Intracellular chloride activities in rabbit gallbladder: direct evidence for the role of the sodium-gradient in energizing "uphill" chloride transport.
Intracellular chloride activities, (Cl)c, in rabbit gallbladder were determined by using conventional (Kcl-filled) microelectrodes and Cl-selective, liquid ion-exchanger, microelectrodes. The results indicated that in the presence of a normal Ringer's solution, (Cl)c averages 35mM; this value is 2.3 times that predicted for an equilibrium distribution across the mucosal and baso-lateral membranes. On the other hand, when the tissue is bathed by Na-free solutions, (Cl)c declines to a value that does not differ significantly from that predicted for an equilibrium distribution. These results, together with those of Frizzell et al. (J. Gen. Physiol. 65:769, 1975) provide, for the first time, compelling evidence that (i) the movement of Cl from the mucosal solution into the cell is directed against an electrochemical potential difference (23mV); and (ii) this movement is energized by coupling to the entry of Na down a steep electrochemical potential difference. Finally, our data suggest that (i) Cl exit from the cell across the basolateral membrane may be coupled to the co-transport of a cation or the countertransport of an anion; and (ii) the mechanism responsible for active Na extrusion from the cell across the baso-lateral membrane is rheogenic (electrogenic), and is not the result of a neutral Na-K exchange.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D005260:Female; D005704:Gallbladder / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D009092:Mucous Membrane / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology
D002712:Chlorides; D012964:Sodium