Effect of thimerosal, a preservative in vaccines, on intracellular Ca2+ concentration of rat cerebellar neurons.

Abstract The effect of thimerosal, an organomercurial preservative in vaccines, on cerebellar neurons dissociated from 2-week-old rats was compared with those of methylmercury using a flow cytometer with appropriate fluorescent dyes. Thimerosal and methylmercury at concentrations ranging from 0.3 to 10 μM increased the intracellular concentration of Ca 2+ ([Ca 2+ ]i) in a concentration-dependent manner. The potency of 10 μM thimerosal to increase the [Ca 2+ ]i was less than that of 10 μM methylmercury. Their effects on the [Ca 2+ ]i were greatly attenuated, but not completely suppressed, under external Ca 2+ -free condition, suggesting a possibility that both agents increase membrane Ca 2+ permeability and release Ca 2+ from intracellular calcium stores. The effect of 10 μM thimerosal was not affected by simultaneous application of 30 μM l -cysteine whereas that of 10 μM methylmercury was significantly suppressed. The potency of thimerosal was similar to that of methylmercury in the presence of l -cysteine. Both agents at 1 μM or more similarly decreased the cellular content of glutathione in a concentration-dependent manner, suggesting an increase in oxidative stress. Results indicate that thimerosal exerts some cytotoxic actions on cerebellar granule neurons dissociated from 2-week-old rats and its potency is almost similar to that of methylmercury.