Effects of Exercise Training on Skeletal Muscle Vascular Geometry in Young and Old Rats

Abstract

With aging, there is a reduction in the number of feed arteries perforating the gastrocnemius muscle likely resulting from a reduction in spontaneous physical activity in old rats. We tested the hypothesis that exercise training would ameliorate age-related differences in vascular geometry in skeletal muscle. METHODS: Young and old male Fischer 344 rats were divided into young sedentary (YS), old sedentary (OS), young exercise-trained (YT) or old exercise-trained (OT) groups, where training consisted of 10-12 weeks of treadmill exercise. At the end of the training period, all feed arteries perforating the gastrocnemius muscle were isolated, cannulated and maximally dilated for measurement of luminal diameters. RESULTS: In young rats with exercise training there was a significant increase in the number of feed arteries perforating the gastrocnemius muscle (YS, 8.9±0.1 vs. YT, 10.3±0.2 arteries, p<0.05), whereas exercise training did not affect the number of feed arteries in the aged animals (OS, 7.6±0.2; OT, 7.8±0.2 arteries). However, in old animals there was an increased average luminal cross-sectional area (CSA) in feed arteries with exercise training. DISCUSSION: Contrary to our hypothesis, with exercise training there was no apparent increase in the number of feed-arteries perforating the gastrocnemius muscle in old animals. The increased CSA of the feed arteries in old exercise trained animals suggests a structural enlargement of luminal diameters in this group may be a compensatory mechanism to augment blood flow to the muscle. However, the greater number of feed-arteries in young-trained muscle may allow a more precise matching of blood-flow to muscle O2 uptake. Supported by NASA grant NCC2-1166 and NIH F32 AG25622.