THE DEVELOPEMENT AND HEALING OF ARTERIAL LESIONS IN HYPERTENSIVE RATS WITH BILATERALLY CONSTRICTED RENAL ARTERIES

Abstract

The morphogenesis and healing process of arterial lesions in hypertensive rats with bilaterally constricted renal arteries were studied morphologically.1. Arterial fibrinoid degeneration was seen in almost all organs, with special predirection in the mesentery, pancreas, right ventricle of the heart, and pretty often in the brain causing intracerebral massive hemorrhage. The lesion closely resembled to the so-called angionecrosis which is the direct cause of hypertensive intracerebral massive hemorrhage in human beings.2. In the early stage, intimal edema, medial edema together with degeneration of smooth muscle cells, and adventitial cellular reaction were observed. Fibrinoid substance subsequently appeared in the intima. These lesions were considered to be ascribed to increased vascular permeability resulting from hypertension and other causal factors.3. Rats survived for long period often revealed cellulofibrous intimal thickening as well as fibrinoid degeneration.4. Constricting clamps were removed from the renal arteries after 517 weeks, at which time the fibrinoid degeneration was proven by biopsy of the mesenteric arteries.Then the blood pressure fell rapidly to normal level, increase of vascular permeability ceased, and no further cerebral hemorrhage occurred.Histological study revealed two healing processes : a) complete disappearance of previously deposited fibrinoid substance with minimum intimal cell proliferation, and b) the healing process with remarkable cellulofibrous intimal thickening.The morohogenesis of the cellulofibrous intimal thickening was further studied by means of electronmicroscopical and autoradiographical methods. These revealed that the endothelial cells of arteries play an outstanding role in the developement of the intimal cell proliferation.The experimental results suggested that if the causes of angionecrosis are removed, it will be healed without residual change or healed with a kind of arteriosclerotic lesion.