Importance of amino acid uptake and decarboxylation in gastrin release from isolated G cells

Abstract

Studies of various species have demonstrated that the postprandial rise in serum gastrin levels is primarily attributable to the proteinaceous substances ingested^1–5. Although it is generally assumed that dietary amino acids are the primary stimulants of gastrin release, evidence supporting this notion based on experiments in vivo has been conflicting and unconvincing^6–10. We have investigated the role of amino acids as stimulants of gastrin release using a preparation of isolated rodent gastrin-containing G cells^11,12. We report here that the ability of an amino acid to stimulate gastrin release in vitro is directly correlated with its lipid solubility, the aromatic and long chain aliphatic amino acids being the most potent. In addition, we provide evidence that amino acid decarboxylation may be a necessary step in gastrin release as inhibitors of decarboxylase activity abolished amino acid-induced gastrin release, and amines, the decarboxylated derivatives of amino acids, were potent stimulants of hormone secretion in vitro. Thus, the uptake and decarboxylation of amine precursors may be a functionally important property of cells belonging to the APUD (amine precursor uptake and decarboxylation) class of endocrine cells.