Ca2+ Depletion Facilitates Taurine Release in Cultured Rat Astrocytes

Removal of external Ca2+ facilitated endogenous taurine release in cultured rat astrocytes. The stimulated release was not affected by furosemide, sucrose, tetrodotoxin and 3,4-dichlorobenzamil, but partially inhibited by nifedipine. Omission of external Na+ increased basal taurine release, and the effects of Na+ removal and Ca2+ depletion on the release were additive. The Na(+)-free condition did not affect Ca2+ paradox-induced cell death in astrocytes. These findings suggest that Ca2+ depletion facilitates taurine release in a mechanism independent of volume and the Na+ gradient and that the release is not involved in Ca2+ paradox-induced delayed cell toxicity in astrocytes.