Energy sources for gastric secretion: substrates

Abstract

A thorough study of the utilization of exogenous and endogenous substrates seemed to be a prerequisite to studying the effects of adenosine-3[image], 5[image]-phosphate on the metabolism of amphibian gastric mucosa in vitro. Water-soluble salts of short-and medium-chain fatty acids and ketones stimulated acid secretion and respiration. Lesser stimulation was produced by long-chain fatty acids complexed to albumin. Amino acids and intermediates of glycolysis did not affect acid secretion or respiration except for a small enhancement by pyruvate. However, exogenous glucose and pyruvate inhibited glycogen breakdown and increased lactic acid formation. The principal limitation to carbohydrate utilization appears to lie somewhere in the steps whereby pyruvate is converted to either acetyl-CoA or oxalacetate. Histamine enhanced glycogenolysis in mucosa incubated in chloride solutions but not in glucuronate solutions, showing that utilization of endogenous glucose contributed directly to the secretory process. The lipid content of serum and mucosa constituted a significant source of energy. Mucosal triglyceride and glycogen content decreased with incubation. The respiratory quotient varied between 0.7 and 1.0 in different mucosae.