Age and Nitric Oxide in Active Cutaneous Vasodilation During Whole Body Heating

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.