Environmental and Molecular Mutagenesis - Legacy Tobacco ...

192 1989 EMS Abstracts
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
0
.~
OteS- 'the F~gradual decii3se~n population doubling time observed over the past few years .
(This decrease is likely responsible for the somewhat higher spontaneous mutant
frequencies recent,}y„~ved .) In addition, the use of semi-attached, or other
subculture conditions without trypsinization, contributes to a further reduction in
phenotypic expression time . These data lend further support to the use of AS52 cells
as a more sensitive alternative to the CHO/HPRT assay .
557
FLUORESCENT LIGHT NUTAGENESIS IN SALMONELIJ~T~ ~RINORIUM AND 8SCldERICNIA COLI AS A MODEL
FOR SUNLIGNT-INDUCF.D GENOTOXICITY . L .F . Sta owsnk ki, Jr ., D .B . Say, N .J . Sieszcsad,
W .G . Tuman, K .F . McLaren and D .J . Mecca, Pharmakon Research International, Inc .,
Waverly, PA 18471
During evaluation of a photoactivated therapeutic agent, it was serendipitously
observed that fluorespnt light alone yas quite mutagenio to some tester strains used
in the Salmonella his and E . coli tM reversion assays . The strains were exposed (in
a plate incorporation assay, without petri dish lids) to eight unshielded/unfiltered
40-watt cool white fluorescent bulbs in a laminar flow hood . Treatment 4der thes;
conditions for up to three hours produced time-dependent increases in his and trp
reversion frequencies in strains TA98 and WP2 urA (3- to 6-fold) and strains TA100 and
WP2 uvrA pKM101 (10- to 15-fold), with a plateau generally observed after a 90- to
120-minute exposure . Smaller/variable increases occurred in strains TA1S35 and TA1537,
but none were observed in strains TA1538, TA102 or WP2 . Filtering the light through
polystyrene lids did not completely abolish its mutagenicity observed in strains TA100
and WP2 uvrA pKtt101 under standard plate incorporation conditions (without lids) . The
presence of a photoactivated promutagen in the nutrient/top agars or overnight culture
medium seems remote, since treatment in microtiter wells after washing and resuspension
in phosphate buffer still elicits a mutagenic response . Thus, these cosmion tester
strains may provide the basis for a simple, sensitive, inexpensive model to study
genetic damage induced by natural sunlight, as indicated by the ability of consumer
sunscreens to reduce the mutational response observed under standard plate
incorporation conditions .
MUTAGENESIS BY GLUTATHIONE AND OTHER THIOLS : MECHANISM AND RELEVANCE TO
HEPATOCARCINOGENESIS . A .A . Stark, D .A . Pagano, and E . Zelger. Department of
Biochemistry, Tel-Aviv n vOsTEy, Ramat-Aviv 69978, Tel-Aviv (Israel) ;
Cellular and Genetic Toxicity Branch, N .I .E .H .S ., Research Triangle Park, NC
27709 (USA) .
The mechanism of glutathione (GSH) and other thiols' mutagenesis was
Investigated (Stark at al ., Mut . Res . 177 :45-52, 1987 ; Carcinogenesis
9 :771-777, 1988) . The activation of GSH to a bacterial mutagen 1s catalyzed
by a single enzyme, y-glutamyltranspeptidase (GGT) . GGT cleaves the Yqlutamyl
residue from GSH to form the reactive dipeptide cystetny191yctne
(CG), which is mutagenic 1n the absence of GGT . The mutagenicity of GSH, CG,
and other thiols depends on the pKa of the -SH group and the pH of the
medtum . GSH and CG mutagenesis requires molecular oxygen, is enhanced by
1ron, and Inhibited by lron chelators, radical scavengers, and
H2O2-metabollztng enzymes . Autoxidation of the thiolate anion generates the
(pen)ultimate mutagen H202 . GSH can also drive lipid paroxldatlon in vitro
and tn cultured cells tn the presence of GGT . Elevated GGT levels are often
found in hepatic preneoplastlc foci . The high probability of their
progression to hepatocarcinomas may thus be due to the formation of oxygen
radicals by the GSH-GGT system tn the proximity of these foci .
558
559
DEVELOPMENT OF MONOCLONAL ANTIBODIES RECOGNIZING 4-AMINOBIPHENYL-(SUANOSINE
M . Stefanidis, D . W . Roberts, F . F . Xadlubar and R .M . Santella, National Center for
Toxicological Research, Jefferson, AR (USA) and Columbia University, New York, NY (USA)
Several aromal.ic aminee, including 4-aminobiphenyl, (4-ABP), have been found in
cigarette smoke and are recognized as potent human carcinogens . Exposure to aromatic
animns is believed to be a contributing factor to the increased incidence of bladder
cancer in cigarette smokers . Previously, a polyclonal antibody was developed against
the major 4-ABP--DNA adduct (Cancer Res . 48 :6336,1988) and used to monitor adducts in
lung and bladder epithelial DNA of smokers (IARC publications i89,p .166, 1988) . To
develop monoclonal antibodies to this adduct, BALB/c mice were issiunized with 4-ABPguanosine
coupled to keyhole limpet hemocyanin . The two most sensitive clones, 6D4 end
10114, were characterized as to sensitivity and specificity by competitive enzyme
linked immunoaorbent assay (ELISA) . For both antibodies, 50% inhibitor concentration
is in the range of 1 pmol of adduct . Neither antibody crossreacts with unmodified
50869 3706