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1 Department of Exercise and Sport Science, East Carolina Univ, Greenville, NC, USA; Department of Human Performance Laboratory, East Carolina Univ, Greenville, NC, USA
2 Department of Exercise and Sport Science, East Carolina Univ, Greenville, NC, USA; Department of Physiology, East Carolina Univ, Greenville, NC, USA; Department of Human Performance Laboratory, East Carolina Univ, Greenville, NC, USA
3 Department of Surgery, East Carolina Univ, Greenville, NC, USA
* To whom correspondence should be addressed. E-mail: gavint{at}mail.ecu.edu.
In humans, the majority of studies demonstrate an age associated reduction in the number of capillaries surrounding skeletal muscle fibers, however recent reports in rats suggest that muscle capillarization is well maintained with advanced age. In sedentary and trained men, aging lowers the number of capillaries surrounding type II, but not type I skeletal muscle fibers. The fiber type specific effect of aging on muscle capillarization is unknown in women. Vascular endothelial growth factor (VEGF) is important in the basal maintenance of skeletal muscle capillarization and lower VEGF expression is associated with increased age in non-skeletal muscle tissue of women. Compared to young women (YW), we hypothesized that aged women (AW) would demonstrate: 1) lower muscle capillarization in a fiber type specific manner; and 2) lower VEGF and VEGF receptor expression at rest and in response to acute exercise. Nine aged (70 + 8) and eleven young (22 + 3) sedentary women had vastus lateralis muscle biopsies obtained prior to and at 4 hr after a sub-maximal exercise bout for the measurement of morphometry and VEGF and VEGF receptor expression. In AW compared to YW, muscle capillary contacts was lower overall (YW: 2.36 + 0.32; AW: 2.08 + 0.17 capillaries); specifically in type II (YW: 2.37 + 0.39; AW: 1.91 + 0.36 capillaries), but not type I fibers (YW: 2.36 + 0.34; AW: 2.26 + 0.24 capillaries). Muscle VEGF protein was 35% lower at rest and the exercise-induced increase in VEGF mRNA was 50% lower in AW compared to YW. There was no effect of age on VEGF receptor expression. These results provide evidence that in the vastus lateralis of women: 1) capillarization surrounding type II muscle fibers is lower in aged compared to young; and 2) resting VEGF protein and the VEGF mRNA response to exercise are lower in aged compared to young.
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