VOLUME-INDUCED CHLORIDE TRANSPORT IN HT29 CELLS STUDIED BY X-RAY-MICROANALYSIS

Ion transport mediated by osmotically induced chloride channels in HT2 9 cells was investigated by X-ray microanalysis of cell cultures. The cells were cultured on cellulose nitrate filters, and exposed to isoto nic, hypotonic, or hypertonic solutions. Then the NaCl-rich medium was removed by rinsing the cells with a washing fluid, the cells were fro zen, freeze-dried, and analyzed. As washing solutions, distilled water , ammonium acetate, or mannitol (the latter two at different concentra tions) were used. No major effects of the composition of the washing f luid was noted, except for mannitol, which left remnants that caused a n apparent decrease in the intracellular elemental concentrations. In response to exposure to hypotonic solution (modified Krebs Ringer's bu ffer, KRB, with 90 mM NaCl), the cells lost Cl, K, and Na. On the othe r hand, exposure to hypertonic solution (modified KRB, 290 mM NaCl) ca used an increase of the intracellular concentrations of Na and Cl and a decrease in K. In the presence of chloride channel blockers, chlorid e efflux induced by exposure to hypotonic medium was inhibited. This c hloride efflux was also inhibited in the absence of extracellular calc ium, indicating that the process is Ca2+ dependent. (C) 1998 Wiley-Lis s, Inc.