Studies on the role of opiate peptides in two forms of genetic obesity: ob/ob mouse and fa/fa rat.
Recent reports have indicated that genetically obese hyperinsulinemic mice (ob/ob) and Zucker rats (fa/fa) compared with their lean controls have elevated levels of pituitary and plasma B-endorphins, opiates that can stimulate insulin secretion. In this study we have measured opiate levels by a radio-receptor assay in gastro-intestinal tissues and pancreas in ob/ob and fa/fa animals and their controls. Ob/ob mice showed significantly higher levels than control mice (+/+) in most gastro-intestinal tissues and pancreas. Levels in fa/fa rats did not differ from their controls. Radioimmunoassay of pancreas for B-endorphins, revealed higher levels in ob/ob vs +/+ mice, while there was no difference in the obese and lean rats. Fasting tended to decrease gastro-intestinal opioids in mice, while B-endorphin levels rose. It is concluded that opiates may play a significant role in the obesity of the ob/ob mouse and that this genetic obesity differs from that in Zucker rats.
D000818:Animals; D002845:Chromatography; D004064:Digestive System / Q000032:analysis; D004723:Endorphins / Q000032:analysis / Q000502:physiology*; D004743:Enkephalin, Leucine / Q000032:analysis; D005215:Fasting; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D008297:Male; D051379:Mice; D008820:Mice, Obese; D009270:Naloxone / Q000494:pharmacology; D009765:Obesity / Q000503:physiopathology*; D010179:Pancreas / Q000032:analysis; D011863:Radioimmunoassay; D011869:Radioligand Assay; D051381:Rats; D011924:Rats, Zucker; D014018:Tissue Distribution; D014020:Tissue Extracts / Q000032:analysis
D004723:Endorphins; D007328:Insulin; D014020:Tissue Extracts; D009270:Naloxone; D004743:Enkephalin, Leucine