Effect of solution of low pH on releases of beta-endorphin-like immunoreactivity and ACTH-like immunoreactivity from human gastric antral mucosa in vitro.

The presence of beta-endorphin-like and ACTH-like immunoreactivities (beta-EpLI, and ACTH-LI, respectively) in human gastric antral mucosa and their release were studied. beta-EpLI (14.1 +/- 4.8 ng/g wet weight) and ACTH-LI (11.1 +/- 1.2 ng/g wet weight) were detected in human gastric antral mucosa. The two activities gave similar curves for inhibition of human beta-Ep and ACTH on radioimmunoassay, respectively. On gel-filtration chromatography of a gastric antral extract, three components of beta-EpLI and two components of ACTH-LI were separated. When human gastric antral mucosa was incubated with a solution of pH 4.0 or pH 2.0, the release of beta-EpLI and ACTH-LI from the mucosa into the incubation medium increased 2.3-9.8-fold. However, incubation with 20 mM glucose or 20 mM amino acids did not have any effect on the release of beta-EpLI and ACTH-LI. These results indicate that beta-EpLI and ACTH-LI present in human gastric antral mucosa are released by direct action of a solution of low pH on the gastric antral mucosa.