Effect of fibrin on arterial endothelial cells in vitro--an electron microscopic study

An interaction between fibrin and arterial endothelial cells was studied in vitro electron microscopically by the modified method of Warren et al. Microvilli and cytoplasmic processes attached to fibrin threads in an early period of fibrinolysis and fibrin threads showed fine fibrillar or granular appearance in the lysed areas. Dilatation of endoplasmic reticulum and increase in number of intracytoplasmic vesicles, mainly in the luminal side of endothelial cells, were noted in the endothelial cells in the lysed areas. Fibrinolytically active endothelial cells were observed in 38 out of 100 endothelial cells of the rat aorta. Therefore, were suggest that microvilli of endothelial cells might play an important role in release of plasminogen tissue activator from the endothelial cells, and a heterogeneity of the endothelial cells exists in the reactivity to fibrin.