Effect of acute high-intensity exercise in normobaric hypoxia on Thoroughbred skeletal muscle.

Abstract

We examined the effect of transient hypoxic exposure during high-intensity exercise on satellite cell activation and angiogenesis in Thoroughbred skeletal muscle. Six Thoroughbreds horses (6.3±0.8 years old) ran on a treadmill in normoxia (N; FIO2=21%) and hypoxia (H; FIO2=16%) at the same speed for the same duration, and oxygen consumption and plasma lactate and hemoglobin concentrations were measured. In addition, muscle biopsy samples were obtained from gluteus medius muscle before exercise and immediately, 4 hours, 24 hours, 3 days and 7 days after exercise, and immunohistochemical analysis and relative quantitative analysis of mRNA expression using real-time RT-PCR were performed. Oxygen consumption during exercise in H was 29% lower than that in N, and plasma lactate concentration in H was 47% higher than that in N. The mRNA expressions of satellite cell activation-related factors slightly increased, but the mRNA expressions of factors related to angiogenesis and mitochondrial biogenesis slightly decreased. Fluorescence-stained basal lamina evaluation in stacked images 7 days after exercise showed no difference in capillary density between the two groups. These results suggest that transient hypoxic exposure during exercise increases the contribution of the glycolytic energy supply and promotes satellite cell activation, but does not facilitate angiogenesis and mitochondrial biogenesis.