Platelet activation and prostacyclin release in essential hypertension

To evaluate platelet activation thromboxane A2 (TxA2) and beta-thromboglobulin (beta TG) were used as markers and in addition we studied the biosynthesis of prostacyclin. Synthesis of TxA2 and prostacyclin was assessed by measurement of urinary metabolites. Fifteen untreated hypertensive patients (HT) and 15 age-matched normotensive controls (NT) were investigated at rest, during and after exercise. HT patients were re-examined after 3 months on enalapril. During basal conditions there was no difference in the excretion of Tx-M, PGI-M or beta TG between the groups. During strenuous exercise HT exhibit a significantly higher increase in prostacyclin synthesis (162%) compared to NT (76%). The levels of beta TG increased with 82% in the HT and 24% in the NT group, Tx-M increased with 27% and 23% respectively. Treatment with the ACE-inhibitor enalapril did not significantly alter these findings. These results indicate that there is no evidence of basal platelet activation in early essential hypertension. Strenuous exercise leads to some increase in Tx-M in both groups, with no pronounced differences between the groups. Hypertensive patients exhibit a significantly increased prostacyclin response to exercise which could be due to differences in vessel-wall reactivity. Enalapril seems to exert no effect on platelet activation or on prostacyclin biosynthesis.