Chloride-stimulated sulfate efflux in Ehrlich ascites tumor cells: evidence for 1:1 coupling.
The kinetics of Cl-SO4-(2) exchange in Ehrlich ascites tumor cells was investigated in an attempt to determine the stoichiometry of this process. When tumor cells, equilibrated in Cl--free, 25 mM SO4-(2) medium are placed in SO4-(2)-free, 25 mm Cl-medium, both the net amount and rate of Cl-uptake far exceeds SO4-(2) loss.. Addition of the anion transport inhibitor SITS (4-acetamido-4,-isothiocyano-stilbene-2,2'-disulfonic acid) greatly reduces sulfate efflux (97%), but has no measurable effect on chloride uptake. Addition of furosemide, a Cl-transport inhibitor, reduces chloride uptake 94% but is without effect on sulfate efflux. These findings suggest that a chloride permeability pathway exists distinct from that utilized by SO4-(2). SITS, when added to furosemide treated cells, further reduces chloride uptake as well as inhibiting sulfate efflux, and under these experimental conditions, a linear relationship exists between SITS-sensitive, net chloride uptake and sulfate loss. The slope of this line is 1.05 (correlation coefficient = 0.996) which suggests the stoichiometry of Cl-SO4-(2) exchange is 1:1. Assuming a 1:1 stoichiometry, measurement of the initial chloride influx and initial sulfate efflux indicate that 92% of net chloride uptake is independent of sulfate efflux. Taken altogether, these results support the contention that the tumor cell possesses a permeability pathway which facilitates the exchange of one sulfate for one chloride. Under conditions where anion transport is not inhibited, this coupling is obscured by a second and quantitatively more important pathway for chloride uptake. This pathway is SITS-insensitive, although partially inhibited by furosemide.
D000818:Animals; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D004579:Electron Transport / Q000187:drug effects; D005665:Furosemide / Q000494:pharmacology; D008297:Male; D051379:Mice; D013267:Stilbenes / Q000494:pharmacology; D013431:Sulfates / Q000378:metabolism*
D002712:Chlorides; D013267:Stilbenes; D013431:Sulfates; D005665:Furosemide