Acute and chronic effects of captopril on bicyclo-PGEm, the stable bicyclic end product of prostaglandin E2 in essential hypertension.

Hemodynamic and hormonal actions of acute (50 mg) and chronic (150 mg/day) captopril were tested in 10 patients with essential hypertension. Under short-term conditions blood pressure was reduced, heart rate and plasma adrenaline did not change, plasma angiotensin II and plasma aldosterone decreased. Plasma renin activity, basal plasma noradrenaline and bicyclo-PGEm, a novel stable metabolite of prostaglandin E2, increased after captopril. With chronic captopril treatment blood pressure was reduced after 4 weeks before readministration of captopril, heart rate did not change, plasma renin activity and bicyclo-PGEm remained elevated for 12 h after the last captopril dose. Angiotensin II remained suppressed, aldosterone and plasma catecholamines did not change between doses. Readministration of captopril led to a further reduction in blood pressure. Angiotensin II and aldosterone were further suppressed, bicyclo-PGEm levels increased from a higher baseline. Heart rate and plasma catecholamines did not change. Taken together, the results suggest that prostaglandin E2 is involved in the acute and chronic hypotensive response of captopril in patients with essential hypertension.