Appearance of grossly-visible aortic sclerosis in breeder rats: reconfirmation and up-date, 1957-1981.

Multiparous Sprague-Dawley rats were killed at 7, 14, and 21 days of gestation, at parturition, after 7, 14 and 21 days of lactation, and at 7 and 14 days post-weaning of their fourth reproductive cycle. Grossly visible aortic sclerosis appeared and became progressively more severe during gestation, parturition, and early lactation. Although some of the female breeders had no detectable, grossly-visible aortic sclerosis, all of the 4-time breeders had microscopic aortic sclerosis. Progressive deterioration of the aortic elastic tissue and ground substance was particularly prevalent during the gestation and lactation phases. Calcification and cartilaginous metaplasia appeared during the post-weaning phase. Virgin control rats, equal in age to the 4-time breeders, were completely free of arterial disease. It is believed that abnormal activity of the hypothalamic-pituitary-adrenal axis in association with repeated breeding conditions these animals toward premature arteriosclerosis.