Environmental and Molecular Mutagenesis - Legacy Tobacco ...

519
XRS-5 CELLS ARE NOT 47PERSENSITIVE TO X-RAY-INDUCED MUTATION .
J . D . Shadley, M . Toohill, J . Whitlock, J . Rotmensch and J . L .
Schwartz, University-qpf Chicago Medical Center, Chicago, IL (USA)
The Chinese hamster ovary (CHO) cell line xrs-5 has been shown
to be hypersensitive to the cytotoxic effects of X-rays compared
to the parental line K1 . In agreement with previous reports on
this cell line, we find that xrs-5 cells are : 1) 3 fold more
sensitive to the cytotoxic effects of X-rays (D10) than K1) 2)
rejoin only 60% of their gamma-ray-induced double strand breaks
compared to over 90% for Kl ; and 3) 7 fold more sensitive to Xray-induced
G2 chromatid-aberratiotTS than Kl . Given its
hypersensitivity to the above endpoints, we tested to see if xrs-
5 cells are also hypersensistive to X-ray-induced HGPRT mutation
compared to K1 . Xrs-5 cells gave similar 6-thioguanine resistant
induced mutation frequencies per Gy dose (1 .9 x 10-5 for xrs-5
vs 1 .8 x 10-5 for Kl) . When based on equal survival levels,
either DO or D10, X-rays induce only one-half to one-third
the frequency of 6-TG resistance in xrs-5 compared to K1 . Thus,
xrs-5 cells are as mutable if not less mutable than K1 cells . If
the deficiency in double-strand break rejoining is in part
responsible for the hypersensitivity to X-ray-induced cytoxicity
and chromosomal aberrations, then it does not appear to affect
mutation induction . Research supported by Department of Energy
DE-FG02-88ER60661 .
520
ExxAMCED ASSAYS DETECT INCREASED CNROMOSOME DAMAGE ARD SIST[R CNR0N0S0ME ExCNANG[S IN
xER01N ADDICIS . D .A .Shaf .r, V .G .tlunbar, A .Falek, R .N .Don .hoe, J .J .Maddan . E~ery Univ .
and GeorRis Mental Xeatth Inst ., Atlanta, GA 30306
To refine previous studies of chromosome damage (CD) and sister chromatid exchanSes
(SCE) in heroin addicts, we applled eethods re developed to enhance detection of the
cytopenetic effects of lor-l w .l radlation expesure in hospital rerkers . For CD
analysis, our TFC• .nhanced proeedure oonslsted of traatment at setup with 1x10•7N FdU
and Lx10-SM dT to Inhibit thymidytate synthetase and to satisfy that induced
require .ent, and treat .ent in G with oaffein . (2 .2 ∎M) to inhibit repair syfthesis .
For SCE enhaneewent, only caffel ne was used but traat~ant ras extandod traek thru S
phase (19 hrs before harvest) . UsinO s atandard and an enhaneed CD and fCE eulture per
subject, blood samples rera evaluated from 20 street heroin addicts and 22 controls .
Standard 2-day CD and 3-day SC[ assays showed insiGnificant sonotoxic Increases in
addicts vhile the enhanced CD and SCE assays showed highly significant Increases . Most
CD events were in the for∎ of ehromatid and ehromososa iruka . There rere no rings and
a fev dicentrics Yare only observed in the TiC-enhanead eultures . AltheuGA
quadrlradlals are usually rare, 10 vere found In addict TFC•cultures and 3 In control
TFC-cultures . V(th the standard CD assay, the level of chromosome breaks per 100 e .lls
~as .727 for controls and 1 .OS6 for addicts (not siGntf .) . Yith the TFC-enhancad assay,
the same e usure shored t .i63 chrosose .e bruks for eentrols and 5 .163 fer .ddlet .
(highly signif . p< .0001) . A hiGhly siGnifiaant dtfferenca ras also observed for
chroeatid dasa9e with the TFC-anhancad assay although such damage ts not typloally
considered indicatlve of J„a vlvo chro .oso .e daea0e (chro .atid breaks per 100 callst
16 .793 for eontrols ; 4 l .191 for addicta) . The SCE data Gave sio ilar si0nif/eant
differences . standard SCE cultures showed 10 .892 SCE/cell for eontrola and 11 .732
SCE/cell for addicts . Vith CAF enhanca .ent thare rara 13 .0! SC[/oell for controls and
17 .05 SCE/cell for addiets (p< .006) . Tha abeve flndlnGa lnd/eats that tAe deteetlen Of
ICEWICD and SCE affeces can be siGnifleantly anAane .d by the use of tAass nar pree .durss .
The findinG of increased chromatid damage also auGGU ts a ner interpretation of CO
effects since chro .atld effects •ust have occurred poat S•phase . Perhaps exposure to
cheoicals, druGS and environ .ental agents ∎ay not only leave a residue of DNA and/or
chromosome damage but also an indueed sensitivity to further Genotoxic damage .
521
ACTIVITY OF DINITROPYRENES IN THE INTRASANGUINOUS HOST MEDIATED ASSAY .
A .B .Shah, I .R .Rowland and R .D .Combes, School of Biological Sciences,
Portsmouth Polytechnic, U .K ., B .I .B .R .A ., U .K ., and I .R .I . Ltd ., U .K .
Dinitropyrenes, present in polluted air, are potent direct-acting
mutagens in Salmonella tvnhimurium TA 98 . This mutagenicity is markedly
reduced in the presence of mammalian hepatic S9 or microsomes . Since
most in vitro test systems do not adequately simulate conditions
encountered in the intact animal, we have investigated dinitropyrene
mutagenicity to Salmonella in the host mediated assay . 1,8-
Dinitropyrene (1,8-DNP) given 2.2. to BALB/c mice induced a weak
mutagenic effect in S . typhimurium TA 98 recovered from the liver 1
hour after J,y . administration ; over the entire dose range tested no
toxicity to bacterial cells was detected . Mutation induction in vivo
was dose related with maximum response (71t9 revertants/plate) at lmg
DNP/kg body weight. This optimum dose however, was non-mutagenic to
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
1989 EMS Abstracts 179
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