Abstract des Autors

The effects of pH, ammonia, divalent cations and 2,4-dinitrophenol (DNP; factor uncoupling the respiration of mitochondria) on the activity of ATPase in mitochondria isolated from rat skeletal muscle were studied. The obtained results have shown that the hydrolytic activity of mitochondrial ATPase was not affected by pH of the incubation medium as low as 6.4, existing in muscle cells following strenuous exercise, whereas Mg+2 and DNP brought about a fourfold increase of hydrolytic activity of that enzyme at pH 7.0 or 6.4. In contrast to that, Ca+2 effectively inhibited the hydrolytic activity of the enzyme complex at pH 6.4, and ammonia decreased the activity of Mg+2-stimulated ATPase by about 21 and 10% at pH 7.0 and 6.4, respectively. The effect of ammonia on DNP-uncoupled mitochondria was reversed, and a 35% increase of the activity was observed. Temperature appeared to be the most efficient factor increasing the hydrolytic activity of ATPase. The results may suggest that in experimental conditions simulating the post-exercise state of skeletal muscle cells, the mitochondrial ATPase activity is the resultant of the stimulating effect of temperature and Mg+2, and the inhibiting one of Ca+2 and ammonia. Verf.-Referat