Time course of arterial repair following endothelial denudation in the rat carotid artery. A morphometric study in Wistar and Sprague-Dawley rats.

Repair processes in the intima and media of the rat carotid artery were studied morphometrically for time intervals of up to 28 days after injury induced by air-drying. Air-drying injury included endothelial denudation as well as medial necrosis. Repair was most rapid between days 9 and 11 after injury as regards the increase in myointimal lesion size, the extent of repopulation of the media and re-endothelialization. After day 11, myointimal lesion size continued to increase until day 28. Medial repair, however, almost completely ceased at day 11, 25% of the inner media and 5% of the outer media remaining necrotic. At day 21, the vessels were almost completely re-endothelialized; however, even at day 28, about 10% of the middle of the vessel was still permeable to Evans Blue. The response of Sprague Dawley rats to injury differed from that of Wistar rats. Compared with Wistar rats, Sprague Dawley rats showed larger myointimal lesions, less medial necrosis and slower endothelial repair. It is suggested that the extent of medial necrosis and the speed of endothelial regeneration affect the arteriosclerotic response in rats.