The ultrastructural characteristics of the capillary endothelium from different sections of the canine heart

: Electron microscopy of auricular and ventricular endothelial blood capillary cells (EC) was performed for two groups of dogs, both at normal body temperature (control) and after cooling up to 28-30 degrees C. Cell organelles involved in synthetic processes were developed more in the auricular EC, and the number of specific granules in these exceeded that in organelles of the ventricular EC. The ventricular transport structures were more numerous and more diverse compared to the auricular ones. These subcellular features retained under hypometabolism induced by cooling. Both common (reduction of organelles involved in synthesis) and different ultrastructural responses to cooling were observed in auricular and ventricular endothelial cells. It is established that under hypothermia the ratio between "dark" and "light" granules in auricular EC remains invariable. At the same time, in ventricular EC the share of "light" granules in this ratio was 4 times more than in the control group. These results suggest an existence of ultrastructural differentiation of auricular and ventricular EC.