Abstract

It has previously been demonstrated that met-enkephalin, and endogenous opiate, stimulates gastric acid secretion in man, while naloxone inhibits meal-stimulated acid secretion. In seven healthy subjects the opiate receptor antagonist naloxone was infused in a dose of 10 microgram/kg/h during stimulation of gastric acid secretion with pentagastrin 100 ng/kg/h and met-enkephalin 0.1 microgram/kg/h. Naloxone had no effect on pentagastrin-induced acid secretion, whereas met-enkephalin-induced acid secretion was completely abolished in both studies without affecting serum gastrin levels, suggesting that the acid inhibitory effect of naloxone is specifically directed towards met-enkephalin-induced acid secretion. The results support the assumption that met-enkephalin participates in the physiological stimulation of gastric acid secretion.