Diabetes induced by streptozocin results in a decrease in immunoreactive beta-endorphin levels in the pituitary and hypothalamus of female rats

Abstract

Immunoreactive beta-endorphin (IR-BE) was measured by radioimmunoassay in the anterior pituitary (AP), neurointermediate lobe of the pituitary (NIL), and hypothalamus of female rats 4 wk after being made diabetic by a single injection of streptozocin (STZ). STZ-induced diabetes resulted in a significant reduction in the content and concentration of IR-BE in the AP and the content of IR-BE in the hypothalamus. Total hypothalamic protein was also significantly diminished. IR-BE levels in the NIL were unchanged. Column chromatography indicated that the reduction in IR-BE in the AP of the diabetic female rats represented a decrease in peptides that co-eluted with beta-endorphin and beta-lipotropin. In the hypothalamus, the reduction in IR-BE was represented solely by a decrease in a peptide co-eluting with beta-endorphin. Beta-lipotropin was not detectable in the hypothalami of control or diabetic female rats. These results suggest that, in the rat, diabetes may produce alterations in the mechanism(s) that regulate endogenous opiate levels in the pituitary and hypothalamus.