Intracellular free calcium transients induced by norepinephrine in rat aortic smooth muscle cells in primary culture

Abstract

In cultured rat arterial smooth muscle cells treated with quin 2, cytosolic Ca 2+ transients induced by norepinephrine were recorded microfluorometrically. In the presence or absence of extracellular Ca 2+, norepinephrine induced transient and dose-dependent elevations in cytosolic Ca 2+, with a similar time course, the peak levels being observed at 2 min. These transient elevations in cytosolic Ca 2+ were dose-dependently inhibited by alpha-adrenergic antagonists, the order of potency being prazosin > phentolamine > yohimbine, irrespective of the presence of extracellular Ca 2+. We propose that with or without extracellular Ca 2+, norepinephrine activates mainly alpha-1 adrenoceptors leading to a release of Ca 2+ from intracellular stores. This would explain the transient elevation in cytosolic Ca 2+ in rat aortic vascular smooth muscle cells in primary culture.