Carcinogenesis, Vol 19, 315-320, Copyright © 1998 by Oxford University Press
K Felix, S Lin, GW Bornkamm and S Janz
Small fragments of silicone gels injected intraperitoneally have been used
to induce plasmacytomas in genetically susceptible mice. Silicone oils, in
contrast to silicone gels, are apparently not tumorigenic in the mouse
plasmacytoma system. The reason for this difference as well as the
mechanism of silicone gel-induced plasmacytoma development is poorly
understood. We chose to examine the possibility that low molecular wt
silicone compounds such as siloxanes, leaking from the complex silicone gel
matrix into the surrounding tissue, may be mutagenic. We postulate that
this mutagenicity may be a critical determinant of the plasmacytoma
inducing potency of silicone gels. Six siloxane compounds, either linear or
cyclic di-, tri-, or tetrasiloxanes substituted with methyl or vinyl
moieties, were selected as model compounds to study mutagenicity in
Rat2lambda lacI fibroblasts in vitro. Using phage lambda-derived lacI/lacZ
genes as target/reporter genes to quantitate mutagenesis, and
gamma-cyclodextrin as vehicle to effectively deliver siloxanes, we found
that exposure to 50 microM of tetravinyl-tetramethylcyclo-tetrasiloxane
(tetravinyl D4) resulted in a modest 1.7-fold increase of mutant
frequencies over controls in Rat2lambda lacI cells. In related toxicity
experiments, tetravinyl D4 was shown to perturb lipid membranes leading to
a loss of cytosolic glutathione (GSH), which by itself resulted in a
1.5-fold increased mutant rate in Rat2lambda lacI cells. We conclude that
certain siloxanes may act as direct mutagens in mammalian cells. In
addition, siloxane-induced mutagenicity may be enhanced by the depletion of
intracellular GSH caused by the interaction of lipophilic siloxanes with
cell membranes.
ARTICLES
Tetravinyl-tetramethylcyclo-tetrasiloxane (tetravinyl D4) is a mutagen in Rat2lambda lacI fibroblasts
Laboratory of Genetics, DBS, NCI, NIH, Bethesda, MD 20892, USA. felixk@dc37a.nci.nih.gov
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K. Kulig and K. Felix Re: Felix,K., Lin,S., Bornkamm,G.W. and Janz,S. (1998) Tetravinyl-tetramethylcyclo-tetrasiloxane (tetravinyl D4) is a mutagen in Rat2{lambda}lacI fibroblasts. Carcinogenesis, 19, 315–320 Carcinogenesis, August 1, 1999; 20(8): 1653 - 1654. [Full Text] [PDF] |
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