Ultrastructural characteristics of myocardial capillaries during physical exertion

In the model experiments with physical overloading of "trained" rabbits, that repeatedly terminated in death, it has been stated that ultrastructural changes of the myocardial blood capillaries can be manifested as a considerable increase of the endotheliocytic nuclei volume, swelling of the cytoplasmic matrix, an essential accumulation of pinocytic vesicles, or a rather significant decrease of their number in cytoplasm and as various combinations of the changes mentioned; this negatively influences hemodynamic and trophic functions of the capillaries. The changes of endotheliocytes can be characterized as submicroscopical bases of the transcapillary insufficiency. More manifested ultrastructural changes of the capillaries are noted in the left cardiac parts.