Immunoreactive α melanocyte stimulating hormone, its distribution in the gastrointestinal tract of intact and hypophysectomized rats

Abstract

The presence of immunoreactive α melanocyte stimulating hormone (IαMSH) was investigated in both mucosal and muscular layers of the various areas of the gastrointestinal tract. IαMSH was present in both layers in all areas of the gastrointestinal tract but the esophageal mucosa and muscularis in saline extracts. The highest concentrations were found in the duodenum. Hypophysectomized males tended to have higher content than intact males. There was no difference between intact estrogen-primed females and hypophysectomized females up to 1 month post hypophysectomy in any area. The tract of 3 month hypophysectomized females showed lower levels than the intact estrogen-primed females in 5 areas; however, in similar groups of 3 month hypophysectomized females which were estrogen primed, 8 of the 10 areas contained more IαMSH than the intact estrogen-primed females. Acid extracts from female rats during the estrous cycle showed no cycle-dependent differences. Comparison of acid and saline extracts showed an absence of IαMSH in gastric tissues and a decrease in the duodenal muscularis in acid extracts but no consistent differences were found in other areas. These results suggest that the IαMSH found in the gastrointestinal tract is not of pituitary origin but may be produced in the gastrointestinal tract. The induction of increased content by estrogen priming in hypophysectomized rats suggests that estrogen priming may induce production. The absence of IαMSH in acid extracts of the stomach suggests that a difference in distribution of pro-opio-cortin products may exist in the gastrointestinal tract.