Cytotoxic actions of lidocaine at sublethal concentrations : A model in vitro experiment using rat thymocytes

In order to reveal some cytotoxic features of lidocaine, the effects of lidocaine at sublethal
concentrations (10 mM or less) on rat thymocytes were examined by the use of flow-cytometric
technique with fluorescent probes. Treatment with lidocaine at 3-10 mM for 1-3 hr
significantly increased intracellular Ca2+ and Zn2+ concentrations under normal condition.
After the removal of external Ca2+ and Zn2+, lidocaine still increased intracellular Ca2+ and Zn2+
concentrations, suggesting the lidocaine-induced release of intracellular Ca2+ and Zn2+.
Treatment with lidocaine at 0.3-1 mM for 24 hr significantly increased the populations of dead
cells and shrunken cells. Lidocaine at sublethal concentrations exerts some cellular actions
that are supposed to be linked to the cytotoxicity. The mechanism of lidocaine-induced cell
death varies in time- and concentration-dependent manners.