Environmental and Molecular Mutagenesis - Legacy Tobacco ...

102 1989 EMS Abstracts
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
Notes to assess the importance of toxicity and variations to protocol . 3 of the chemicals
were also tested in similar protocol variations (except 3-21 inatead of 6-18) in human
lymphocytes (HL) . The fourth, maleic anhydride, became positive in a 6-18 protocol
+ S-9 . Sodium dehydroacetate became positive at higher dosea in CHL cells after 24 hours
-S-9 . In HL it was only positive after 24 hours -3-9, when doses giving > 50% toxicity
could be found . Cocaine hydrochloride became positive in all 4 phases in CML cells .
In HL it required doses > 10 mM to get similar positive results . 6-mercaptopurine
became positive - and . S-9 in 6-18 protocols in CHL cells on a second retest when some
doses giving > 50% toxicity were used . In ML, it was such swre positive over 48 hours
-S-9 than 24 hours but was negative at much higher doses in 3-21 protocols . The results
show that (i) "difficult" clastogens can be detected in HL as well as CHL cells ; (ii)
prolonged treatments are not always necessary if ad .quate toxicity (>50%) is achieved ;
(iii) higher doses are generally needed in pulse treatment/recovery protocols, and may
not achieve adequate toxicity even at doses > 10mM .
292
X-RAY MUTAGENESIS OF A GPT TARGET IN CHINESE HAMSTER V79 CELLS YIELDS SMALL COLONY
MUTANTS . C .S . Klein and T .G . Rossman (Presented by E .T . Snow) . Institute of Evironmental
Medicine, NYU Medical Center, P .O .Box 817, Tuxedo, NY 10987 (USA) .
The E . coli ct gene encoding xanthine-guanine phosphoribosyl transferase has
been stably transfected into HPRT' Chinese hamster V79 cells . One cell line (g12)
maintains a low spontaneous mutation frequency (2 x 10-5), and is useful for comparative
mutagenesis studies (ykt vs . hprt) . Alkylating agents such as N-methyl-N'nitro-N-nitrosoguanidine
(MNNG) and P-propiolactone (BPL) are equally mutagenic to
the ypt and hprt loci at doses (MNNG, 0-2 )ig/ml ; BPL, 0-2 mM) which yield greater
than 50% survival of the cells . UV (0-8 J/M2) is 3-4 times more mutagenic at 2pt
than hprt in V79 cells at relatively non-toxic doses . The y~t locus of g12 transfectants
also appears to be more (3-4x) sensitive than the endogenous hprt to x-ray
(0-750 rads) induced mutations . This data is in agreement with previously reported
x-ray mutagenesis in gpt+ CHO (Stankowski and Hsie, 1986, Radiat . Res . 105 :37) . An
abundance of small qpt mutant colonies were found in g12 cells at high x-ray doses
which are not seen in gpt mutants of CHO . Small colony mutants in mouse lymphoma
cells are believed to arise from cells which have sustained chromosomal and deletion
mutations at the tk locus . Deletions, especially multilocus deletions, are difficult
to study in most mammalian assays since they are generally lethal events . The data
suggest that 912 cells may be useful for studying clastogen-induced mutagenesis .
Further studies are underway to define the mechanisms of small colony formation in
these cells .
293
S9UDIES ON '1HE II-ID(1f.TICN OF CY10Qt4ZE P450 LSO@Pl)R['S BY 2-AMIPD-1 (4 .5bJP1QtIDI)4E
(phIp) Alm 2-MQP43 .8-0D6DOQ.IIOAllip(4,5-f)%RNID(ALIM (MeIQc) IN VARIOUS OHfM RY!(
MME RAIS .
M. Kleman, E. (iservik . P. LinderJ:os ard J .-A. Qstafasoo. DepartmaK of Medical Nutriticn, Raxolinmka
Institute, Stockhulm, SYweden .
7he mrtasenic ard caninaserdc hetemcyclic amires fonaed in proteinrich food upan eookin6 are
all deperdent an metabolic activation for the formation of their ultismtely active fonre . It was
shown by previom imestisators, that rat cytoduvne P450 forms C . d ard the canstitutive P450 msle
in vitiv performs this activation. fie aubJect of the present imestibatien 4ms to stt* if the
food proMutasens phlP and MeIQc have the ability to irduce cytochrome P450 isoe :aymes and thus to
ird:re their an activation . 'Rmee dnses of 50 uR MeIQc or phlP per kb b .w . were siven to sale
Wistar rats on three consecutive days . Betairphtoflawne (BNF) aas given aa a positive eontrol at
40 ms per lg b.w . and 0 .9% NaCI as negative control . On the fonrth day all ani :rels were sacrificed
by decapitation ard lurg, forestomach, stomach, smsll intestine, liver ard kidney aere talmt .
MicYosrnrs vrre prepared fiam all orsems ard inmdiately froaen at -70'C . 9000 & sapernatant (S-9)
was also prepared from the livers . 1fie microsants were used In liestern inmrnblots a6aiist antibodies
raised in rabbit to cytochYam P450,,,o srd cytorlaarc i450PR. A positive response uss
obtained with liver microsares frao the MeIt* treated ardxsls a6ainst the anti
Measurn~ents of EUrncy~on :fin4deetlrylase activity cordinped the irductiVe effect o Me•
cytoch- KS%s in liver and sh4wed a sigdflcantly increased activity of these cytoc]:roee PW
forms also in the iddneys of the MeIQc irduced rats . 7he liver S-9 aanples were used in hms test
an strain TA98 a6ainst MelW and Aflatodn BI . Slaprisirgly. the phlp induced livers ah4wed a
significantly increased capecity to activate MeIQc, ahile the MeIQc liver S 9 :s were fnt different
fiom the controls .
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