Altered cellular distribution of hexokinase in skeletal muscle after exercise.

The purpose of this study was to determine the effects of a single period of swim exercise to exhaustion on the cellular distribution of hexokinase in rat skeletal muscle. The gastrocnemius muscle from male rats exercised (n = 16) to exhaustion or allowed to remain inactive (n = 14) was analyzed for hexokinase activity (HK) in the whole muscle homogenate and the mitochondrial-rich fraction. Although exercise produced a slight, non-significant, increase in HK activity in the whole muscle homogenate (p less than 0.09), HK activity in the mitochondrial-rich fraction was significantly increased in the exercised muscle (p less than 0.02). This shift in the cellular distribution of HK is towards the more active mitochondrial bound form and indicates an enhanced regulation of HK activity during physical exercise.