The effect and mechanism of endothelin-1-induced intracellular free calcium in human lung adenocarcinoma cells SPC-A1.

Abstract

Endothelin-1 (ET-1) is a potent mitogen involved in cell growth in human lung adenocarcinoma cells SPC-A1. The increase in intracellular free calcium ([Ca(2+)]i) plays a great role in this process. The aim of this study is to investigate the ET-1-induced [Ca(2+)]i responses in SPC-A1 cells and to explore its cellular mechanism. [Ca(2+)]i was measured by Fura-2/AM fluorescent assay. Endothelin receptors antagonists, calcium channel blockers and intracellular signal transduction blockers were used to study the underlying mechanism of ET-1-induced [Ca(2+)]i responses in SPC-A1 cells. At the concentration of 1*10(-15) mol/L-1*10(-8) mol/L, ET-1 caused a dose-dependent increase of [Ca(2+)]i in SPC-A1 cells (P <0.05) in vitro . The ET-1-induced (1*10(-10) mol/L) increase of [Ca(2+)]i was blocked by BQ123 at 1*10(-7) mol/L (P <0.05), a highly selective endothelin receptor A (ETAR) antagonist, not by BQ788 at 10(-7) mol/L (P >0.05), a highly selective endothelin receptor B (ETBR) antagonist. Depletion of extracellular Ca(2+) with free Ca(2+) solution and 0.1mmol/L ethyleneglycol bis (2-aminoethyl ether) tetraacetic acid (EGTA) or blockade of voltage dependent calcium channel with nifedipine at 1*10(-6) mol/L significantly reduced the ET-1-induced increase of [Ca(2+)]i. The ET-1-induced (1*10(-10) mol/L) increase of [Ca(2+)]i was also significantly attenuated by U73122 at 1*10(-5) mol/L (P <0.05), a phospholipase C inhibitor, and by Ryanodine at 50*10(-6) mol/L. However, Staurosporine (2*10(-9) mol/L), a protein kinas C inhibitor, exerted no significant effect on the ET-1-induced (1*10(-10) mol/L) increase of [Ca(2+)]i. ET-1 elevates [Ca(2+)]i via activation of ETA receptor. Both phospholipase C/Ca(2+) pathway and Ca(2+) influx through voltage dependent Ca(2+) channel activate by ETAR contribute to this process.