Effect of single exhaustive swimming on mitochondrial enzyme activities in rat myocardium

The present work is a continuation of our studies on mitochondrial functions and enzyme activities after acute exhaustive swimming in liver and myocardium. In rat heart mitochondria the activities of SDH, cytochrome oxidase and ATPase (DNP-stimulated) increase after swimming and remain at that level until the end of the 22-hour rest period studied. The enzyme complexes--rotenone-sensitive NAD. H-cytochrome c-reductase and succinate-cytochrome c-reductase--decrease their activities in both experimental groups. The reduced activity of these two enzymes is determined by changes in this part of the respiratory chain which occur after the incorporation of DCPIP in the oxidation-reduction processes. The marker enzyme of the outer mitochondrial membranes--rotenone-insensitive NAD.H-cytochrome c-reductase--reveals unchanged activity after swimming and a 22-hour period of rest. The different changes in the activities of enzymes with different localization and organization in heart mitochondria are explained by disorganization of the inner membranes after exhaustive swimming, which could induce both activation of some enzymes and inhibition of others. The effect of certain factors during muscle exercise which could cause the established structural and functional changes in the mitochondria is discussed.