title: Potassium-dependent chloride and water transport across the seawater eel intestine.
abstract: 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.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism*; D004524:Eels / Q000502:physiology*; D007413:Intestinal Mucosa / Q000502:physiology; D007422:Intestines / Q000502:physiology; D008871:Microvilli / Q000502:physiology; D011188:Potassium / Q000502:physiology; D012964:Sodium / Q000502:physiology; D014867:Water / Q000378:metabolism; D014882:Water-Electrolyte Balance
chemical_list: D002712:Chlorides; D014867:Water; D012964:Sodium; D011188:Potassium