INCREASED PLATELET REACTIVITY TO PROSTAGLANDIN-E(1) IN HYPERTENSION IS LINKED WITH ALTERED SIGNAL-TRANSDUCTION

Prostaglandin E1 has been shown to induce a greater accumulation of cA MP in platelets from spontaneously hypertensive (SHR) than in platelet s from normotensive (Wistar-Kyoto, WKY) rats (Circ. Res. 1978;43:583-5 91. Thromb. Res. 1988;49:5-21). This study was conducted to determine the mechanisms of increased platelet reactivity to PGE1 in hypertensio n. The number of PGE1 binding sites/platelet (WKY 280 +/- 8, SHR 287 /- 5) as well as the K(d) for WKY (105 +/- 11 nmol/L) and SHR (120 +/- 14 nmol/L) were found to be similar in WKY and SHR rats. PGE1-induced GTPase activity was determined using WKY and SHR platelet membranes. T he basal GTPase activity was similar in WKY and SHR platelets. Incubat ion of membranes with PGE1 (3 mumol/L) for 1 min increased GTPase acti vity by 46% in WKY and by 806% in SHR. Incubation of platelets with 1. 0 mmol/L IBMX (3-isobutyl-1-methyl-xanthine) for 4 min resulted in a 3 27 +/- 57% and 320 +/- 11% increase in cAMP in WKY and SHR platelets, respectively. In other experiments, incubation of platelets with 3, 10 and 100 mumol/L forskolin, induced similar increases in cAMP levels i n WKY (103 +/- 12%, 530 +/- 42%, 784 +/- 41%) and SHR (111 +/- 13%, 46 1 +/- 18%, 756 +/- 28%) platelets. These data lead us to suggest that the greater accumulation of cAMP induced by PGE, in SHR than in WKY pl atelets is linked with altered PGE1-receptor mediated signal transduct ion at the G-protein level.