Ultrastructure of coronary arteries and myocardium in experimental hypertension

Abstract

The ultrastructure of coronary arteries and myocardium has been examined after 1–4 weeks of experimental hypertension produced in Wistar-Kyoto rats by unilateral renal artery constriction. Upon sacrifice blocks of ventricular myocardium were processed for light and electron microscopy. Two types of medial necrosis are observed in epicardial arteries: one involving elongated smooth muscle cells throughout the media and the other localized to the outer layers of the vessel wall. Some of the epicardial and intramyocardial arteries exhibit hyperplastic lesions characterized by smooth muscle cells in the subendothelial space. Medial smooth muscle cells of small intramyocardial arteries also exhibit contraction, fragmentation and necrosis. Plasma, cells and fibrin accumulate in the subendothelial space of intramyocardial arteries. Discrete areas of myocardial injury of variable severity are present in the subendocardium of the left ventricle. The vascular lesions in epicardial and intramyocardial arteries are related to the severity of blood pressure elevation and the vasoconstrictor actions of angiotensin II, while the foci of myocardial damage are consistent with ischemic or anoxic injury.