Ultrastructure of the renal arterial bifurcation of rabbits

Abstract

Intimal thickenings at renal artery bifurcations of 30 rabbits were studied ultrastructurally. After localization of intimal pads, the forks were cut on several planes. No microthrombi were observed at the fork but the endothelium of the fork and stem contained bundles of cytoplasmic fibrils incorporating dense bodies like those in smooth muscle cells. The densities were at times arranged as cross striations with a fairly regular periodicity. The internal elastic lamina external to the pads appeared thinned or deficient with much collagen and fibrillary elastica between the strata of muscle cells in the intimal thickenings. The intimal pads contained quantities of cell debris seemingly derived from both endothelium and muscle. Degenerate and undifferentiated cells were observed in the intimal pads and calcification but rarely. Intimal pads are apparently sites of enhanced degeneration of endothelium, smooth muscle cells and elastic tissue.