Effects of hypertension and hypercholesteremia on the permeability of fibrinogen and low density lipoprotein in the coronary artery of rabbits. Immunoelectron-microscopic study.

In an attempt to elucidate the effects of hypertension and/or hypercholesteremia on atherogenesis, with special reference to permeation and deposition of fibrinogen and low density lipoprotein (LDL) in the coronary artery, we studied electron-microscopically the localization of fibrinogen and LDL. In the untreated control rabbits, fibrinogen was localized in the caveolae and vesicles of the endothelial cells and in very small amounts in the subendothelial spaces of the coronary artery. Hypertension or hypercholesteremia was related to an enhanced insudation of fibrinogen into the subendothelial spaces of the coronary artery. The insudation of fibrinogen seemed to have occurred by way of vesicular transport and, to some extent, by junctional transport. LDL was localized only in the caveolae and vesicles of the endothelial cells of the coronary artery in the untreated control rabbits. LDL was deposited in the subendothelial space of the hypercholesteremic rabbits, with or without hypertension. Despite the lack of clear-cut and direct evidence, the insudation of LDL into the intima appeared to be enhanced by way of vesicular transport.