Comparison of the Effects of Trimethyltin on the Intracellular Calcium Levels in Spiral Ganglion Cells and Outer Hair Cells

Abstract

Cochlear impairment by trimethyltin chloride (TMT), a potential contaminant of marine paints and polyvinyl chloride tubing, has been well demonstrated. Its toxic effect on the inner hair cells (IHC)-spiral ganglion cell (SGC) unit occurs almost immediately while disruption of outer hair cell (OHC) function does not occur unitl several hours after exposure. in this experiment, OHCs and SGCs from pigmented guinea pigs were tested in vitro to determine the role of enhanced intracellular calcium [Ca²⁺]i levels in TMT ototoxicity and to determine the sources of enhanced [Ca²⁺]i. the latter was determined by experiments using artificial perilymph without Ca ⁺ and by use of the Ca ⁺ channel blocker, nifedipine. the data show that TMT elevates [Ca²⁺]i in both OHC and SGC. the elevation of [Ca²⁺]i in SGC is much more rapid and larger than that in OHC. the elevation of [Ca²⁺]i in SGC can be attenuated by removing Ca²⁺ from artificial perilymph or pretreating with nifedipine, but neither of these treatments is effective in OHC. the results suggest that TMT disrupts intracellular storage of Ca²⁺ in OHCs and SGCs, but that is also enhancing influx of Ca²⁺ from extracellular sources in the SGCs.

Key Words:

• ototoxicity
• spiral ganglion cells
• outer hair cells
• trimethyltin
• intracellular calcium