Triclosan, an environmental pollutant from health care products, evokes charybdotoxin-sensitive hyperpolarization in rat thymocytes.

The effects of triclosan, an environmental pollutant from household items and health care products, on membrane potential and intracellular Ca(2+) concentrations of rat thymocytes were examined by a flow cytometry with fluorescent probes, di-BA-C(4) and fluo-3-AM, because triclosan is often found in humans and wild animals. Triclosan at a concentration of 3 μM decreased the intensity of di-BA-C(4) fluorescence, indicating the triclosan-induced hyperpolarization. The application of charybdotoxin, a specific inhibitor of Ca(2+)-dependent K(+) channels, and the removal of external Ca(2+) eliminated the triclosan-attenuation of di-BA-C(4) fluorescence. Furthermore, triclosan augmented the fluo-3 fluorescence under normal Ca(2+) condition, indicating that triclosan increased intracellular Ca(2+) concentration. These results suggest that triclosan induces membrane hyperpolarization by increasing intracellular Ca(2+) concentration that activates Ca(2+)-dependent K(+) channels. Since the change in membrane potential of lymphocytes influence cellular immune functions, triclosan may exert adverse actions on immune system in human and wild animals.