The mechanism underlying increased AVP synthesis and release in glucocorticoid deficiency is not known. Therefore, the present study was undertaken to investigate whether the mechanism was at the level of AVP gene transcription. The AVP gene promoter contains a consensus GRE, a CRE, and four AP2 sites. To assess the functional importance of these sites, 5′ deletions of the AVP promoter were created and transient transfections were performed. Promoter activity in hypothalamic cells transfected with deletions lacking the GRE or both the GRE and CRE exhibited higher activity when compared to longer constructs containing both sites. In neuroblastoma cells, only the deletion lacking the GRE exhibited increased AVP promoter activity over the longer construct. These results are consistent with the idea that glucocorticoids suppress AVP gene expression by acting on a GRE in the AVP promoter region. Further, dexamethasone inhibited AVP promoter activity by >50% in hypothalamic cells transfected with the GRE-containing construct. In conclusion, the data presented here support a central mechanism to explain, at least in part, the nonosmotic increase in AVP with glucocorticoid deficiency.

Background: Human brain natriuretic peptide (hBNP) is a promising agent for the treatment of decompensated cardiac failure. However, the systemic hemodynamic, neurohormonal, and renal effects of hBNP have been incompletely studied in human heart failure.

Kappa (κ) opioid agonists induce a water diuresis and inhibit vasopressin (AVP) secretion. Hypothalamic and neurohypophysial sites have both been implicated in the response. The present study was designed to ascertain if κ-agonist inhibition of osmotically-stimulated AVP secretion is associated with parallel changes in AVP gene expression. Experiments were performed using the selective κ-agonist RU 51599 (RU) in compartmentalized hypothalamo-neurohypophysial expiants. When added to either the hypothalamus or the neural lobe, RU dose dependently inhibited osmotically-induced AVP secretion that was reversed by the highly selective κ-antagonist nor-binaltorphimine (nor-BNI) only at the hypothalamic, not the neurohypophysial level. AVP mRNA content paralleled the changes in AVP secretory rate induced by hypothalamic κ-agonism. AVP mRNA levels were unaltered when RU was applied to the neural lobe. Neurohypophysial AVP content did not change. These data indicate that hypothalamic κ-agonism inhibits osmotically induced AVP secretion and that a non-κ1 opiate receptor mediates posterior pituitary opioid inhibition of AVP release. Neural or receptor inputs to the hypothalamus or magnocellular cell body may downwardly modulate AVP mRNA content by altering AVP gene transcription and/or message stability. Inhibition of AVP release directly at the neurohypophysis can be uncoupled from the cellular mechanisms that generate changes in AVP mRNA content.

Defects in peptide processing are associated with several disorders, including central diabetes insipidus (CDI). In the Brattleboro (BB) rat with CDI, the mRNA and protein of arginine vasopressin (AVP) are present in the hypothalamus, but no circulating AVP is detectable, thus suggesting a processing defect. The present study examined AVP secretion in cultured COS cells transfected with various constructs from wild-type and mutated Brattleboro AVP gene precursors. The precursor contains three exons encoding for vasopressin (VP), neurophysin (NP), and glycopeptide (GP). The Brattleboro rat has a deletion of a single base, guanine (G), in the NP coding region that leads to a frameshift, resulting in the loss of normal stop codon. The wild-type pcVP (22.0 +/- 5.2 pg/10[-2] U beta-galactosidase [beta-gal]), but not the mutated BB AVP gene pcBB (1.2 +/- 0.4 pg/10[-2] U beta-gal), was associated with AVP secretion from the COS cells as measured by RIA. The wild-type AVP gene without the GP coding region was associated with AVP release greater (47.4 +/- 13.5 pg/10[-2] U beta-gal, n = 5, P < 0.05, versus pcVP) than the pcVP with intact VP, NP, and GP coding regions. However, the wild-type AVP gene with VP coding region alone was not processed and secreted. Normalizing the pcBB total length with the insertion of a stop codon at the site of the normal stop codon was not associated with AVP secretion (3.0 +/- 1.4 pg/10[-2] U beta-gal). However, insertion of a stop codon so that the pcBB length equaled the length of VP and NP coding regions of the wild type was associated with AVP secretion (13.5 +/- 4.0 pg/10[-2] U beta-gal). When a stop codon was inserted into the wild-type NP coding region at the same site as the G deletion in the pcBB, the AVP secretion was significantly lower (15.1 +/- 5.0 pg/10[-2] U beta-gal) than pcVP with VP + NP but no GP coding regions (47.4 +/- 13.5 pg/10[-2] U beta-gal, n = 5, P < 0.05). In summary, (1) both VP and intact NP, but not GP, coding regions are necessary for AVP processing and secretion; (2) decreasing the length of the NP coding region diminishes but does not abolish AVP processing and secretion; and (3) shortening of the pcBB length with a stop codon at a site comparable to wild-type VP + NP allows AVP secretion, albeit less than with wild-type gene precursor. Thus, the CDI in BB rats is caused by the G deletion in NP coding region. This defect leads to abnormalities that contribute to the abnormal AVP processing. Specifically, the frameshift and absence of a stop codon cause a mutated extended C terminus, which, along with the mutated NP, contribute to the abnormal steps of AVP processing, transport, and secretion in the BB rat. These defects no doubt impair the folding and configuration necessary for normal processing of the AVP gene precursor.

Arginine vasopressin (AVP) is synthesized in the magnocellular neurons of the hypothalamus and stored in the posterior pituitary. It has been shown that hypothalamic AVP mRNA is increased during experimental stimulation of osmotic and non-osmotic stimulation of AVP release. The mechanisms underlying the stimulation of AVP biosynthesis in these conditions are not known. The present study was, therefore, performed to measure AVP release, AVP mRNA level, and AVP gene promoter activity during osmotic and non-osmotic stimulation of AVP secretion in the small cell lung carcinoma (SCLC) cells. AVP release was measured by radioimmunoassay, steady state levels of AVP mRNA by solution hybridization, and AVP gene promoter activity exhibited by a 1.5 kb 5′-flanking AVP gene fragment fused to a luciferase reporter after SCLC cells were subjected to osmotic or non-osmotic conditions. High media osmolality (330 mOsm) significantly increased AVP release (control (C) 1.42 ± 0.27 vs. High Osm 3.67 ± 0.39 pg/2 × 106 cells, N = 9, P < 0.002); AVP mRNA (C 173.6 ± 16.8 vs. High Osm 280.1 ± 19.4 pg/2 × 106 cells, N = 7, P < 0.001); and AVP gene promoter activity (C 1353 ± 99 vs. High Osm 2026 ± 134 L.U./10−4 U β-gal, N = 8, P < 0.001). Non-osmotic stimulators, 0.1 μM endothelin 3 (ET3), 1 μM angiotensin II (AII), and 10 μM acetylcholine (Ach) significantly increased AVP release; ET3 (C 1.78 ± 0.20 vs. ET3 6.85 ± 1.86 pg/2 × 106 cells, N = 8, P < 0.02); AII (C 1.29 ± 0.38 vs. AII 27.80 ± 7.09 pg/2 × 106 cells, N = 5, P < 0.05) and Ach (C 1.14 ± 0.33 vs. Ach 2.68 ± 0.58 pg/2 × x106 cells, N = 6, P < 0.05). However, only ET3 significantly increased AVP mRNA (C 166.6 ± 19.6 vs. ET3 254.4 ± 25.6 pg/p × 106 cells, N = 5, P < 0.05) and AVP promoter activity (C 1515 ± 163 vs. ET3 2389 ± 342 L.U./10−4 U β-gal, n = 6, P < 0.05). To localize the region of the AVP promoter that mediates the osmotic stimulation and the effect of ET3, 5′ deletions of the AVP promoter fragments terminating at −532, −211, and −102, was assessed. Only the promoter activity of the 1.5 kb construct, but not the delection constructs, was significantly increased by ET3 or high osmolality. These results suggest that modulation of AVP gene transcription is, at least in part, responsible for increased AVP synthesis and release in response to osmotic and non-osmotic stimulation, and that the region of 5′ flanking sequence between −1500 and −532 contains the elements responsible for the effects.

In our previous studies (Refs. 1 and 2), it was shown that protein tyrosine kinase (PTK) inhibitors, radicicol and herbimycin A, inhibit the expression of the mitogen-inducible cyclooxygenase (COX-2) and proinflammatory cytokines. Radicicol and herbimycin A possess polarized double bonds which can conjugate sulphydryl groups of proteins. Parthenolide, the predominant sesquiterpene lactone in European feverfew (Tanacetum parthenium), contains α-methylene-gamma-lactone (MGL) and an epoxide in its structure. These moieties can interact with biological nucleophiles such as a sulfhydryl group. Parthenolide inhibited the expression of COX-2 and proinflammatory cytokines (TNFα and IL-1) in lipopolysaccharide (LPS)-stimulated macrophages. The structure-function relationship indicates that the MGL moiety confers the inhibitory effect. Parthenolide suppressed LPS-stimulated protein tyrosine phosphorylation in the murine macrophage cell line (RAW 264.7). This suppression was correlated with its inhibitory effect on the expression of COX-2 and the cytokines. Among tyrosine phosphorylated proteins, mitogen-activated protein kinases (MAPKs) exhibited the most dramatic inhibition.

Nephrotic syndrome is characterized by water and sodium retention, which leads to edema formation. The nonosmotic stimulation of arginine vasopressin (AVP) release from the pituitary gland has been implicated to be one of the important factors of abnormal water retention in patients with nephrotic syndrome. It is not known, however, whether nephrotic syndrome is associated with stimulation of hypothalamic vasopressin gene expression. Puromycin aminonucleoside is known to cause altered glomerular permeability, which results in experimental nephrotic syndrome in rats. In the present study, therefore, AVP gene expression has been studied in the hypothalamus of rats with puromycin aminonucleoside-induced nephrotic syndrome (PNS). Nephrotic syndrome was induced by a single intravenous injection of puromycin aminonucleoside (50 mg/kg body weight). Nephrotic syndrome was confirmed by urinary protein excretion (control 20.8 +/- 3.5 mg/24 hr v PNS 273.9 +/- 41.4 mg/24 hr; P < 0.0001, n = 6) and serum albumin concentrations (control 4.52 +/- 0.07 g/dL v PNS 2.96 +/- 0.22 g/dL; P < 0.001, n = 6). In PNS rats, plasma AVP was significantly higher than in control rats (control 0.77 +/- 0.10 pg/mL v PNS 2.13 +/- 0.42 pg/mL; P < 0.005, n = 12), even though there were no differences in plasma osmolality (control 292.0 +/- 2.0 mOsm/kg H2O v PNS 290.3 +/- 2.5 mOsm/kg H2O; P = NS, n = 12) or serum sodium concentration (control 142.7 +/- 0.7 v PNS 142.1 +/- 1.1; PNS, n = 12).(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine vasopressin (AVP) binds to two distinct receptors to initiate vasopressor (V1 receptor) and hydroosmotic actions (V2 receptor). Internalization and recycling of the V1 receptor in cultured vascular smooth muscle cells and hepatocytes have recently been demonstrated. However, the receptor cycle of the AVP V2 receptor in the renal collecting tubules has not yet been well defined. Therefore, the present study was undertaken to investigate the AVP V2 receptor cycle, including AVP binding to the surface receptor, internalization and potential recycling in isolated outer medullary collecting tubules. The maximal AVP surface binding was reached in 10 min, and 25 micrograms/ml trypsin completely inhibited the surface binding. A Scatchard plot of 125I-AVP surface binding indicated a single population of V2 receptors with a Kd of 1.92 x 10(-9) M and a Bmax of 1.77 x 10(-11) M or 590 fmoles/mg protein. 81.7% (72-85%) of specific bound receptor was internalized (specific surface binding: 742.8 +/- 111.1 vs internalized binding: 607.3 +/- 27.8 fmoles bound/mg protein). More than 90% of surface bound receptor was recycled to the cell surface after internalization (control surface binding: 584.0 +/- 64.0 vs recycled surface binding: 546.6 +/- 32.0 fmoles bound/mg protein). Cycloheximide (40 micrograms/ml) did not inhibit the receptor recycling (control recycled surface binding: 546.6 +/- 32.0 vs cycloheximide recycled surface binding: 505.0 +/- 54.8 fmoles bound/mg protein), thus suggesting that the receptors were not resynthesized after dissociation from the receptor-ligand complex. These studies therefore demonstrate that the AVP V2 receptor is internalized and recycled in the rat renal collecting tubule.

Impaired ability to excrete a water load occurs in a substantial number of patients with advanced cirrhosis and in animals with experimental cirrhosis. The nonosmotic stimulation of arginine vasopressin release from the pituitary has been implicated as an important factor in the abnormal water excretion in patients and animals with cirrhosis. In this study, arginine vasopressin hypothalamic gene expression was studied in cirrhotic rats. Cirrhosis was induced by a combination of phenobarbital treatment in drinking water and weekly intragastric administration of carbon tetrachloride for 13 to 15 wk. Severe cirrhosis was confirmed by morphological analysis and the presence of ascites. Plasma arginine vasopressin was also significantly higher in rats with cirrhosis (control = 1.77 +/- 0.16 and cirrhotic rats = 4.14 +/- 0.62 pg/ml, n = 9, p < 0.002). Hypothalamic arginine vasopressin messenger RNA was also significantly higher in cirrhotic rats (control = 762.1 +/- 132.3 and cirrhotic rats = 1,834.2 +/- 271.9 pg/hypothalamus, n = 9, p < 0.005). Pituitary arginine vasopressin content was significantly lowered in cirrhotic rats (control = 3.69 +/- 0.98 and cirrhotic rats = 1.57 +/- 0.09 micrograms/pituitary, n = 9, p < 0.05). No difference was seen in hypothalamic arginine vasopressin content between the two groups (control = 4.64 +/- 0.34 and cirrhotic rats = 4.23 +/- 0.33 ng/hypothalamus, n = 9, NS). Oxytocin messenger RNA in the hypothalamus was also not significantly different between the two groups (control = 8.61 +/- 0.68 and cirrhotic rats = 9.33 +/- 0.65 unit of density, n = 9, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

The present study was undertaken to examine vasopressin gene expression in response to a normal versus hypertonic sodium chloride (506 mOsm/kg H2O) intake for 7 days in Sprague-Dawley rats. The animals in both groups demonstrated precision in maintaining constancy of body fluid composition in spite of large differences in sodium and water intakes. Compared with the rats on a normal diet, chronic ingestion of hypertonic sodium chloride resulted in significant increases in total fluid intake (210 +/- 8 mL v 471 +/- 48 mL, P < 0.001) and total urine output (86 +/- 5 mL v 347 +/- 48 mL, P < 0.001), while glomerular filtration rate, hematocrit, serum urea nitrogen, creatinine, serum sodium, and plasma osmolality were unchanged. Without detectable changes in plasma osmolality or intravascular volume, vasopressin release from the pituitary, as measured by plasma and pituitary vasopressin concentrations (1.5 +/- 0.1 pg/mL v 5.9 +/- 1.5 pg/mL, P < 0.01 and 2.0 +/- 0.5 micrograms/pituitary v 0.86 +/- 0.1 micrograms/pituitary, P < 0.01, respectively), was increased in the animals ingesting hypertonic sodium chloride. In addition, vasopressin gene expression as measured by hypothalamic vasopressin mRNA concentrations was significantly increased 1.85-fold (P < 0.001) in the animals ingesting hypertonic sodium chloride. In summary, Sprague-Dawley rats ingesting hypertonic sodium chloride (506 mOsm/kg H2O) were able to maintain sodium and water homeostasis over a 7-day period. Yet, in these animals plasma vasopressin increased, pituitary vasopressin stores decreased, and hypothalamic vasopressin gene expression was stimulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Annals of the New York Academy of SciencesVolume 689, Issue 1 p. 659-662 Vasopressin Gene Expression in Glucocorticoid Hormone-Deficient Rats HEUI-JUNG PYO, HEUI-JUNG PYO Department of Medicine Division of Renal Diseases and Hypertension University of Colorado School of Medicine Denver, Colorado 80262Search for more papers by this authorSANDRA N. SUMMER, SANDRA N. SUMMER Department of Medicine Division of Renal Diseases and Hypertension University of Colorado School of Medicine Denver, Colorado 80262Search for more papers by this authorJIN K. KIM, JIN K. KIM Department of Medicine Division of Renal Diseases and Hypertension University of Colorado School of Medicine Denver, Colorado 80262Search for more papers by this authorROBERT W. SCHRIER, ROBERT W. SCHRIER Department of Medicine Division of Renal Diseases and Hypertension University of Colorado School of Medicine Denver, Colorado 80262Search for more papers by this author HEUI-JUNG PYO, HEUI-JUNG PYO Department of Medicine Division of Renal Diseases and Hypertension University of Colorado School of Medicine Denver, Colorado 80262Search for more papers by this authorSANDRA N. SUMMER, SANDRA N. SUMMER Department of Medicine Division of Renal Diseases and Hypertension University of Colorado School of Medicine Denver, Colorado 80262Search for more papers by this authorJIN K. KIM, JIN K. KIM Department of Medicine Division of Renal Diseases and Hypertension University of Colorado School of Medicine Denver, Colorado 80262Search for more papers by this authorROBERT W. SCHRIER, ROBERT W. SCHRIER Department of Medicine Division of Renal Diseases and Hypertension University of Colorado School of Medicine Denver, Colorado 80262Search for more papers by this author First published: July 1993 https://doi.org/10.1111/j.1749-6632.1993.tb55621.xCitations: 9AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume689, Issue1The Neurohypophysis: A Window on Brain FunctionJuly 1993Pages 659-662 RelatedInformation

Hypothyroidism is associated with abnormalities in renal water handling, which include a delay in excretion of an acute water load, decreased urinary concentrating ability, and increased urine volume. In the present study, we investigated the role of vasopressin in aminotriazole-induced hypothyroidism by measuring vasopressin concentration in the plasma and pituitary along with vasopressin mRNA levels in the hypothalamus. After 5 weeks of aminotriazole treatment, L-thyroxine levels were significantly lower in the experimental animals (122 +/- 8 v 26 +/- 1 nmol/L [9.5 +/- 0.6 v 2.0 +/- 0.1 micrograms/dL]; P less than 0.001). Serum sodium (148 +/- 0.5 v 144 +/- 1.2 mmol/L [mEq/L]; P less than 0.01), and plasma osmolality (311 +/- 2.5 v 304 +/- 1.8 mmol/kg [mOsm/kg] H2O; P less than 0.05) were also lower in the experimental animals. There were no differences in plasma (1.9 +/- 0.4 v 1.5 +/- 0.2 pg/mL) or pituitary (1.5 +/- 0.4 v 1.5 +/- 0.2 microgram/pituitary) vasopressin levels. In addition, steady-state vasopressin mRNA levels were not different between the two groups (1,286 +/- 210 v 1,093 +/- 138 pg/hypothalamus). One week of L-thyroxine replacement resulted in significant increases in serum thyroxine levels without changes in the other variables measured. These results indicate that short-term hypothyroidism, which has been shown to exert substantial effects on renal function, causes only a modest central alteration in the plasma vasopressin-osmolality relationship, which occurs in the absence of detectable changes in vasopressin synthesis.

Arginine vasopressin (AVP) is known to be increased in patients and experimental animals with chronic cardiac failure (CCF). The importance of an increase in biosynthesis of AVP in the hypothalamus has, however, not heretofore been investigated and is the purpose of the present study. CCF secondary to infarction of myocardial tissue was induced by ligation of the left anterior descending coronary artery and sham operated animals served as controls. Four weeks later hypothalamic AVP mRNA was determined by solution hybridization using sense and anti-sense strand RNA. The blood pressure was lower in CCF than sham animals (131.2 +/- 3.1 vs. 112.8 +/- 4.0 mm Hg, P less than 0.05) and the total heart, and right and left ventricle weights were significantly higher in CCF rats. Plasma AVP was higher in CCF (sham 6.78 +/- 0.30; CCF 11.46 +/- 0.64 pg/ml, P less than 0.001) and plasma atrial natriuretic peptide was also higher in CCF than sham animals (205 +/- 36 vs. 554 +/- 56 pg/ml, P less than 0.001). The AVP mRNA in hypothalamus was significantly higher in CCF than sham animals (55.5 +/- 3.7 vs. 95.9 +/- 4.0 pg/micrograms total RNA, P less than 0.001). There was no difference in beta-actin mRNA in the hypothalamus of sham and CCF rats, indicating that the AVP-mRNA increase was specific in CCF. These results therefore demonstrate that increased AVP biosynthesis in the hypothalamus, in addition to release of the hormone from the posterior pituitary, may occur in CCF.

Atrial natriuretic factor (ANF) has been suggested to exert a tubular effect on the mammalian nephron, perhaps in part by interacting with other hormones. In the present study, the effect of ANF was examined on glomeruli (Gm) and different renal tubule segments including medullary (MAL) and cortical thick ascending limb (CAL) and cortical (CCT), outer medullary (OMCT) and inner medullary collecting tubules (IMCT). This effect of ANF was assessed by alteration in adenylate cyclase and cGMP in the various nephron segments in the presence and absence of arginine vasopressin (AVP), parathyroid hormone (PTH) and calcitonin (SCT). An effect of ANF (10(-8) M) was not demonstrated on adenylate cyclase (fmol cAMP formed/30 min/micrograms protein) in Gm, CAL, MAL, CCT, OMCT or IMCT. Nor did ANF (10(-8) M) interfere with the effect of PTH (5 IU/ml) on the Gm (PTH 35.1 +/- 3.7 vs. PTH + ANF 32.5 +/- 1.8, NS), CAL (PTH 50.5 +/- 10.9 vs. PTH + ANF 46.2 +/- 1.4, NS) or AVP (10(-8) M) on the CCT (AVP 40.8 +/- 6.6 vs. AVP + ANF 33.0 +/- 3.1, NS), OMCT (AVP 56.0 +/- 11.8 vs. AVP + ANF 42.1 +/- 6.7, NS), IMCT (AVP 66.5 +/- 4.6 vs. AVP + ANF 53.5 +/- 7.0, NS) or MAL (AVP 15.5 +/- 1.6 vs. AVP + ANF 14.0 +/- 2.6, NS). ANF also did not affect SCT (1.5 x 10(-8) M)-induced adenylate cyclase on CCT (SCT 69.8 +/- 11.3 vs. SCT + ANF 79.9 +/- 7.2, NS). ANF (10(-8) M), however, significantly increased cGMP in the Gm (6.4 +/- 1.7 to 121.3 +/- 32.4 fmol/micrograms protein, P less than 0.001) and IMCT (0.63 +/- 0.16 to 1.46 +/- 0.29 fmol/micrograms protein, P less than 0.05). However, no effect of ANF on cGMP was observed in the CAL, CCT, OMCT, and MAL even at 10(-7) M ANF. PTH (5 IU/ml) did not alter either basal or ANF-stimulated cGMP in the Gm. Also, specific ANF binding was studied in the microdissected IMCT. Kd was 6.08 x 10(-9) M and Bmax was 8.07 x 10(-11) M.(ABSTRACT TRUNCATED AT 250 WORDS)

This in vitro study was undertaken to determine the changes in Ca2+ kinetics and cell shape of cultured putative glomerular mesangial cells in the rat in response to angiotensin II (ANG II). Intracellular Ca2+ ([Ca2+]i) was measured using quin 2. ANG II-stimulated Ca2+ efflux was also determined. ANG II induced rapid concentration-dependent increases in [Ca2+]i and Ca2+ efflux. ANG II also induced contraction of mesangial cells as assessed by alterations in cell shape. Even in Ca2+-free medium, ANG II increased [Ca2+]i and Ca2+ efflux, but to a lesser extent. Under this condition, contraction of mesangial cells induced by ANG II was also observed. Readdition of extracellular Ca2+ after the ANG II-induced increase in [Ca2+]i caused a second and slower [Ca2+]i increase. High potassium (50 mM) induced a change of [Ca2+]i, but to a lesser extent compared with the ANG II-induced change. The Ca2+ channel blocker verapamil (5 x 10(-5) M) partially inhibited ANG II-induced Ca2+ influx but totally blocked the increase in [Ca2+]i induced by high potassium. Verapamil did not inhibit ANG II-stimulated Ca2+ efflux or the change in cell shape. Dantrolene (10(-4) M), a blocker of Ca2+ release from endoplasmic reticulum, inhibited ANG II-stimulated Ca2+ efflux and change in cell shape. These results indicate that ANG II rapidly increases [Ca2+]i in cultured rat mesangial cells, in part by mobilizing Ca2+ from dantrolene-sensitive intracellular pools and in part through activation of receptor-operated and voltage-dependent Ca2+ channels. The [Ca2+]i mobilization, however, seems to be the primary modulator of initial glomerular mesangial cell contraction.