Increase in number of annexin V-positive living cells of rat thymocytes by intracellular Pb2+

Abstract Lead is ubiquitous in our environment and lead poisoning is a major public health problem worldwide. In this study, to see if intracellular Pb 2+ induces the exposure of phosphatidylserine in rat thymocyte membranes, we have examined the effect of PbCl 2 on rat thymocytes treated with A23187 using a flow cytometer with appropriate fluorescent indicators under nominally-Ca 2+ -free condition. PbCl 2 at 1–30 μM dose-dependently induced the exposure of phosphatidylserine on outer membranes, associated with increasing the concentration of intracellular Pb 2+ . The potency of intracellular Pb 2+ to induce the apoptotic change in thymocyte membranes seems to be greater than those of intracellular Ca 2+ and Cd 2+ . Results suggest that intracellular Pb 2+ triggers apoptosis of rat thymocytes. This action of Pb 2+ may be one of mechanisms for the lead-induced changes in immunity.