The inositol phosphate response to thrombin in rat right atria differs from the response to noradrenaline

Addition of thrombin to isolated [3H]inositol-labelled rat right atria stimulated the release of 3H-labelled inositol phosphates. The thrombin response was smaller than the response to noradrenaline and generated a different spectrum of inositol phosphates. Unlike the inositol phosphate response to noradrenaline, the thrombin response was inhibited by pertussis toxin treatment and by the phospholipase C inhibitor U-73122 (1-(6-((17 beta-3- methoxyestra-1,3,5(10)-trien-17-yl)amino)amino)hexyl)-1H- pyrrole-2, 5-dione). The data indicate that the thrombin stimulation involves different G-proteins and phospholipase C isoforms from those which couple alpha 1-adrenoceptors in the myocardium.