Environmental and Molecular Mutagenesis - Legacy Tobacco ...

dose rate of 6 .9 Gy/min either at early or late GI, followed of a round of division in
presence of bromodeoxyuridine (BrdU) dose of 0 .5 mg/gm bd wt . There was a significant
decrease in SCE frequency at early Gj with respect to those irradiated at late G1 . The
se data suggest that BrdU substituted cells are able to repair about fifty percent of
the lesions induced by gamma radiation during G1 . Also the adequeate BrdU dose to obtain
a clear differentiation of sister chromatids and the capacity of ga- a radiation
to induce SCEs in salivary gland cells were determined . The BrdU dose which permits a
good differentiation of sister chromatids (0 .3 mg/g bd wt) was one third of that required
in bone marrow cells . The gaama radiation induced a significant increase of --
SCEs with a similar efficiency to that obtained in bone marrow .
Acknowledgments : We wish to thank Jorge Mercader N ., Angel Reyes P ., Perfecto Aguilar
V ., Felipe Beltran B . and Enrique FernEndez V., for their excellent technical assistance
.
383
RESTRICI7ON ENZYMES AND CYTOGENETIC DAMAGE . W.F. Morgan, H .W. Chung. J .W. Phillips and RA
Winegar, Laboratory of Radiobiology and Environmental Health, University of California, San Fraacisco, CA (USA)
Bacterial restriction endonucleases recognize specific, rather short sequences of DNA as binding sites and produce
either blunt-ended or cohesive-ended DNA double-strand breaks . Eleetroporatioe Is a rapid and extremely efficient
method for pcrmeabilning Chinese hamster ovary (CHO) cells, permitting the introduction of restrictioa enzymes into
exponentially growing cells. We have used restriction enzymes with different recognition sequences and different
cutting frequencies to generate double-strand breaks in CHO cells and have examined the role of these breaks in
cytogenetic damage. Restriction enzymes electroporated into cells readily induced chromosome aberratioos at all
stages of the cell cycle. Enzymes generating blunt-ended DNA double-strand breaks induced more chromosome
damage compared with enzymes generating coheaive-ended breaks . When restriction enzymes were eledroporated
into exponentially growing cells during the second replication cycle in bromodeoxyuridise, and sister chromatid
exchanges (SCEs) analyzed at the subsequent mitosis, we found no inaease in SCE frequency . Many enzymes
induced aberrant metaphase chromosomes, but SCE frequency was not increased in those cells. These results indicate
that in our hands, restriction enzyme-induced DNA double-strand breaks give rise to chromosome abenaNons, but do
not lead to SCE formation . Work supported by the Office of Health and Environmental Research of the US . Dept . of
Energy under contract DE-AC03-76-SF01012 .
384 .
GENOTOXICITY IN RODENT HEPATOCYTES AND CARCINOGENICITY OF ANTHRAQUINONES .
H . Mori, N . Yoshimi, S . Sugie, H . Iwata, T . Tanaka, and K . Kawai, Gifu University School
of Medicine, Gifu (Japan), and Chukyo Women's University, Ohbu, Aichi (Japan)
A large number of anthraquinones and their derivatives have been isolated from higher
plants and fungi, and some of them have been widely used as colorants in food, cosmetics,
hair dyes and textiles . Luteoskyrin and rugulosin isolated from Penicillium islandicum
are known as hepatocarcinogenic anthraquinoids . Emodin from the samerun-gus
has been shown to be mutagenic in bacterial mutagenicity assay . We have demonstrated
genotoxicity of some anthraquinones such as 1,8-dihydroxyanthraquinone (chrysazin)
which has been used as a popular laxative, in the hepatocyte/DNA repair assay . In the
genotoxicity assay, 1,2-, 1,4-, and 1,5-dihydroxyanthraquinones were negative, although
1-hydroxyanthraquinone and 1,8-dihydroxyanthraquinone generated clearly positive res-
ponse of DNA repair, suggesting a mutual relationship between the genotoxicity and structures
of anthraquinones . Carcinogenicity testing of chryeazin was done using rats
and mice . In rats, chrysazin was tumorigenic to cecum and colon . In mice, the chemical
showed carcinogenic potentials in the large bowel and liver . Carcinogenicity of 1-hydroxyanthraquinone
was also examined in rats . Carcinogenicity of this naturally occurring
anthraquinone was manifested in cecum, colon and liver . The carcinogenic effect of
1-hydroxyanthraquinone appeared to be stronger than chrysazin . The result was agreement
with that of the genotoxicity assay with hepatocytes . It appears that genotoxicity in
rodent hepatocytes is more consistent with mammalian carcinogenesis than bacterial
mutagenicity for these anthraquinone chemicals .
385
EVALUATION OF CLASTOGENICITY OF NON-PHYSIOLOGICAL PHs IN CULTURED MAMiALIAN CELLS .
MORITA, T ., TAKEDA, K ., and OKUMURA, R ., Tokyo Research Laboratories,
NIPPON GLAXO LTD ., Nerima-ku, Tokyo, Japan .
Using Chinese hamster ovary K1 cells, chromosomal aberration tests were carried
out of formic acid, acetic acid, lactic acid and a mixture of S9 and NaOH, and the
relationship between pHs of the media and their clastogenic activity was examined .
The medium used was Ham"s F12 supplemented with 17 mM NaHC03 and lOx FCS . All of
these acids induced chromosomal aberrations at the initial pH of ca . 6 .0 or below
(10-14 mM of each acid) either in the presence or absence of S9 mix . Exposures of
cells to pH 5 .7 or below (12-16 mM of each acid) were found toxic . In the culture
media which were first acidified with each of these acids and then neutralized to
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1989 EMS Abstracts 133
Notes