β-endorphin concentrations in the hypothalamus, pituitary and plasma of streptozotocin-diabetic rats with and without insulin substitution therapy

Abstract

The concentrations of β-endorphin like immunoreactivity (β-END) in the hypothalamus, pituitary and plasma were studied in rats of either sex, one month after induction of diabetes by single iv injection of streptozotocin. As controls, both normal and undernourished rats, weight-matched with diabetic rats, were used. Diabetic male and female rats had a marked depletion of β-END stores in the hypothalamus and neurointermediate lobe (NIL) but not in the anterior pituitary. Depletion of β-END was reversed to normal by insulin replacement therapy. Severe undernourishment was not as effective as diabetes to reduce β-END stores in the hypothalamus and NIL. A significant reduction of β-END was observed only in the NIL of undernourished female rats. Plasma β-END and β-lipotropin (β-LPH) concentrations were not significantly altered in diabetic rats. These results indicate that the lack of insulin may affect β-END synthesis in the hypothalamus and NIL.