The role of intracellular calcium in endothelin-1-induced proliferation of human lung adenocarcinoma cells SPC-A 1

Objective:To explore the role of intracellular calcium ([Ca2+]_i) in endothelin-1 (ET-1)-induced proliferation of human lung adenocarcinoma cells SPC-A 1 and the underlying mechanism. Methods: The mRNA transcription of ET-1 and ET receptor (ETR) were detected by reverse transcription-polymerase chain reaction (RT-PCR) and ET-1 and ETR protein expressions in SPC-A 1 cells were measured by Western blotting. Cell proliferation was measured by (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) MTT assay. Intracellular Ca2+ concentration was determined by Fura-2/AM fluorescent assay. Results: ET-1 and ET_AR and ET_BR were expressed in SPC-A 1 cells at mRNA and protein levels. ET-1 (10-15-10-8 mol/L) stimulated the proliferation of SPC-A 1 cells in vitro and increased [Ca2+]_i in a dose-dependent manner (P0.05). The effect of ET-1 (10-10 mol/L)on the proli-feration and [Ca2+]_i of SPC-A 1 cells was reversed by a highly selective ET-AR antagonist BQ 123 (10-7 mol/L, P0.05), but could not be reversed by a highly selective ET-BR antagonist BQ 788(10-7 mol/L, P0.05). Deletion of extracellular Ca2+ with edetic acid (EDTA, 0.4 mmol/L) or blockade of voltage-gated calcium channels with nifedipine (1 μmol/L) significantly inhibites ET-1-induced elevation of [Ca2+]_i and proliferation of SPC-A 1 cells. Conclusion: ET-1 stimulates cell proliferation and increased [Ca2+]_i by activation of ET-AR in SPC-A 1 cells. Ca2+ influx via voltage-gated calcium channel is the main mechanism for [Ca2+]_i elevation and cell proliferation.