Change of cytosolic Ca2+ mobility in cultured bovine corneal endothelial cells by endothelin-1

The effect of endothelin-1 (ET-1) on the intracellular free Ca2+ ([Ca2+](i)) in cultured bovine corneal endothelial cells was studied after loading with fura-2-AM. In Ca2+-containing buffer and Ca2+-free buffer, ET-1 induced a significant rise in [Ca2+](i) at concentrations from 10(-9) to 10(-7) M. In Cal(2+)free buffer, pretreatment of the cells with ET-1 inhibited thapsigargin-induced [Ca2+]i increase and carbonylcyanide m-chlorophenylhydrazone (CCCP)-induced Ca2+ release by 99% and 62%, respectively. Pretreatment of the cells with thapsigargin or CCCP also inhibited ET-I -induced [Ca2+]i rise by 36% and 92%, respectively. In Ca2+-containing buffer, the ETA receptor antagonist (BQ123) and ETB receptor antagonist (BQ788) partially inhibited ET-1-induced [Ca2+], by 92% and 98%, respectively. Nifedipine and La3+ also inhibited ET-1-induced [Ca2+, increase by 26% and 91%, respectively. The intracellular calcium release caused by ET-1 was partially inhibited by phospholipase C inhibitor (U73122). After incubation of the cells with ET-1 in Ca2+-free buffer, the addition of 5 mM CaCl2 increased Ca2+ influx, implying that release of Ca2+ from internal stores caused by ET-I further induced capacitative Ca2+ entry. These data suggest that ET-1-induced [Ca2+](i) rise in bovine corneal endothelial cells are mediated by ETA receptor, ETB receptor, La3+-sensitive Ca2+ pump and L-type voltage-operated Ca2+ channel, leading to Ca2+ influx. ET-1 also increased the internal Ca2+ release from endoplasmic reticulum and mitochondria Ca2+ stores followed by capacitative Ca2+ entry. ET-1-induced intracellular Ca2+ release was modulated by phospholipase C-coupled events.