Luminal alkalinization in the intestine of the goby

The rate of luminal alkalinization in vitro by Gillichthys mirabilis posterior intestine as measured by a manual pH stat technique was 0.70±0.05 μEquiv/cm² h; acidification of the mucosal medium was never observed. The rate of HCO₃^- secretion (J^HCO₃) was reduced by ouabain, serosally-applied DIDS, removal of serosal HCO₃^- and replacement of media Cl^- with gluconate. HCO₃^- secretion was enhanced replacement of Cl^- with isethionate and unaffected by mucosal DIDS, furosemide or acetazolamide. J^HCO₃ was reduced at mucosal pH above or below 7.5. These results support active HCO₃^- secretion via a Cl^-/HCO₃^- exchange mechanism on the basolateral membrane and a conductive exit pathway for HCO₃^-, H⁺ or OH^- on the apical membrane.