Changes in met-enkephalin and beta-endorphin contents in the hypothalamus and the pituitary in diabetic rats: effects of insulin therapy.
1. Immunoreactive (IR)-met-enkephalin and beta-endorphin contents in the hypothalamus and the pituitary were measured in alloxan-diabetic rats with or without insulin treatment. 2. Both IR-met-enkephalin and IR-beta-endorphin in the pituitary were substantially reduced in alloxan-diabetic rats 1 month after treatment. 3. Hypothalamic IR-beta-endorphin content was also significantly lower. 4. Gel-filtration chromatography showed that the peaks co-eluting with met-enkephalin precursor, met-enkephalin and beta-endorphin were lower in the pituitaries from the diabetic rats, whereas the peaks co-eluting with beta-endorphin precursor and beta-lipotropin were not. 5. In another experiment, the IR-beta-endorphin contents of the neuro-intermediate lobe and hypothalamus, but not the anterior lobe were significantly lowered in diabetic rats, whereas IR-met-enkephalin contents were significantly reduced in both the anterior and neuro-intermediate lobe. 6. All these changes were reversed by insulin treatment. 7. As a decrease in general protein synthesis could not explain the recorded changes, these results suggest a possible direct role of insulin in regulating the opioid peptide content of the hypothalamus and pituitary.
Tang
F
F
Department of Physiology, Faculty of Medicine, University of Hong Kong.
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002850:Chromatography, Gel; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000032:analysis / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism*; D007328:Insulin / Q000627:therapeutic use*; D008297:Male; D009929:Organ Size / Q000187:drug effects; D010902:Pituitary Gland / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin / Q000032:analysis / Q000378:metabolism*
D007328:Insulin; D004744:Enkephalin, Methionine; D001615:beta-Endorphin