Capillary endothelial morphometric profiles in fast and slow twitch muscle: alterations in response to anesthesia and electrical stimulation

Abstract

Recent investigations focusing on transcapillary exchange have correlated physiologic and ultrastructural findings in an effort to understand mechanisms associated with endothelial function. The vascular endothelium is permeable to water and macromolecules such as lipoproteins and plasma proteins. Plasmalemmal vesicles inside the endothelium are involved with the transport of substances. These vesicles can fuse on both endothelial fronts and they can form transendothelial channels by way of vesicular fusion. These ultrastructural alterations can increase the capillary endothelial surface area by a factor of 0.5-2.0. Recent studies suggest that endothelial permeability is modulated by the fusion of vesicles into clusters which may act as transendothelial channels. The density of vesicles differ from one tissue to another. Vesicle numbers are under physiologic control and have been reported to increase in lung capillaries in response to edema and hydrostatic pressure. Physiology and cell biology must be integrated in an effort to understand the complexity of endothelial function. Therefore, the purpose of this study was to compare the morphometric profiles of capillary endothelium response to anesthesia and electrical stimulation in two muscles of the rat hind limb, the capillary enriched slow-twitch soleus, and the low oxidative fast-twitch plantaris.