooth muscle cells.

The antagonistic properties of YM471, a potent nonpeptide vasopressin (AVP) V(1A) and V(2) receptor antagonist, were characterized using human coronary artery smooth muscle cells (CASMC). YM471 potently inhibited specific binding of 3H-AVP to V(1A) receptors on human CASMC, exhibiting a K(i) value of 0.49 nM. Furthermore, YM471 inhibited the AVP-induced increase in intracellular free Ca(2+) concentration with an IC(50) value of 1.42 nM, but exerted no agonistic activity on CASMC. Additionally, while AVP concentration-dependently induced hyperplasia and hypertrophy in CASMC, YM471 prevented these AVP-induced growth effects, exhibiting IC(50) values of 0.93 and 2.64 nM, respectively. These results indicate that YM471 has high affinity for V(1A) receptors on, and high potency in inhibiting AVP-induced physiologic responses of, human CASMC.

Effect of the vasopressin receptor antagonist conivaptan in rats with heart failure following myocardial infarction.

Myocardial infarction often induces congestive heart failure accompanied by a significant increase in plasma vasopressin concentration. To delineate the role of vasopressin in the pathogenesis of congestive heart failure, the acute hemodynamic and aquaretic effects of conivaptan (YM087, 4'-(2-methyl-1,4,5,6-tetrahydroimidazo[4,5-d][1]benzoazepine-6-carbonyl)-2-phenylbenzanilide monohydrochloride), a combined vasopressin V(1A) and V(2) receptor antagonist, were assessed in rats with heart failure induced by myocardial infarction. Left coronary artery ligation resulted in decreased left ventricular systolic pressure and first derivatives of left ventricular developed pressure, as well as increased left ventricular end-diastolic pressure, lung and right ventricular weight. Single oral administration of conivaptan (0.3 to 3.0 mg/kg) dose-dependently increased urine volume and decreased urine osmolality in heart failure rats. Furthermore, conivaptan (3.0 mg/kg) attenuated the changes in left ventricular end-diastolic pressure, lung and right ventricular weight induced by heart failure while reducing blood pressure. These results show that vasopressin plays a significant role in elevating vascular tone through vasopressin V(1A) receptors and plays a major role in retaining free water through vasopressin V(2) receptors in this model of congestive heart failure. Additionally, conivaptan, with its dual vasopressin V(1A) and V(2) receptor-inhibiting properties, could exert a beneficial effect on cardiac function in the congestive heart failure rat model.

Pharmacological characterization of YM471, a novel potent vasopressin V(1A) and V(2) receptor antagonist.

The pharmacologic profile of 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), a novel potent vasopressin V(1A) and V(2) receptor antagonist, was investigated using several in vitro and in vivo techniques. YM471 showed high affinity for rat vasopressin V(1A) and V(2) receptors, exhibiting K(i) values of 0.16 and 0.77 nM, respectively. In contrast, YM471 exhibited much lower affinity for rat vasopressin V(1B) and oxytocin receptors, with K(i) values of 10.5 microM and 31.0 nM, respectively. In conscious rats, oral administration of YM471 (0.1-3.0 mg/kg) produced dose-dependent inhibition of the pressor response caused by exogenous vasopressin and increased urine excretion and decreased urine osmolality; this effect lasted more than 8 h. In all biological assays used, YM471 exhibited no agonistic activity. These results demonstrate that YM471 exerts potent and long-lasting antagonistic activity on both vasopressin V(1A) and V(2) receptors, and that this compound may be a useful tool for clarifying the physiologic and pathophysiologic roles of vasopressin and the therapeutic usefulness of the vasopressin receptor antagonist.