[Thiol reagent thimerosal-induced Ca2+ mobilization in isolated guinea pig cochlear outer hair cells].
Zhonghua Er Bi Yan Hou Ke Za Zhi. 2000 Jun ;35(3):192-5. PMID: 12768775
OBJECTIVE: To understand mechanism of cochlear outer hair cells (OHCs) intracellular Ca2+ mobilization further.
METHODS: Intracellular calcium of isolated guinea pig was investigated using thimerosal, a--SH group oxidizing agent, and fura-2 fluorescence ratio imaging microscopy.
RESULTS: In the presence of thimerosal, intracellular Ca2+ concentrations ([Ca2+]i) of OHCs were elevated in a dose-dependent manner. Even in Ca(2+)-free medium, Ca2+ response was still induced. The effects of thimerosal on [Ca2+]i were completely blocked and reversed by (DTT). Neither 1-100 mumol/L ryanodine nor 5-20 mmol/L caffeine altered the effects of thimerosal. Pretreatment with pertussis toxin (PTX) for 30 min did not affect the thimerosal-induced increase in [Ca2+]i The increase in [Ca2+]i when Ca2+ was added during thimerosal application in Ca(2+)-free medium was almost completely blocked by 500 mol/L LaCl3, while nifedipine did not inhibit further increase in [Ca2+]i caused by thimerosal.
CONCLUSION: Oxidation of the -SH group of the OHC membrane can induce a Ca2+ release from intracellular Ca2+ stores, which are ryanodine- and caffeine-insensitive, and Ca2+ influx through non-specific Ca2+ channels, but not the nifedipine-sensitive Ca2+ Channels. The possible oxidation of--SH group gated Ca2+ channels in OHCs are worthy of further study.