Potentiation by Ca2+ ionophores and inhibition by extracellular KCl of endothelin-induced phosphoinositide turnover in C6 glioma cells
Journal
Neurochemistry International
Journal Volume
21
Journal Issue
2
Pages
293-301
Date Issued
1992
Author(s)
Chuang D.-M.
Abstract
Interactions between endothelin-1 (ET)-induced phosphoinositide (PI) hydrolysis and agents that increase Ca2+ influx (i.e. A23187 and ionomycin) or induce depolarization (i.e. KCl) were investigated using C6 glioma. A23187 dose-dependently potentiated ET (30 nM)- and ATP (100 μM)-induced [3H]inositol phosphate (IP) accumulation. This potentiation was associated with an increase in the maximal stimulation elicited by both ET and ATP but their EC50 values were unchanged. This effect of A23187 occurred at concentrations that did not affect basal PI turnover; i.e. 10 nM-3 μM. Ionomycin within the range of 1 nM- 1μM also significantly enhanced ET-induced PI breakdown and this effect was associated with an increase of [Ca2+]i, KCl in a concentration-dependent manner (14.7-54.7 mM) markedly inhibited PI breakdown elicited by ET and ATP, but had much less inhibition on basal activity and no effect on A23187- and ionomycin-induced responses. In parallel, KCl added before or after ET, sharply attenuated the increase of ET-induced [Ca2+]i but did not affect basal level or ionomycin-induced [Ca2+]i response. Neither the potentiation by A23187 nor the inhibition by KCl of ET-induced PI turnover was observed in cultured cerebellar astrocytes. Our results suggest that the cell type-specific regulation by Ca2+ ionophores and KCl on ET-induced PI metabolism is closely related to perturbation of [Ca2+]i. © 1992.
SDGs
Type
journal article