Cl⁻ regulation of Ca²⁺ entry in rat submandibular acinar cells

Abstract

In rat submandibular acinar cells, the effects of intracellular Cl⁻ concentration ([Cl⁻]_i) on intracellular Ca²⁺ concentration ([Ca²⁺]_i) were examined. ACh evoked a biphasic increase in [Ca²⁺]_i, that is, an initial transient phase followed by a sustained phase. The initial transient phase is induced by a Ca²⁺ release from the intracellular stores and the sustained phase is maintained by a Ca²⁺ influx from the extracelluar solution, which is the so-called store-operated Ca²⁺ entry. In present study, application of Cl⁻ free solution replaced Cl⁻ by NO₃⁻ increased the sustained [Ca²⁺]_i) level and addition of Gd³⁺ to the Cl⁻ free solution decreased the [Ca²⁺]_i. In the resting state without ACh stimulation, application of Cl⁻ free solution increased [Ca²⁺]_i, suggesting that [Cl⁻]_i decrease activated non-store-operated Ca²⁺ entry. The sustained [Ca²⁺]_i) level increased when Cl⁻ influx was inhibited by an Na+/K+/2 Cl⁻ cotransporter blocker, BMT (bumetanide). These experimental data suggested that [Cl⁻]_i) decrease activated Ca²⁺ entry. When NPPB (5-nitro-2-(3-phenylpropylaminno)-benzoic acid), Cl⁻ channel blocker was applied the sustained [Ca²⁺]_i) level decreased, suggesting that [Cl⁻]_i) increment inhibited Ca²⁺ entry. In conclusion, the present study suggests that [Cl⁻]_i) regulates Ca²⁺ entry pathways which involve store-operated Ca²⁺ channels and non-store-operated Ca²⁺ channels in rat submandibular acinar cells. [J Physiol Sci. 2008;58 Suppl:S210]