Structural and functional characteristics of endothelial cells of vessels of the heart of newborn rats (immunohistochemical study)

The study is aimed to investigate the pattern of cytodifferentiation of developing endothelial cells (EC) of microcirculatory bed of the heart of newborn rats using light microscopy and immunohistochemical labeling of von Willebrand factor (vWF). Immunohistochemical study was carried out on Wistar rats on the postnatal day 1 (n=6). For the first time, EC of the developing vessels of the heart of newborn rats were found to be on different stages of cytodifferentiation. Most pronounced structural and functional maturity at this developmental stage was typical for EC of intima of aorta, coronary vessels, middle and small arteries and arterioles of the myocardium in the upper third of the ventricles. Endothelium of these vessels demonstrates strong vWF-immunoreactivity, while in the developing capillaries of the sinusoidal type of the subepicardial region and ventricular endocardium, the vWF-immunoreaction at this time period is still weak or absent. Morphological pattern and variability of sizes of vWF-immunoreactive granules of endothelium has been established. Signs of secretion in the EC were revealed. Synthesis, accumulation, and exocytosis of vWF are suggested to be associated with the degree of cytodifferentiation of EC.