When subjected to total body heating and exercise, skin blood flow does not increase as much in elderly as in young subjects. It is not known whether this age-related decline is due to the autonomic dysfunction that develops in the elderly or to changes at the level of the blood vessels of the skin. We used local heating of the forearm to quantify the intrinsic ability of the cutaneous vasculature to dilate in seven young men (avg age 31 yr) and seven elderly men (avg age 71 yr). A water spray was used to maintain a neutral skin temperature of 32–35 degrees C for > 10 min, followed by 60 min of a 42 degrees C skin temperature to induce maximal skin blood flow. Forearm blood flow was measured by venous occlusion plethysmography with a mercury-in-Silastic circumference gauge. At the neutral skin temperature, forearm blood flows in the elderly subjects were comparable to those in the young subjects: 3.0 +/- 0.5 vs. 2.8 +/- 1.0 ml.min-1 x 100 ml-1. During the last 10 min of heating, however, blood flows were much lower in the elderly than in the young subjects: 11.1 +/- 2.7 vs. 19.9 +/- 5.2 ml.min-1 x 100 ml-1 (P = 0.002). We conclude that aging results in a reduction of the maximal conductance of the cutaneous vasculature.
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