Studies on procedure for detecting mutagenicity of chemicals in Chinese hamster DON cells

346 Drug Research Center, Hatano, and * National Institute of Genetics, Mishima, Shizuoka-ken (Japan) Studies on procedure for detecting mutagenicity of chemicals in Chinese hamster DON cells A cell line of Chinese hamster lung cells, DON-6, was used for detecting the mutagenicity of EMS or MNNG. The re-plating m e t h o d was used to exclude the effect of cell-to-cell interaction (metabolic co-operation). Experiments were carried out under various conditions with different sizes of cell inoculum (5-50 X 104 cells/dish) and with different concentrations of 6-TG as selection agent (0.1-1 pg/ml). Induced mutation frequencies thus obtained fluctuated with different sizes of cell inoculum and concentrations of 6-TG. The mutation frequency in the control cultures decreased with increase in the number of replated cells. It was necessary, therefore, to examine the characteristics of 6-TG-resistant cells as to resistance to 6-TG, 8-AG or EMS. Two resistant cell clones obtained from the above re-plating experiments, ET-1031 and ET-0011, were examined. CH-252 cells of an 8-AG-resistant cell line isolated from the parental Chinese hamster cells isolated by Sekiguchi, were used for comparison with the above two cell lines. The ET-1031 and ET-0011 cells were resistant to 6-TG at the concentrations used for selection (0.1--0.3 pg/ml). They were also resistant to 8-AG. The levels of their resistances were nearly equal to those of CH-252 cells. The ET-1030 cells were resistant to EMS at the concentration of 1 X 10 -3 M used in the present re-plating method. We confirmed that resistance to these base analogs was stable after many cellular generations. Abbreviations: EMS, ethyl methanesulfonate; MNNG, N-methyl-NP-nitro-N-nitrosoguanidine; 6-TG, 2amino-6omercaptopurine; 8-AG, 8-azaguanine.

19 Y. Shimada, A. Murakami and Y. Tazima, National Institute of Genetics, Mishima, Sizuoka-ken (Japan) Dosimetric studies on the incorporation of furylfuramide into oocytes of the silkworm Furylfuramide (FF) is mutagenic in oocytes after treatment of mid-pupal silkworm with a dose of 9.6 or 19.2/zg/pupa (Tazima and Onimaru, 1974). The purpose of the present experiment was to estimate actual distribution and/or incorporation doses of FF received by oocytes as well as other tissues of the adult moth. This dosimetric study was carried out by using the oocytes of midpupal females treated with 14C-labelled FF (s.a., 1.2 mCi/mM). Females at 5--7 days before emergence having a body weight of 1.5 g per pupa were injected with 10 or 20/~g of [14C]FF per pupa. (The FF was dissolved in 0.5% CMC.) These doses were closely similar to those used for the mutagenic test of Tazima and Onimaru (1974). The distribution and/or incorporation doses of [14C]FF