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Mutagenicity studies on ethylenethiourea. II. Cytogenetic analysis The cytogenetic effect of ethylenethiourea (ETU) was studied in vitro with a chinese hamster cell line (DON) and in vivo with bone-marrow cells of rats. Male and female rats of the Wistar Imamichi strain, both 3 and 10 weeks of age, received a single or successive oral administration of the chemical. In vitro study. Cells were treated with the chemical for 6, 24 and 48 h at the concentration of 1.0 or 3.2 mg/kg that caused clear inhibition of cells growth. But they showed no significant increase in chromosomal abnormalities. In vivo study rats 10 weeks old received a single injection of ETU at 1000 mg/kg, 5 injections of 100 mg/kg or 3 injections of 200 mg/kg. The incidence of chromosomal abnormalities did n o t differ from the control values which showed a b o u t 0.5% aberrations. Three-week-old rats received a single administration of 200 or 400 mg/kg, 5 injections of 50 and 100 mg/kg, 3 injections of 150 or 200 mg/kg, or 2 injections of 400 mg/kg. Although there was no increase of morphological aberrations, numerical abnormalities increased slightly in the high dose groups that had received a single injection of 200 or 400 mg/ kg, 5 injections of 100/kg, 3 injections of 200 mg/kg or 2 injections of 400 mg/ kg.

24 Y. Shirasu, S. Teramoto and A. Shingu, The Institute of Environmental Toxicology, Kodaira-shi, T o k y o (Japan)

Mutagenicity studies on ethylenethiourea. III. Dominant-lethal assay Possible mutagenic activity of ethylenethiourea (ETU) was investigated in a dominant-lethal mutagenicity study with mice. Random-bred ICR male mice were used at 10 weeks of age. Groups of 15 males were ~rea~ed with ETU at 0, 300 or 600 mg/kg in daily oral doses for five days or ethylmethanesulphonate (EMS) at 300 mg/kg in a single i.p. dose. These animals were subsequently mated with untreated virgin females of the same stock for the following 5 weeks. The female mice were inspected daily by vaginal plugs and were killed on day 12 or 13 of pregnancy. The percentage of pregnant females among animals treated with either chemical was comparable to that for the control, though one male given EMS became infertile after 2 weeks of testing. For the animals treated with ETU, the mean numbers of corpora lutea, implantation sites and live fetuses were much the same as for the control matings. No significant increase of the mutation rates was noted at any stage of spermatogenesis. Mutagenic effects were observed after treatment with EMS. The numbers of implantations and live fetuses per pregnancy decreased for the first 4 weeks in the group treated with EMS.

25 Y. Takizawa, R. Kurayama and I. Nakamura, Department of Public Health, School of Medicine, Akita University, Akita (Japan)

Mutagenicity studies on ethylenethiourea. III. Dominant-lethal assay [proceedings].

349 Mutagenicity studies on ethylenethiourea. II. Cytogenetic analysis The cytogenetic effect of ethylenethiourea (ETU) was studied in vitro with a c...
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