Sodium and Chloride Transport in the Lizard Duodenum : Physiology

概要

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The mechanisms by which Na and Cl ions are transported across the duodenal epithelium of the lizard Gallotia galloti were studied under voltage-clamped conditions. The lizard duodenum actively absorbed sodium and chloride with a ratio of approximately 2:1. In the absence of sodium, the short-circuit current (Isc) and net chloride flux (J^<Cl>_<net>) were abolished. In the absence of chloride, the net sodium flux (J^<Na>_<net>) was halved but the short-circuit current (Isc) was not changed significantly. Treatment with acetazolamide, amiloride, or disulfonic stilbene (DIDS) abolished the net chloride flux almost completely, whereas the Isc was not changed significantly. When ouabain was added to the serosal side, the short-circuit current and net fluxes of sodium and chloride were abolished. From an analysis of the effects of these inhibitors, a plausible model was developed to explain the characteristics of the sodium and chloride transport. It is proposed that the entry of sodium into the cell across the luminal membrane occurs via two pathways. A part of the Na^+ entry occurs through the Na^+/H^+ antiporter and a part through an electrogenic pathway. The entry of Cl^- across the apical membrane occurs through the Cl^-/HCO_3^- antiport. Chloride seems to exit the cell by a diffusional process.
社団法人日本動物学会の論文
1989-08-15