Kwack, SJ; Rhee, GS; Kim, SS; Sohn, KH; Kim, SH; Chae, SY; Choi, YW; Won, YH; Park, KL
The purpose of our study was to evaluate the toxicity of the thimerosal in embryos and neonates. Thimerosal (also known as mercurothiolate) is a mercury-containing compound used in trace amounts to prevent bacteria and other organisms from contaminating vaccines, especially in 'opened multi-dose vials. The toxicity of mercury is well known and those most at risk occurs in unborn babies and newborn babies. Test methods included in vitro whole embryo culture (WEC) system and in vivo test of neonatal toxicity in Wistar rats. Ethylmercury and methylmercury were used as positive controls for the evaluating of toxic effects of mercury. In WEC assay, treated concentrations of thimerosal, ethylmercury and methylmercury were up to 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5 and 5 ug/ml, respectively. All compounds didn't show any morphological abnormalities, but showed retardation of growth and development in dose dependent manner (>0.5 ug/ml). These data indicated that thimerosal showed developmental toxicity in vitro. In vivo neonatal toxicity, Wistar rats were administered subcutaneously with thimerosal, ethylmercury, or methylmercury (5, 25, 50, 250, and 500 ug/kg) during from postnatal day (PND) 4 to 25. Significant effects of these compounds on relative organ weights and organ morphology were not observed in this experiment. However, accumulation of mercury was detected in the kidney and testis when treated with thimerosal, ethyl mercury, or methylmercury. These results suggest that thimerosal may be a harmful compound to embryo and neonate, but used concentration of thimerosal in these experiments is much higher than that of clinical application. Further investigation is needed on the safety of vaccine components, i.e. a thimerosal using in vitro and in vivo tests in the future.