The Role of Urinary PGE₂and Renin-Angiotensin-Aldosterone System in the Pathogenesis of Essential Hypertension

In a group of 26 patients diagnosed as essential hypertensive (EH) and in a control group (CG) of 27 normotensive volunteers the urinary excretion of PGE2, plasma renin activity (PRA) and plasma aldosterone were measured. EH patients were classified into normoreninemic (NREH) (n = 21) and hyporeninemic (LREH) (n = 5) by the response of PRA to the combined stimuli of ambulation and furosemide. Urinary PGE2 excretion was higher in NREH than in CG (p less than 0.05) while LREH showed values lower than in CG (p less than 0.001). Plasma aldosterone levels were similar in the three groups. In CG and EH patients PRA and urinary PGE2 were closely related (CG r = 0.516, p less than 0.05, EH patients r = 0.674, p less than 0.001). Indomethacin administration induced a decrease of PGE2 in both CG (n = 8) and NREH (n = 8) (p less than 0.01). In contrast, indomethacin induced no changes in PGE2 excretion of LREH (n = 5). Furthermore in the group of patients with NREH indomethacin induced a significant increase in blood pressure (p less than 0.01) and body weight (p less than 0.01) while glomerular filtration rate, 24 hour natriuresis PRA and plasma aldosterone decreased (p less than 0.01). On the contrary, in LREH indomethacin did not alter any of the parameters measured. These results indicate that LREH and NREH may be regarded as two different populations distinguishable not only by different secretion of PRA but also by different excretion of PGE2 in urine and by their characteristic response to indomethacin.