Histochemical demonstration of increased adrenomedullary catecholamine secretion in repeatedly bred arteriosclerotic rats.

Male and female, Sprague-Dawley rats were subjected to repeated breeding. When the female breeders had completed 4 closely-spaced pregnancies and had suckled 5 to 10 young after each pregnancy, the breeder rats were killed along with male and female virgin rats of the same age (controls). Male breeders developed microscopic aortic sclerosis (21/24), female breeders manifested grossly visible aortic sclerosis (18/24) ranging from minimal to severe degree, and the remaining females (6/24) had microscopic aortic sclerosis. Virgin rats were free of arterial disease. The arterial lesions consisted of copious subintimal and medial mucopolysaccharide pooling, subintimal fibrosis, elastolytic and intense calcific and cartilaginous alterations. The adrenal medullae of the arteriosclerotic breeder rats reacted positively to AgNO3-glutaraldehyde which demonstrates the presence of catecholamines, e.g., noradrenaline and adrenaline. The intensity of the histochemical reaction parallel the severity of aortic sclerosis. The medullary cells of female breeders were hyperplastic and pleomorphic. Pheochromocytomas were found in female breeders with the most advanced aortic sclerosis. It is suggested tht overactivity of the adrenal cortico-medullary axis contributes to the pathogenesis and morphologic characteristics of the arteriosclerosis, accelerated aging, and the Cushing's disease-like spectrum of degenerative changes which develop spontaneously in repeatedly-bred rats.