Morphometric analysis of myocardial mitochondria in rats during adaptation to exercise.

Comparative morphometric studies of the mitochondria of muscle cells and of interstitial cells of rat hearts were carried out in order to obtain more information about changes in mitochondrial parameters during adaptation of the myocardium to physical training of different durations (45, 180, 360 hours of swimming) and intensities. On the basis of the results the authors conclude that the mitochondrial biogenesis of heart muscle cells occurs in dependence on the intensity of training at two morphometrically different stages. Some parameters of the mitochondria of the interstitial cells reacted in a manner similar to that of the muscle cells, but opposite reactions were also observed. The biogenesis of mitochondria and the absence of a decrease in the mitochondria/myofibrils ratio in muscle cells may be regarded as an improvement in cell metabolism in the training-induced hypertrophy of the rat heart.