Vascular vasopressin receptors mediate phosphatidylinositol turnover and calcium efflux in an established smooth muscle cell line

Abstract

Vasopressin-induced phosphatidylinositol turnover and mobilization of intracellular Ca 2+ was studied using an established smooth muscle cell line (A-10). The cells were subcloned to ensure a monoclonal cell population. The accumulation of inositol mono-, di-, and tris-phosphates (IP 1, IP 2, and IP 3, respectively), and the mobilization of intracellular Ca 2+ were dependent on the time of incubation and the concentration of arginine vasopressin (AVP). IP 1, IP 2, and IP 3 were significantly elevated after 15 sec and remained elevated for up to 2 hr. The concentrations of AVP required for half-maximal stimulation of IP 1, IP 2, and IP 3 formation were 2, 12, and 4 nM, respectively. LiCl was required to observe the accumulation of inositol phosphates in response to AVP. Significant 45Ca 2+ efflux was observed within 15 sec after exposure to AVP. By employing the vasopressin receptor subtype selective antagonists [d(CH 2) 5Tyr(Me)AVP, V 1; d(CH 2) 5D-Tyr(Et)VAVP, V 1/V 2; d(CH 2) 5D-I1eVAVP, V 2] and agonists [AVP, V 1/V 2; dDAVP, V 2; dVDAVP, V 2], we found that the vasopressin-induced stimulation of phosphatidylinositol turnover and 45Ca 2+ efflux were mediated by receptors of the vascular V 1 subtype. Pertussis toxin pretreatment partially inhibited vasopressin-induced phosphatidylinositol turnover. These data demonstrate that activation of V 1 receptors of vascular smooth muscle cells resulted in enhanced phosphatidylinositol turnover and mobilization of intracellular Ca 2+.