To investigate the role of the renin-angiotensin (R-A) system in the release of renal prostaglandin E (PGE), urinary excretion of PGE, plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were measured before and after the manipulation of the R-A system in hypertensive patients. After 7 days of the control sodium diet, the R-A system was stimulated by a combination of low sodium diet and oral administration of furosemide for 7 days. From the 4th day of sodium restriction, 40 mg/day of propranolol was administered per os for 2 days, and the dose was doubled for the following 2 days. PRA and PAC were significantly increased after the sodium restriction, but no change in urinary excretion of PGE was observed. Additional administration of propranolol for the following 4 days suppressed PRA significantly and PAC moderately, but it also failed to change urinary excretion of PGE. These results may suggest that renal medullary PGE synthesis, as reflected in urinary excretion of PGE, is not strongly dependent on the R-A system in these hypertensive patients.
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