Vasopressin-induced calcium increases in smooth muscle cells from spontaneously hypertensive rats

Cytosolic free Ca2+ concentrations ( Ca2+]i) were measured in smooth muscle cells (SMC) from spontaneously hypertensive rats (SHR) and age and sex matched Wistar-Kyoto rats (WKY). Resting levels of Ca2+]i were 114 +/- 6 nM and 116 +/- 5 nM in SMC from WKY and SHR, respectively. Angiotensin II (AII) induced a dose-dependent large increases in Ca2+]i in SMC. There were no significant differences in resting or AII-stimulated levels of Ca2+]i when SMC from WKY and SHR were compared. Arg-vasopressin (AVP) caused a similar but smaller Ca2+]i increase than AII in SMC. AVP caused larger Ca2+]i increases in SMC from SHR than in SMC from WKY. Although concentrations of AVP higher than those ordinarily detected in plasma were necessary to obtain different responses between SHR and WKY, these differences may be related to the pathogenesis of hypertension.