DIFFERENTIAL-EFFECTS OF TAMOXIFEN AND I- ON 3 DISTINGUISHABLE CHLORIDE CURRENTS ACTIVATED IN T84 INTESTINAL-CELLS

The whole-cell mode of the patch-clamp technique has been used to moni tor ionic currents in T84 colonic carcinoma cells. The cells were stim ulated by either a cAMP cocktail, ionomycin or hypotonicity. Sizeable currents with distinct kinetics were observed after the stimulation wi th the different agonists. These kinetically distinct Cl- currents als o presented a differential sensitivity to the anti-oestrogen Tamoxifen and to the halide I-. Tamoxifen only inhibits the volume activated CI - current without affecting the other two. Substitution of extracellul ar CI- by I- shifted the reversal potential towards more negative valu es both in the hypotonicity and ionomycin activated CI- currents. The cAMP activated current responded to the CI substitution by T with a bl ockade of both outward and inward currents, in addition to the displac ement of the zero current level towards positive values. Thus, the use of these two simple tools, I- and tamoxifen, allows the distinction o f CI- channels in epithelial cells.