Sequential ultrastructural changes of arteries in rats induced by restrained stress.

Single and repeated restrained stresses in rats were conducted as a model for evaluating sequential changes of gastric submucosal arteries evoked by stressful stimuli with an emphasis on medial alterations. By single restrained stress, three distinct acute changes of the media were found after a short time of the stress-withdrawal; (1) focal cytoplasmic necrosis, (2) fibrin insudation, and (3) leukocyte migration. These acute lesions were readily healed within 20 days without cellular increase or fibrous thickening of the intima. When the stress was repeated over a long period of time, medial smooth muscle cells showed marked degenerative changes ("atrophy with moth-eaten structure") with an increase of granular cell debris and basement membrane-like materials. The results suggest that angiopathic effects of stresses may be attributed to the unsuited responsiveness of small artery to vasospasm and its sequential hemodynamic derangements.