The effect of sphingosine on intracullular calcium signalling in glioma C6 cells was studied with Fura-2 video imaging technique.Sphingosine had a direct effect on changes in cytosolic Ca2+ concentration only when applied at high concentation of 100 muM, causing the cytosolic Ca2+ level to rise.However, at a much lower concentration of 15 muM sphingosine diminished calcium responses triggered by thapsigargin and ionomycin (calcium ionophore).Since responses to thapsigargin and ionomycin were blocked in Ca2+ -free medium, we postulate that sphingosine is acting on the intracellular calcium stores.Additionally, sphingosine (at 15muM and 100muM)markedly decreases thapsigargin-induced sustained elevation in cytosolic Ca2+ concentation, indicating its inhibitory effect in thapsigargin-evoked Ca2+ influx.Sphingosine is known inhibitor of protein kinase C and the involvment of this enzyme is postulated in the modulatory effects of spingosine on intracellular calcium dynamics.
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