Tri-n-butyltin-induced blockade of store-operated calcium influx in rat thymocytes

Tri-n-butyltin (TBT), one of environmental pollutants, disturbs intracellular Ca2+ homeostasis by increasing intracellular Ca2+ concentration ([Ca2+]i). Effect of TBT on oscillatory change in [Ca2+]i (Ca2+ oscillation) of rat thymocytes was examined using a laser microscope with fluo-3-AM in order to further elucidate the TBT toxicity related to intracellular Ca2+. The Ca2+ oscillation was completely attenuated by 300 nM TBT. Since store-operated Ca2+ channels are involved in the generation of Ca2+ oscillation, the action of TBT on an increase in [Ca2+]i by Ca2+ influx through store-operated Ca2+ channels was examined. The increase in [Ca2+]i by the store-operated Ca2+ influx was not affected by 3 nM TBT. However, TBT at 10 nM or more significantly reduced the increase in [Ca2+]i. It is likely that TBT attenuates the Ca2+ oscillation by reducing the Ca2+ influx through store-operated Ca2+ channels.