CAPILLARY NETWORK AND FIBER SIZE IN RAT SKELETAL MUSCLE CHANGES DIFFERENTIALLY TO AGING AND TRAINING

Abstract

1637 In order to examine 1) the aging-related changes of the capillary network and the muscle fiber size, and 2) the effect of running training on it, morphometrical analyses were performed on the cross-sections of the perfusion-fixed rat plantaris muscles. Untrained animals were sacrificed at 4 months old (group C4; B.W. 466 ± 9 g), 19 months old (group C19; B.W. 595±30 g) and trained at 19 months old (group T19; B.W. 584±16 g). The trained rats had run on a treadmill at 20 m/min, 60 min/day, 5 days/wk from 17 months of age for 9 wks. The aging-related decrease in mean fiber cross-sectional area was observed (C4; 2221 ± 56 μm2 vs. C19; 2022 ± 144 μm2), but the training caused remarkable hypertrophy of the fiber against atrophy with aging (T19; 2664 ± 129 μm2). Capillary density (CD: no/mm2) and capillary-to-fiber ratio (CF ratio) increased with aging (CD − C4; 1111 ± 48 vs. C19; 1377 ± 97, CF ratio − C4; 2.00±0.07 vs. C19; 2.56±0.12), which was not influenced by training (CD − T19; 1065±35, CF ratio − T19; 2.38±0.10). Neither aging nor training altered capillary luminal diameter (LD − C4; 5.24±0.12 μm, C19; 5.39±0.07 μm, T19; 5.25±0.12 μm). In conclusion, 1) capillary network and muscle fiber area were differentially influenced with aging and running training and 2) LD was rather stable against aging and training, comparing with other capillary parameters.