Two store-operated Ca²⁺ influxes with differential sensitivities to Zn²⁺ in mouse salivary gland acinar cells.

Abstract

In non-excitable cells, the underlying mechanism for Ca²⁺ influx is thought to be mediated by newly generated Ca²⁺ selective channels through the depletion of Ca²⁺ storage pools (store-operated Ca²⁺ influx: SOC). A unique SOC with high Ca²⁺ selectivity has been well studied in mast cells and the like, however, SOC appears to vary in cell types and play its role in cell specific manner. Here we studied SOC in fura-2 loaded mouse submandibular acinar cells with microfluorimetry. After depleting the Ca²⁺-stores with thapsigargin or a high concentration of ACh under Ca²⁺ free condition, we measured SOC signal by the readmission of Ca²⁺. The signal possessed two phases. That is, an initial large transient and the subsequent long-lasting phase. External Zn²⁺ inhibited the former but not the latter. External Ni²⁺ or excess of outside K⁺ (90mM) markedly reduced both. The results suggest that two SOCs, differentiable by the divalent cations, exist in salivary gland acinar cells. [Jpn J Physiol 55 Suppl:S70 (2005)]