Prostaglandin excretion after furosemide in normal and low-renin essential hypertension

We examined the urinary excretion of prostaglandin (PG)E2 and PGF2 alpha before and 15 min after stimulation with the acutely vasodilating agent furosemide in 25 normotensive controls and 81 patients with essential hypertension (EH). After furosemide administration, PGE2 excretion was lower in patients with EH (P less than 0.02). Excretion rates of PGF2 alpha and of sodium, and urinary volume in hypertensive patients were not significantly different from the values found in normotensive controls. Patients with low-renin essential hypertension (LREH) had a significantly reduced excretion of both PGE2 and PGF2 alpha before and after administration of furosemide as compared to controls. The difference in PGF2 alpha excretion was also significant when LREH patients were compared to those with normal-renin essential hypertension (NREH). Patients with LREH were older and excreted less potassium than patients with NREH or normotensive controls. We conclude that the reduced PG excretion immediately after furosemide administration in patients with EH reflects a diminished capacity of the hypertensive kidney to generate prostaglandins which exert an overall vasodilating effect. Since renin secretion is under the control of renal PG formation, the decreased responsiveness of plasma renin activity (PRA) observed in patients with EH and predominantly in those with LREH may be the consequence of a decreased renal cortical PG generation. Alternatively, mechanisms that reduce both PRA and PG generation have to be considered.