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

The effects of endothelin-1 on cytosolic Ca2+ and 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 Ca2+ level, either in the presence or absence of extracellular Ca2+, in endothelial cells pretreated with antiserum by the fura-2 fluorescence technique. IP3 levels immediately started to rise following endothelin-1 stimulation. Resting intracellular Ca2+ levels were significantly lower when the cells were pretreated with antiserum than without antiserum pretreatment. Following stimulation by endothelin-1, intracellular Ca2+ and IP3 levels 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 Ca2+ in endothelial cells through extracellular Ca2(+)-dependent mechanisms and by the release of Ca2+ from intracellular stores, this presumably being induced by IP3 formation.