Effect of endothelin-1 on cytosolic calcium ions in cultured human endothelial cells

The effects of endothelin-1 on cytosolic Ca2and inositol 1,4,5-triphosphate (IP3) levels were investigated in cultured, untreated human endothelial cells and in endothelial cells pretreated with anti-endothelin-1 serum for 24 h to exclude the effect of endogenous endothelin-1. Endothelin-1 was found to increase the intracellular Ca2level, either in the presence or absence of extracellular Ca2, in endothelial cells pretreated with antiserum by the fura-2 fluorescence technique. IP3levels immediately started to rise following endothelin-1 stimulation. Resting intracellular Ca2levels were significantly lower when the cells were pretreated with antiserum than without antiserum pretreatment. Following stimulation by endothelin-1, intracellular Ca2and IP3levels in endothelial cells pretreated with antiserum increased significantly compared to those in untreated endothelial cells. Endothelin-1 also increased 45Ca influx from the extracellular space. These results suggest that endothelin-1 increases intracellular Ca2in endothelial cells through extracellular Ca2-dependent mechanisms and by the release of Ca2from intracellular stores, this presumably being induced by IP3formation.