Age and the renal blood supply: renal vascular responses to angiotensin converting enzyme inhibition in healthy humans.
OBJECTIVE
To assess the relation between age, sodium intake, renal blood flow (RBF) and the renal vascular response to an angiotensin converting enzyme (ACE) inhibitor, captopril.


METHODS
Blood flow studies were performed before and during the acute response to an oral 25-mg dose of captopril, selected to induce a maximal response, after 5 to 7 days on a metabolic ward, sufficient time to have achieved external balance on a fixed low-salt (10 mE/day) or high salt (200 mEq/day) diet. Blood flow was measured as radioxenon transit through the kidney.


METHODS
The study was performed on a metabolic ward, the Clinical Research Center, and in the Cardiovascular Radiology Laboratories of the Brigham and Women's Hospital in Boston.


METHODS
The participants, all community dwellers, were potential kidney donors, in a renal transplant program. They were thought to be sufficiently healthy to consider donation of a kidney. The age range was 18 to 69 years.


RESULTS
Renal blood flow showed the anticipated decline with increasing age, whether the subjects were on a restricted or a liberal salt intake. Captopril induced an acute increase in RBF, averaging 88 +/- 7 mL/100 g/min in subjects on a high-salt diet, but no influence of age was identified on the renal vasodilator response on either diet. Increasing age did not limit the renal vasodilator response, although subjects beyond the sixth decade were not studied.


CONCLUSIONS
The limited renal vascular response to vasodilators we had documented in earlier studies does not extend to ACE inhibitors. Although ACE inhibitors lack the pharmacological specificity required to prove a role for angiotensin II (Ang II), the data are compatible with a contribution of Ang II to the maintenance of renal vascular tone that does not change with increasing age, at least to 70 years of age.
Hollenberg
N K
NK
Department of Medicine, Harvard Medical School, Boston, MA 02115.
Moore
T J
TJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood / Q000502:physiology*; D002216:Captopril / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012079:Renal Circulation / Q000187:drug effects*; D012083:Renin / Q000097:blood
D002216:Captopril; D012083:Renin