Aging is associated with endothelial dysfunction in the human forearm vasculature

OBJECTIVE: Our objective was to examine the role of the endothelium in main taining vascular tone in the basal as well as in the contracted state durin g aging. DESIGN/PARTICIPANTS : Responses to brachial artery infusion of acetylcholin e in presence and absence of N-G-nitro-L-arginine methyl ester (L-NAME) and to angiotensin II were studied in 11 young and 12 old white subjects. MEASUREMENTS: Strain gauge plethysmography was used to measure forearm vasc ular resistance (FVR). The dose of acetylcholine at 50% maximal observed de crease in forearm vascular resistance (EC50) was significantly higher (11.0 +/- 1.59 vs 7.07 +/- .65 mu g/min, respectively; mean +/- SEM; P < .05) an d the FVR at maximal acetylcholine effect (Emax) remained greater (12.6 +/- 1.75 vs 7.15 +/- 1.25 mm Hg/100 mt tissue volume/min; P < .02) in old comp ared with young subjects. Acetylcholine effect was significantly reversed b y concomitant administration of L-NAME, as indicated by the increase in EC5 0 (old, 20.2 +/- 3.69; young, 11.9 +/- 1.68 mu g/min) RESULTS: There was no age-related difference in sodium nitroprusside-induce d decrease in FVR. The EC50 and Emax for angiotensin II-mediated increase i n FVR were 7.87 +/- 1.15 and 8.36 +/- 1.00 ng/min (EC50) and 5.30 +/- .67 v s 6.56 +/- 1.25 mm Hg/100 mt tissue volume/min (Emax), and these were not d ifferent in old and young subjects, respectively. CONCLUSIONS: These data indicate that aging is associated with impaired end othelial- dependent vascular relaxation and that this is selective, with no age-related change in endothelial-independent vascular relaxation or angio tensin II-mediated vascular contraction.