Mutagenicity testing

Paul Whitehead p.whitehead at dial.pipex.com
Fri May 31 03:43:43 EST 1996

Clearly, assessment of mutagenic (genotoxic) potential of a chemical
in in vitro screens relies on cell uptake of the chemical in question.
Does anybody have any information concerning the effect of particle
size on cell uptake, particularly with regard to chromosomal
aberration assays (CHO or human lymphocytes) and the Ames test?

For example, is there a limit below which particles will be taken up
into the cells even if the test substance is presented as an aqueous
suspension rather than a solution in an organic solvent?  Conversely,
what, if any, is the upper particle size limit whereby such material
will be excluded thus rendering the assays meaningless?

This is a relevant subject since I have the results of several in
vitro assays with negative results where an aqueous suspension was
tested, but positive results when the same (dried) material was
dissolved in eg DMSO.  I am trying to conclude whether this is an
aberration(!) of the test system or that testing of the aqueous
suspensions was meaningless.  Particle size distribution is known for
the materials.

Thanks for any help or pointers to relevant information sources.

Paul Whitehead BSc CBiol MIBiol DABT
United Kingdom
e-mail p.whitehead at dial.pipex.com

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