Surface topography of mitral valve endothelium from diet-induced, hypercholesterolemic rabbits.

Mammalian, cardiac endothelium has a surface topography that is characterized by plasmalemmal microappendages, nuclear bulges and ruffled cellular margins. SEM of the endothelial population over the two surfaces of the anterior cusp (leaflet) of the rabbit mitral valve revealed a very pleomorphic topography. The atrial and ventricular surfaces of the cusp displayed differences in microappendage population, cell density, nuclear contour and surface reactivity to Ruthenium Red and Concanavalin A. Comparative studies of similar populations from diet-induced hypercholesterolemic rabbits suggested an enhanced endothelial permeability as observed by an increase in cytoplasmic vesicles containing RR or Con A and by their intercellular passage into the subendothelium. Concomitant with these changes were disproportionate responses in the surface reaction of the carbohydrate cell coat (glycocalyx). The endothelial cells over the ventricular surface of the anterior cusp displayed the most dramatic changes with the appearance of numerous microappendages and intercellular fenestrations, the loss of RR and Con A surface reaction and the engorgement of the adjacent intima with foam-like cells containing the surface markers. Such surface responses appeared to precede or accompany alterations in endothelial integrity which suggests the importance of the blood-endothelial interface in the maintenance of the vascular wall.