THE INOSITOL PHOSPHATE RESPONSE TO THROMBIN IN RAT RIGHT ATRIA DIFFERS FROM THE RESPONSE TO NORADRENALINE

Addition of thrombin to isolated [H-3]inositol-labelled rat right atri a stimulated the release of H-3-labelled inositol phosphates. The thro mbin response was smaller than the response to noradrenaline and gener ated a different spectrum of inositol phosphates. Unlike the inositol phosphate response to noradrenaline, the thrombin response was inhibit ed by pertussis toxin treatment and by the phospholipase C inhibitor U -73122 (1-(6-((17 0)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione). T he data indicate that the thrombin stimulation involves different G-pr oteins and phospholipase C isoforms from those which couple alpha(1)-a drenoceptors in the myocardium.