Arteriosclerosis of the pancreas and changes in the islets of Langerhans of repeatedly bred rats.

Repeatedly bred male and female rats develop hyperglycaemia, hyperlipidaemia, hypertension, arteriosclerosis and age prematurely. The intensity of these degenerative changes parallels the number and frequency of breedings. The islets of Langerhans undergo progressive hyperplasia and β-cell degranulation with each successive breeding. The pancreatic arteries are especially prone to develop arterial lesions which consist of abnormal mucopolysaccharide accumulation, elastic tissue breakdown, fibrosis and calcification. With continued active breeding the islet degenerative changes and arteriosclerosis become aggravated and many animals exhibit acinar necrosis, pancreatitis and parenchymatous calcification. It is believed that reproductive activity activates the hypothalamic-pituitary-adrenal-gonadal axis releasing hormones which have a dynamic effect on protein, fat and carbohydrate metabolism. In addition, unusual metabolic demands during such phases as gestation and lactation also effect protein, fat and carbohydrate metabolism leading to β-cell degranulation or “exhaustion” of insulin reserve.