Acute arteriolar lesions of rat intestine caused by kidney extract.

Lysosomal fraction of renal cortical extract, which showed high renin activity, and equipressor dosis of synthetic angiotensin II amide were administered into one-hour nephrectomized rats. Sixty minutes after the sustained elevation of 20 mmHg in mean arterial pressure by each pressor substance, the rats were sacrificed and the intraperitoneal organs were fixed. Five minutes prior to the administration of each pressor substance ferritin solution, as a test substance for vascular permeability, was intravenously injected. Medial changes in the arterioles in the intestinal submucosa were observed by electron microscopy. In angiotensin II group early lytic lesions of the muscle cells were limited to the single muscle cells. Ferritin particles were rarely found in the media. In lysosomal fraction group the lytic lesions were more advanced. Some regions of the media exhibited focal loss of smooth muscle cells manifesting focal medial necrosis. Ferritin particles were distrubuted in some areas of the necrotic media. The results suggested that the kidney extract with high renin content contained substance(s) to produce both medial necrosis and plasma insudation into the media of the arterioles.