Japanese Thimerosal

‘Effect of thimerosal, a preservative in vaccines, on intracellular Ca(2+)
concentration of rat cerebellar neurons.’

Ueha-Ishibashi T, Oyama Y, Nakao H, Umebayashi C, Nishizaki Y, Tatsuishi
T, Iwase K, Murao K, Seo H. Laboratory of Cellular Signaling, Faculty of Integrated Arts and Sciences, The University of Tokushima, 770-8502, Tokushima, Japan 1: Toxicology. 2004 Jan 15;195(1):77-84.

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
10microM increased the intracellular concentration of Ca(2+) ([Ca(2+)]i)
in a concentration-dependent manner. The potency of 10microM thimerosal to
increase the [Ca(2+)]i was less than that of 10microM 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 10microM thimerosal was
not affected by simultaneous application of 30microM L-cysteine whereas that
of 10microM methylmercury was significantly suppressed.

The potency of thimerosal was similar to that of methylmercury in
the presence of L-cysteine. Both agents at 1microM 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.

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