Alloxan diabetes in spontaneously hypertensive rats: gravimetric, metabolic and histopathological alterations

In order to investigate the combined effects of diabetes and hypertension on the pathogenesis of cardiovascular disease, adult male and female SHR rats which develop hypertension spontaneously were given a single, 10 mg or 15 mg/100 g body wt. injection of alloxan s.c. to induce moderate or severe diabetes. Insulin was deliberately withheld. Animals were examined by autopsy daily for 7 days post-alloxan and after 4 and 8 weeks. Mortality was high--only 52% of the males survived as against 80% of the females. Most deaths occurred on Day 5 and were associated with adrenal haemorrhage and hyperplasia, thymus galnd involution, fatty liver and marked hypotension despite elevated aldosterone levels. During the first week, corticosterone levels increased significantly in the male; in females they showed little change. After 4 weeks, the severly diabetic animals became emaciated and moribund; corticosterone and aldosterone levels fell to very low levels despite adrenal hyperplasia. The beta cells of the moderately diabetic animals eventually lost their ability to secrete insulin and these animals too became cachetic and moribund with concomitant elevation of lipid, glucose and BUN levels, as well as myocardial infarction, fatty liver, and generalized hyalin arteriolo-, arterio-, and nephrosclerosis. It is suggested that the combined hormonal and metabolic alterations of diabetes and hypertension reinforced one another in these spontaneously hypertensive rats, leading to intense stimulation of the hypothalamic-pituitary-adrenal system, the exacerbation of those cardiovascular degenerative changes known to be associated with uncontrolled diabetes or hypertension, eventual impaired adrenocortical steroidogenesis, hypotension and death.