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 structure-activity relationships of amide derivatives of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetic acid as selective arginine vasopressin V2 receptor agonists.

A series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetamide derivatives was synthesized, and their structure-activity relationships were examined in order to identify potent and selective arginine vasopressin V(2) receptor agonists. Attempts to substitute other chemical groups in place of the 2-pyridilmethyl moiety of 1a led to the discovery that potent V(2) binding affinity could be obtained with a wide range of functional groups. This structural tolerance allowed for the manipulation of other attributes, such as selectivity against V(1a) receptor affinity or avoidance of the undesirable inhibition of cytochrome P450 (CYP), without losing potent affinity for the V(2) receptor. Some representative compounds obtained in this study were also found to decrease urine volume in awake rats.

Optimization of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives as arginine vasopressin V2 receptor agonists and discussion of their binding modes.

A series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives were optimized to achieve potent agonistic activity, both in vitro and in vivo, for the arginine vasopressin V(2) receptor, resulting in the eventual discovery of compound 1g. Molecular modeling of compound 1g with V(2) receptor was also examined to evaluate the binding mode of this series of compounds.

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.

Preparation of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetamide derivatives as novel arginine vasopressin V(2) receptor agonists.

The present work describes the discovery of novel series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives as arginine vasopressin (AVP) V(2) receptor agonists. By replacing the amide juncture in YM-35278 with a direct ring connection gave compound 10a, which acts as a V(2) receptor agonist. These studies provided the potent, orally active non-peptidic V(2) receptor agonists 10a and 10j.

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 zelandopam, a dopamine D1-like receptor agonist, in puromycin aminonucleoside nephrosis rats.

The present experiment was designed to investigate the role of peripheral dopamine D1-like receptors and to evaluate the prophylactic effect of zelandopam, a dopamine D1-like receptor agonist, on puromycin aminonucleoside (PA)-induced nephrosis in rats. Rats were divided into six groups (n=10 per group): 0.9% saline-injected rats (control); PA-injected rats (PAN); PA-injected rats treated with the selective dopamine D1-like receptor agonist zelandopam (30, 100, 300 mg/kg p.o. twice a day); PA-injected rats treated with prednisolone (1 mg/kg p.o. once a day). Nephrosis was induced in rats with a single intravenous injection of PA at a dose of 50 mg/kg. The effects of zelandopam and prednisolone in PA nephrosis rats were evaluated before injection of PA and at 7 and 14 days after injection. PA-induced nephrosis was characterized by an increase in urinary protein excretion (proteinuria) and plasma total cholesterol. Zelandopam dose-dependently attenuated the increase in proteinuria and total cholesterol. Prednisolone significantly attenuated the increase in proteinuria and total cholesterol and resulted in a significant decrease in body weight. The present study demonstrates for the first time that zelandopam, a selective dopamine D1-like receptor agonist, is effective in blunting the development of PA-induced nephrosis, and that the effects of zelandopam are dose dependent.

Intravenous administration of conivaptan hydrochloride improves cardiac hemodynamics in rats with myocardial infarction-induced congestive heart failure.

We investigated the effects of intravenously administered conivaptan hydrochloride, a dual vasopressin V1A and V2 receptor antagonist, on cardiac function in rats with congestive heart failure following myocardial infarction, and compared results with those for the selective vasopressin V2 receptor antagonist SR121463A. Rats were subjected to left coronary artery occlusion to induce myocardial infarction, which in turn led to congestive heart failure. At 4 weeks after coronary occlusion, conivaptan (0.03, 0.1 and 0.3 mg/kg i.v.) dose-dependently increased urine volume and reduced urine osmolality in both myocardial infarction and sham-operated rats. SR121463A (0.3 mg/kg i.v.) also increased urine volume and decreased urine osmolality in myocardial infarction rats, to a degree comparable to that by conivaptan (0.3 mg/kg i.v.). At 6 weeks after surgery, myocardial infarction rats showed increases in right ventricular systolic pressure, right atrial pressure, left ventricular end-diastolic pressure and relative weights of the heart and the lungs, and a decrease in first derivative of left ventricular pressure (dP/dt(max))/left ventricular pressure, showing that congestive heart failure was well established. Conivaptan (0.3 mg/kg i.v.) significantly reduced right ventricular systolic pressure, left ventricular end-diastolic pressure, lung/body weight and right atrial pressure in myocardial infarction rats. Moreover, conivaptan (0.3 mg/kg i.v.) significantly increased dP/dt(max)/left ventricular pressure. SR121463A at a dose of 0.3 mg/kg i.v. significantly decreased left ventricular end-diastolic pressure and right atrial pressure, and tended to decrease right ventricular systolic pressure and relative lung weight in myocardial infarction rats. Although the aquaretic and preload-reducing effects of SR121463A were similar to those of conivaptan, SR121463A failed to improve dP/dt(max)/left ventricular pressure. These results suggest that dual vasopressin V1A and V2 receptor antagonists provide greater benefit than selective vasopressin V2 receptor antagonists in the treatment of congestive heart failure.

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.

Preventive effect of zelandopam, a dopamine D1 receptor agonist, on cisplatin-induced acute renal failure in rats.

To elucidate the role of peripheral dopamine D1 receptors in cisplatin-induced acute renal injury, effect of zelandopam (YM435, (-)-(S)-4-(3,4-dihydroxyphenyl)-7,8-dihydroxy-1,2,3,4-tetrahydroisoquinoline hydrochloride hydrate), a selective renal dopamine D1 receptor agonist, on cisplatin-induced acute renal failure in rats was studied. Rats were divided into six groups: control, cisplatin and cisplatin plus zelandopam (30, 100, 300 mg/kg p.o. twice, 75 and 15 min before cisplatin injection) or the free radical scavenger CV-3611 (2-O-octadecylascorbic acid, 10 mg/kg p.o., 75 min before cisplatin injection) treated groups. Rats received intraperitoneal injection of cisplatin at a dose of 5 mg/kg. Four days after cisplatin injection, plasma creatinine, blood urea nitrogen and body weight were measured and the kidneys were removed for histological examination. Cisplatin induced acute renal failure characterized by the increases in plasma creatinine and blood urea nitrogen with tubular damage, and decreased body weight. Zelandopam dose-dependently prevented all these changes. The free radical scavenger CV-3611 significantly attenuated a decrease in body weight and renal dysfunction without reducing tubular damage. The present study is the first demonstration for that a selective dopamine D1 receptor agonist is effective in preventing acute renal failure induced by cisplatin.

The role of Ca2+ in the control of renin release from dog renal cortical slices.

Using a continuous superfusion system of dog renal cortical slices, we studied the role of Ca(2+) in the intracellular control mechanism for renin release. The calcium ionophore A23187 (10 microM) produced a significant decrease in renin release. This effect was abolished in the absence of extracellular Ca(2+). Moreover, pretreatment with the calmodulin inhibitor W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, 20 microM) completely prevented the inhibitory effect of A23187 (10 microM). The beta-adrenoceptor agonist isoproterenol (1, 10 and 100 microM) produced a concentration-dependent increase in renin release. Pretreatment with W-7 (20 microM) potentiated the stimulation of renin release induced by isoproterenol (1 microM). These results suggest that A23187-induced inhibition of renin release is mediated by the activation of calmodulin via an increase in intracellular Ca(2+) and beta-adrenoceptor-stimulated renin release is modulated by intracellular Ca(2+) mobilization.

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.

Vasopressin induces human mesangial cell growth via induction of vascular endothelial growth factor secretion.

Vasoactive hormones, growth factors, and cytokines are important in promoting mesangial cell growth, a characteristic feature of many glomerular diseases. Vascular endothelial growth factor (VEGF) is an endothelial mitogen and promoter of vascular permeability that is constitutively expressed in human glomeruli, but its role in the kidney is still unclear. In the present study, we investigated the ability of vasopressin (AVP) to stimulate VEGF secretion by and correlation with AVP-induced cell growth in human mesangial cells. AVP caused time- and concentration-dependent increases in VEGF secretion from human mesangial cells, which was in turn potently inhibited by a V(1A) receptor-selective antagonist, confirming that this secretion is a V(1A) receptor-mediated event. VEGF also induced mesangial cell growth which was completely inhibited on administration of an anti-VEGF neutralizing antibody. Further, AVP-induced mesangial cell growth was completely abolished by the V(1A) receptor-selective antagonist and partially inhibited by an anti-VEGF neutralizing antibody. These results suggest that AVP stimulates VEGF secretion by human mesangial cells via V(1A) receptors. This secreted VEGF may function as an autocrine hormone to regulate mesangial cell growth, a mechanism by which AVP might contribute to progressive glomerular diseases such as diabetic nephropathy.

Vasopressin regulates rat mesangial cell growth by inducing autocrine secretion of vascular endothelial growth factor.

Mesangial cell growth is a key feature of several glomerular diseases. Vascular endothelial growth factor (VEGF) is a potent mitogen of vascular endothelial cells and promoter of vascular permeability. Here, we examined the ability of vasopressin (AVP), which causes mesangial cell proliferation and hypertrophy, to stimulate VEGF secretion from cultured rat mesangial cells. AVP potently induced a time- and concentration-dependent increase in VEGF secretion in these cells, which was then inhibited by a V(1A) receptor-selective antagonist, confirming this is a V(1A) receptor-mediated event. VEGF also induced hyperplasia and hypertrophy in mesangial cells, which was completely abolished by an anti-VEGF antibody. In addition, AVP-induced hyperplasia and hypertrophy were completely inhibited by the V(1A) receptor-selective antagonist and partially abolished by the anti-VEGF antibody. These results indicate that AVP increases VEGF secretion in rat mesangial cells via V(1A) receptors and modulates mesangial cell growth not only by direct action but also through stimulation of VEGF secretion. This autocrine mechanism might contribute to glomerulosclerosis in renal diseases such as diabetic nephropathy.