Summary
Simultaneous measurements of net ion and water fluxes and transepithelial potential difference (PD) were made in the stripped intestine of the seawater eel, and it was examined whether Cl− was driven following electrochemical gradient for Na+ across the brush border membrane of the epithelium or not. When mucosal Na+ was completely replaced with K+, while the serosa was being bathed with normal Ringer's solution, net Cl− and water fluxes were maintained as high as those in normal Ringer's solution. After serosal Na+ was completely replaced with choline+ while the mucosa was being bathed with Na+-free KCl Ringer's solution, 80% of the original Cl− and water fluxes still persisted, indicating significant Na+-independent Cl− and water transport. These results are against a hypothesis that Cl− is driven by electrochemical gradient of Na+ across the brush border membrane. The Na+-independent Cl− and water fluxes were a saturable function of mucosal K+ concentration, suggesting K+-dependent Cl− and water transport. A possible mechanism of Cl− transport is discussed in relation to K+ transport. On the other hand, a good correlation was observed between the net Cl− and water fluxes. This suggests that water transport depends on Cl− transport system; NaCl and/or KCl cotransport.
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Ando, M. Potassium-dependent chloride and water transport across the seawater eel intestine. J. Membrain Biol. 73, 125–130 (1983). https://doi.org/10.1007/BF01870435
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DOI: https://doi.org/10.1007/BF01870435