Elevation of the intracellular Zn2+ level by 2-n-octyl-4-isothiazolin-3-one in rat thymocytes: an involvement of a temperature-sensitive Zn2+ pathway

High amounts of 2-n-octyl-4-isothiazolin-3-one (OIT), an antimicrobial, are found in wet polyvinyl alcohol towels with cooling properties. Although the diverse actions of OIT are of concern, information on its cellular actions is limited. In this study, we examined the effects of OIT on Zn2+ levels in rat thymocytes by flow cytometric analysis with FluoZin-3, and assessed the cytotoxicity of this agent. OIT (1-3 mu M) significantly increased the intensity of the FluoZin-3 fluorescence. Removal of extracellular Zn2+ almost completely inhibited the OIT-induced increase in FluoZin-3 fluorescence. Furthermore, the increase in OIT-induced FluoZin-3 fluorescence was attenuated at cold temperatures. The effect of OIT on the FluoZin-3 fluorescence was dependent on the transmembrane Zn2+ gradient. Based on our data, we concluded that OIT activates a temperature-sensitive, bi-directional Zn2+ pathway, resulting in alterations to the intracellular Zn2+ levels. Importantly, these changes are dependent on a transmembrane Zn2+ gradient. These results may provide insight into the cytotoxicity of OIT, because Zn2+ has physiological and pathological roles in cellular functions.