EN
Thimerosal (TH), an ethylmercury complex of thiosalicylic acid has been used as preservative in vaccines. Inspired by a known high affi nity of mercury for thiol groups, we examined whether the presence of L-cysteine (Cys), D,L-homocysteine (Hcy), Nacetyl cysteine (NAC), L-methionine (Met) and glutathione (GSH) in extracellular space could infl uence the viability, intracellular calcium concentration ([Ca2+]i ) and mitochondrial membrane potential in rat cerebellar granule cells. The cells were exposed to 500 nM TH for 48 h or 15 μM TH for 10 min. The loss of cells viability could be prevented partially or wholly, in a dose-dependent manner, by 60, 120 or 600 μM Cys, Hcy, NAC and GSH, but not by Met. The elevation in [Ca2+]i and mitochondrial potential induced by 25 μM TH were abolished by all compounds studied, except for Met, at 600 μM. The loss of the ethylmercury moiety from TH as a result of interaction with thiols studied was monitored by 1 Hand 199Hg-NMR spectroscopy. This extracelullar process may be responsible for the neuroprotection seen in cerebellar cell culture, but also provides a molecular pathway for redistribution of TH derived toxic ethylmercury in the organism.