Effects of amino acids on chloride transport in Aplysia intestine

This investigation was principally undertaken to examine the mechanism by which organic solutes (amino acids) stimulate chloride transport across the Aplysia californica intestine. Isolated intestine, mounted between identical oxygenated seawater solutions, maintained stable transmural potential differences (serosa negative) and short-circuit currents for several hours at 25 degrees C. The addition of glycine to the mucosal solution stimulated rapid sustained increases in these electrical characteristics. The change in short-circuit increased curvilinearly with increasing concentrations of mucosal glycine. Mucosal glycine stimulated transmural potential difference and short-circuit current after mucosal phlorizin had partially inhibited D-glucose stimulation of the electrical characteristics. Mucosal glycine enhanced the transmural electrical characteristics. Mucosal glycine enhanced the transmural electrical characteristics after serosal ouabain had abolished them. The major portion of the amino acid-induced short-circuit current was carried by a net, active, chloride transfer from mucosa to serosa as determined by flux measurements. These results suggest that the amino acid-induced effect on chloride transport is mediated by a common mucosal membrane carrier for both sodium and the amino acid.