Effects of captopril, an angiotensin-converting enzyme inhibitor, in normotensive sodium-replete volunteers.
Captopril (SQ 14 225) was administered to normotensive, sodium-replete volunteers in order to investigate the relationships between its haemodynamic effects and effects on sympathetic activity, the renin-angiotensin-aldosterone system, and plasma-converting enzyme activity. Following the administration of captopril (25 mg) orally, mean arterial pressure fell (supine 89.1 +/- 5.9 to 81.1 +/- 3.3 mm Hg, p less than 0.01; erect 98.5 +/- 5.5 to 87.4 +/- 6.7 mm Hg, p less than 0.01) but heart rate did not change. Plasma noradrenaline rose; plasma renin activity and angiotensin I concentration rose, while angiotensin II and aldosterone fell; plasma-converting enzyme was inhibited for 6 h. The extent of blood pressure reduction and converting enzyme inhibition was closely correlated (r = 0.92, p less than 0.001). Plasma captopril concentration was directly related to converting enzyme inhibition in an in vitro study using plasma from the same subjects. In the absence of a convenient assay of captopril, converting enzyme may be used as an index of captopril concentration in the further study of kinetic and dynamic relationships.
D000328:Adult; D000450:Aldosterone / Q000097:blood; D000804:Angiotensin II / Q000097:blood; D000806:Angiotensin-Converting Enzyme Inhibitors; D001794:Blood Pressure / Q000187:drug effects; D002216:Captopril / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000097:blood; D007703:Peptidyl-Dipeptidase A / Q000097:blood; D011392:Proline / Q000031:analogs & derivatives*; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System / Q000187:drug effects*; D012964:Sodium / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000187:drug effects*
D000806:Angiotensin-Converting Enzyme Inhibitors; D000804:Angiotensin II; D000450:Aldosterone; D011392:Proline; D002216:Captopril; D012964:Sodium; D007703:Peptidyl-Dipeptidase A; D012083:Renin; D009638:Norepinephrine