Effect of physical exercise on the permeability of the cellular membrane to enzymes and its mechanism

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The purpose of the present study was to investigate the influence of physical exercise on the permeability of the cellular membrane to enzymes. The following three experiments were conducted: 1. Running training: the effects of 10-week physical training (running over 5 km, 6 times/week) on both the activity and concentration of <gamma>-glutamyl transpeptidase (<gamma>GTP) in plasma were investigated on seven sedentary male students. After training the resting plasma <gamma>GTP concentration decreased to half, whereas the <gamma>GTP activity did not vary substantially. This suggests that after training the precursor form of <gamma>GTP did not appear in the plasma and that 'activator protein' appeared in the plasma, possibly due to a leakage from the tissues such as liver. 2. Prolonged exercise: Fifteen male Wistar rats were exercised by swimming until exhausted with a weight equal to 3 % of their body weight in water at 35゜C. Microsomal <gamma>GTP was studied in the liver cell fractions. In vivo and in vitro permeabilities for both <gamma>GTP activity and content were calculated by the following formulas:In vivo permeability (%)= (extramicrosomal fraction x 100 )/(tramicrosomal fraction + microsomal fraction ) andin vitro permeability (%) = ( hyposmotic condition )/(osmotic condition ) x 100The in vivo permeability of both <gamma>GTP activity and content was greatly enhanced after swimming, whereas the in vitro permeability did not change significantly. This indicates that acute exercise increases the permeability of the microsomal membrane of rat liver. 3. Swimming training: Ten male Wister rats were exercised by swimming to 3 h/day, five times/week for 10 weeks in water at 35゜C. After training both the in vivo and in vitro permeabilities-estimated by <gamma>GTP and content-of the membrane of the liver microsomes appeared to reduce, suggesting an increased stability of thr microsomal membrane.