Environmental and Molecular Mutagenesis - Legacy Tobacco ...

312
ANTIMUTAGENIC EFFECTS OF GLUTATHIONE-S-TRANSFERASE INDUCTION IN E . COLI .
S . Kuo and D .M . Shankel, Department of Microbiology, The University of Kansas,
Lawrence, Kansas 66045 .
The glutathione-S-transferases are dimeric enzymes which mediate the detoxification
of potentially mutagenic electrophiles via conjugation to the tripeptide
y-glutamyl cysteinyl glycine (glutathione) . Glutathione-S-transferases are also
present in a variety of bacteria . Using the E . coli K12ND160 system, it was observed
that pretreatment of E . coli with butylated hydroxy anisole (BHA) results in a
decrease in the frequency of induced revertants caused by ethylmethanesulfonate,
nitrofurazone, quinacrine and hydrogen peroxide . This reduction in induced mutants
occurred concomitant with an increase in activity of glutathione-S-transferase in
the organism . Thus this enzyme may play an important role in the protective arsenal
of E . coli against potentially genotoxic agents . The significance of these results
and related findings will be discussed as they relate to the mechanism of antimutagenesis
.
313
BIOLOGICAL SIGNIFICANCE OF INDUCED ENDOREDUPLICATION . A . Lafi and J . M . Parry, School
of Biological Sciences, University College of Swansea, Singleton Park, Swansea SA2 8PP .
Several authors have demonstrated that exposure of cultured cells to a number of
chemical agents results to an increase in endoreduplication . Here we present
comparative data on the ability of tobacco particulate matter (TPM), derived from
three cigarette types, to induce endoreduplication . A dose related increase was
observed but there were no consistently significant differences related to the tar/
nicotine levels per cigarette used . In cells allowed to recover from TPM treatment
there was an increase in polyploidy and a decrease in endoreduplication suggesting
that the increase in polyploidy observed was at least partly due to the recovery of
cells from endoreduplication . Chromosome aberrations were induced in all three types
of cells (diploids, endoreduplicated and polyploids) . However, the levels of all
types of aberrations were higher in the endoreduplicating cells when compared to
diploids and polyploids . This was a very unexpected resuit since it has previously
been shown that endoreduplicating cells (when compared to diploid and ordinary
tetraploid metaphases) are seen to contain a decreased frequency of SCEs (Speit . G .,
Vogel, W . and Mehnert, K . 1985, Chromosoma, 89, 79-84) ; The presence of cells with
different ploidy levels may have a significant effect upon the capacity of some
chromosome abnormalities to be transmitted to progeny cultures .
314
IN VTW G[fEPIC =C1TY FFOIUCfl[S FYR TfQ3tAP1 ;iRTC HOOlW PCFMAAITQIS. Robert S . Lake, Safety
Evaluation Center, Schering Corporation, Lafayette, NJ 07848 .
Therapeutic proteins (cytokinas, gtvvth factors and imniwnndulatory polypeptides) pose tw special
problem for routine in vitro safety testirg . (1) Mode of action is usuall,y species and cell-type
specific such that the protein itself is rot acutely toxic and (2) clinically used dng fomailation
excipients can modify test system regpor~ses . Dng substanoe is usuall;y ptrsented for testing as
lyophilized active in for+iulatio ;tis as siaple as saline or as oanplex as mixtures with buffers, bulking
agents, stabilizers, antioxidents, ard wettitg ageits . Ideally, the first ptoblem can be dealt with by
the use of primate tissues or oetl types laaun to retain appropriate receptors . For qualiq+ control
pucposes, sub4 .msn system (such as the Mrs Test) are atill weful for detectirg potential activity of
excipients, contaminants, or biottac.tfonmatien-degtadation products . The seoatd problem neoassitates
exteruive pilot trials to establish tolerated dose wlueas of fotsilatien vithout the active protein
(placebo control solution or control vehicle) and subsequently cantrolling for toequal vehicle effects in
all dose ard control groups. This latter approach involves adjusting all treataent carditiom to the
level (v/v) of vehicle control solution used in the high-dose gtroup . If the vehicle is t .duly toxic to
backgroud endpoints or interferes with positive control respas es, thet the foraulated therapeutic
protein canot be tested . In effect, since the active protein is nort-tcodc, the ssscian tolerated dose
level is set or deterndned by the level of vehicle control solution tolerated by negstive aod/or positive
control groups . Failure to andify study desigrts can lesd to false negatives if the formulation
conpone.nts suppress S9 sietabolisn or expcesaion of sutation . False positives could ocas- if spontaneam
(backgrand) levels are erimoed or cytotcedcities from other systea emipaknts are eliminated . Such
forau]ation effects have been observed in bacterial wtasgenaais, huaan l,ysptwcyte qtagenetics, CfA-tCPRP
and rat hepqtocyte UDS studies .
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
1989 EMS Abstracts 109
Notes