Modulation of acid secretion from enriched guinea pig parietal cells by opioid receptors

Membrane fragments of isolated cells from guinea pig gastric mucosa, enriched to 65% parietal cells, bind with high affinity the opioid peptide 3H-D-Ala2-D-Leu5-enkephalin (3H-DADLE). Binding was saturable and reversible. Scatchard analysis revealed a second binding site with low affinity but high capacity. Acid secretion by isolated, enriched parietal cells was determined by means of 14C-aminopyrine uptake. Basal acid secretion was not influenced by DADLE but that stimulated by histamine was further augmented by the enkephalin analog. This potentiating effect was prevented by the opioid antagonist naloxone. The present data provide for the first time evidence that gastric acid secretion is modulated by an opioid mechanism probably located on the parietal cell.