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.