Taurine modulates calcium influx through L-type voltage-gated calcium channels in isolated cochlear outer hair cells in guinea pigs

Taurine has been proposed to play a role in calcium modulation. To explore the effect of taurine on intracellular calcium homeostasis of isolated cochlear outer hair cells and on the gentamycin-induced inhibition of calcium influx evoked by high K+ depolarization, we employed fluo-3 imaging of intracellular calcium ([Ca2+]i) via confocal laser scanning microscopy to measure real-time changes of [Ca2+]i. We found that the sole application of taurine (5, 10, 20 mM) induced a transient [Ca2+]i increase in a concentration-dependent manner, which was inhibited either by the application of an L-type calcium-channel blocker nifedipine or a calcium-free medium. Pre-incubation with 1 mM gentamicin induced inhibition of [Ca2+]i elevation evoked by high K+. Short-term (10 min) exposure with a high level of taurine (20 mM) prevented this inhibition. These results indicated that taurine at a high concentration was able to promote calcium influx through L-type calcium channels in isolated outer hair cells and antagonize gentamycin-induced inhibition of calcium elevation evoked by high K+ by its calcium homeostatic effect.