Differential effects of raising and lowering intracellular glutathione levels on the cytotoxicity of allyl isothiocyanate, tert-butylhydroperoxide and chlorodinitrobenzene.
The influence of intracellular glutathione (GSH) on cytotoxicity was studied in vitro by altering the intracellular GSH level of Chang liver cells. Lowering the GSH level was achieved by treating cells with diethyl maleate (155 mum), while the intracellular GSH level was raised by cellular incubation with the monoethyl ester of glutathione (20 mm). The cytoxicity of three compounds that are known to react differently with GSH was tested using the cloning efficiency assay. Allyl isothiocyanate reacts reversibly with GSH and in previous work it was shown that the toxicity of the GSH conjugate was due to the release of the free isothiocyanate. In this study we found that changing the intracellular GSH level had no influence on the cytotoxicity of this compound. This points to the cell membrane as the primary target, although the possibility of GSH being involved as a transporting agent cannot be completely excluded. Chlorodinitrobenzene conjugates easily with GSH, and in bacterial assays it was found that depletion of intracellular GSH enhanced the mutagenic effect. After raising the intracellular GSH level in Chang cells this compound was found to be more toxic, and after lowering the GSH level less toxicity was found, indicating a role for GSH in the activation of chlorodinitrobenzene. For comparison tert-butylhydroperoxide was chosen, because it is known to be detoxified by GSH. Lowering the intracellular GSH level did indeed result in higher cytotoxicity, but after elevating the GSH level no increase in cloning efficiency was observed, indicating that there are more factors involved in tert-butylhydroperoxide cytotoxicity.
Bruggeman
I M
IM
Department of Toxicology, Agricultural University, De Dreijen 12, 6703 BC Wageningen, The Netherlands.
Spenkelink
A
A
Temmink
J H
JH
van Bladeren
P J
PJ