Abstract
Cutaneous active vasodilation during whole body heating is diminished in the elderly. In young healthy subjects, nitric oxide (NO) dependent vasodilation accounts for approximately 30% of cutaneous active vasodilation. Purpose: The goal of this study was to determine whether the reduced active vasodilation in the skin of older subjects is due to diminished NO-dependent vasodilation. Methods: Six young (23 ± 2 years, 4 men, 2 women) and four older (77 ± 4 years, 3 men, 1 woman) subjects were instrumented with two intradermal microdialysis fibers in the skin of the non-dominant forearm. One site served as a control (Ringer's infusion only) and the second site was perfused with 10mM L-NAME to inhibit NO production throughout the protocol. Skin blood flow was measured at each site using laser-Doppler flowmetry (LDF; Moor LDF4) and blood pressure was measured using a Portapres device (Ohmeda). Cutaneous vascular conductance (CVC) was calculated as LDF/Mean Arterial Pressure, and values are expressed as a percentage of maximal vasodilation (28mM nitroprusside). Results: In the control site CVC was 63.6 ± 13.5% (mean ± SEM) in the young and 39.8 ± 12.8% in the older subjects. NO-synthase inhibition reduced CVC by 24.3 ± 5.9% in the young subjects versus 15.2 ± 9.3% in the older subjects. Conclusion: Our preliminary results suggest that diminished NO-dependent vasodilation in the elderly contributes to the age-related reduction in cutaneous active vasodilation during whole body heating.
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