Hypertensive arterial disease and atherogenesis. Part. 1. Intimal changes in the old, spontaneously hypertensive rat (SHR).

The histological, ultrastructural and permeability aspects of the intima in 60 70-week-old spontaneously hypertensive (SHR) and Wistar Kyoto normotensive (WK) rats were studied and compared. The intima of aorta, coronary and renal arteries was unequally thickened owing to the smooth muscle cell (SMC) migration and proliferation, blood cell immigration and endothelial cell activation. The present work describes intimal changes that may act as potential atherogenic factors, i.e. hyper-reactivity of endothelial cells; decreased thinness of endothelial cell periphery; reduced intercellular junction pathways; increased quantity of basement lamina and glycosaminoglycan subendothelial material; platelet and monocyte-macrophage infiltration; widened fenestrae in the internal elastic lamina, and smooth muscle cell migration and proliferation. These changes might possibly be able to reduce the atheroresistance of this species by reducing the barrier function, increasing the trapping effect and stimulating smooth muscle cell proliferation and fibrogenesis. They are believed to promote the development of arterial lipidosis when hyperlipemia is an added risk factor.