MG2-DEPENDENCE OF VOLUME-SENSITIVE CL- CHANNELS IN HUMAN EPITHELIAL-CELLS( AND ATP)

During osmotic cell swelling whole-cell Cl- currents were recorded in cultured human small intestinal epithelial cells (Intestine 407). When intracellular ATP was depleted, swelling-induced Cl- currents were ab olished. Increases in intracellular free ATP enhanced the Cl- current in a concentration-dependent manner. The presence of intracellular fre e Mg2+ ions suppressed the current. Non-hydrolyzable ATP analogs (AMP- PNP and ATP gamma S), ADP, and GTP could substitute for ATP. Thus, it is concluded that ATP plays an indispensable role in activation of the volume-sensitive Cl- channel without hydrolysis and that intracellula r Mg2+ is an additional regulator for volume-sensitive Cl- channels in Intestine 407 cells.