Plasma renin activity, blood uric acid and plasma volume in pregnancy-induced hypertension

Plasma renin activity (PRA), plasma aldosterone (PA), blood uric acid (BUA), plasma concentrations of catecholamines (Pcat) and plasma volume (PV) were measured simultaneously in 24 patients with pregnancy-induced hypertension (PIH). This hypertensive group was divided into labile (LH) and persistent hypertension (PH) groups according to the response of their blood pressure to home bed rest. Compared to normal theoretical values, PV was decreased in both hypertensive groups (LH = -7%; PH = -14%). Compared to a control group (C) of 16 normotensive pregnant women, PRA was higher in LH and lower in PH whereas PA was lower in both hypertensive groups. BUA was higher than in C in both hypertensive groups. No difference in PCat was found between the three groups. In the PH group negative correlations were found between BUA and PRA, as well as between BUA and PV but no correlation between PRA and PV nor between Pcat and BUA were found.

LH and PH are two pathophysiologically different entities in PIH. In PH renin secretion is not appropriate to hypovolaemia and therefore not primarily involved in the pathogenesis of hypertension. Hypovolaemia may play a role in the increase of BUA in PIH.