Renal and endocrine responses to a renin inhibitor, enalkiren, in normal humans.
Interpretation of renin-angiotensin blockade with angiotensin converting enzyme inhibitors is potentially confounded by their multiple effects. We used a selective renin inhibitor (enalkiren, A-64662) to explore the renal and endocrine effects of angiotensin II in healthy men. Each received 90-minute enalkiren infusions at 2-day intervals, on a low (10 mmol, 16 subjects) and high (200 mmol, 12 subjects) salt diet. Plasma renin activity, immunoreactive plasma angiotensin II and aldosterone concentrations, inulin, and p-aminohippurate clearance were measured by standard methods. Plasma renin activity fell at 0.1 micrograms/kg, but the threshold for biologic effect was 256 micrograms/kg, where plasma immunoreactive angiotensin II and aldosterone concentration fell, and renal plasma flow rose (p less than 0.01). The maximal renal vascular response (+152 +/- 23 ml/min/1.73 m2) occurred at 512 micrograms/kg (p less than 0.01). Diastolic and mean blood pressure fell modestly but significantly (p less than 0.05). Responses were limited on a high salt diet. We confirm that conventional plasma renin activity measurement is misleading in humans receiving a renin inhibitor. The renal vascular response to renin inhibition in this study appeared to substantially exceed reported responses to angiotensin converting enzyme inhibition, perhaps reflecting a crucial and relatively inaccessible intrarenal locus.
Cordero
P
P
Department of Medicine, Harvard Medical School, Boston, Mass.
Fisher
N D
ND
Moore
T J
TJ
Gleason
R
R
Williams
G H
GH
Hollenberg
N K
NK
D000328:Adult; D000450:Aldosterone / Q000097:blood; D000804:Angiotensin II / Q000096:biosynthesis / Q000097:blood; D001794:Blood Pressure; D004039:Diet, Sodium-Restricted; D004151:Dipeptides / Q000494:pharmacology*; D004702:Endocrine Glands / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007444:Inulin / Q000097:blood; D007668:Kidney / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012083:Renin / Q000097:blood
D004151:Dipeptides; C056622:enalkiren; D000804:Angiotensin II; D000450:Aldosterone; D007444:Inulin; D012083:Renin