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Species differences in the outcome of the Ames test with 4 promutagens and S9 liver preparations from 3 animal species and man
195 6O Joosten, H.F.P., and T.D. Yih, Organon International B.V., Drug Safety R&D Labs, Oss (The Netherlands) Species differences in the outcome of the Ames test with 4 promutagens and $9 liver preparations from 3 animal species and man
With the aim to find the most suitable animal species for the preparation of liver $9 fractions, Wistar rats, Swiss mice and Dutch rabbits were studied. Animals were untreated or Aroclor-induced. Human liver $9 was included for comparison. The plate test was performed according to Ames using 1, 5, 10, 20 and 30% $9 in the $9 mix. The promutagens benzo[a]pyrene (BP, 7.5 /~g), 2-aminoanthracene (2-AA, 1 ~g), cyclophosphamide (CP, 200 #g) and N-nitrosopyrrolidine (NP, 5 mg) and Salmonella typhimurium strains TA1535 and TA1538 were used. Except with 2-AA, Aroclor treatment enhanced the mutagenic response. With some exceptions the number of revertants increased with higher $9 concentrations. The mutagenic response obtained with human $9 was very slight with BP and CP, low with NP and moderate with 2-AA. Within the control and Aroclor series rabbit $9 was, in general, the most active $9 preparation. Replacement of Aroclor-induced rats by untreated rabbits for the preparation of liver $9 is considered for routine Ames testing.
61 Kaina, B., Zentralinstitut ftir Genetik und Kulturpflanzenforschung der AdW der DDR, 4325 Gatersleben (G.D.R.) Adaptation of V79 Chinese hamster cells to low doses of monofunctionai aikylating agents
Exposure of V79 cells to a single low (subtoxic, subclastogenic) dose of N-methylN-nitrosourea (MNU) or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) reduced the cytotoxic, mutagenic, and clastogenic effects of the same agents applied 6 h later. Cytotoxicity (colony-forming ability) was measured in pretreated (e.g., MNU, 5/~M; MNNG, l nM) and not pretreated cells and was shown to be enhanced, under optimal conditions of pretreatment, by nearly 2-fold. When cells were pre-exposed to these very low mutagen doses the frequency of 6-thioguanine-resistant cells induced by a challenge dose of either MNU (0.1-0.25 mM) or MNNG (0.1-0.4/~M, 60-min treatment) decreased strongly as compared to the non-pretreated control. The degree of 'adaptation', i.e., increase of cell survival and decrease of the frequency of 6-thioguanine-resistant cells, proved to be dependent on the mutagen concentration used for pretreatment. The effect of subclastogenic doses of MNU (30-100 /tM) or MNNG (50-500 nM) on the yield of chromosomal aberrations induced by a challenging dose of the same mutagen (0.6 mM MNU or 20 ~M MNNG, 60-min treatment) has also been
With the aim to find the most suitable animal species for the preparation of liver $9 fractions, Wistar rats, Swiss mice and Dutch rabbits were studied. Animals were untreated or Aroclor-induced. Human liver $9 was included for comparison. The plate test was performed according to Ames using 1, 5, 10, 20 and 30% $9 in the $9 mix. The promutagens benzo[a]pyrene (BP, 7.5 /~g), 2-aminoanthracene (2-AA, 1 ~g), cyclophosphamide (CP, 200 #g) and N-nitrosopyrrolidine (NP, 5 mg) and Salmonella typhimurium strains TA1535 and TA1538 were used. Except with 2-AA, Aroclor treatment enhanced the mutagenic response. With some exceptions the number of revertants increased with higher $9 concentrations. The mutagenic response obtained with human $9 was very slight with BP and CP, low with NP and moderate with 2-AA. Within the control and Aroclor series rabbit $9 was, in general, the most active $9 preparation. Replacement of Aroclor-induced rats by untreated rabbits for the preparation of liver $9 is considered for routine Ames testing.
61 Kaina, B., Zentralinstitut ftir Genetik und Kulturpflanzenforschung der AdW der DDR, 4325 Gatersleben (G.D.R.) Adaptation of V79 Chinese hamster cells to low doses of monofunctionai aikylating agents
Exposure of V79 cells to a single low (subtoxic, subclastogenic) dose of N-methylN-nitrosourea (MNU) or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) reduced the cytotoxic, mutagenic, and clastogenic effects of the same agents applied 6 h later. Cytotoxicity (colony-forming ability) was measured in pretreated (e.g., MNU, 5/~M; MNNG, l nM) and not pretreated cells and was shown to be enhanced, under optimal conditions of pretreatment, by nearly 2-fold. When cells were pre-exposed to these very low mutagen doses the frequency of 6-thioguanine-resistant cells induced by a challenge dose of either MNU (0.1-0.25 mM) or MNNG (0.1-0.4/~M, 60-min treatment) decreased strongly as compared to the non-pretreated control. The degree of 'adaptation', i.e., increase of cell survival and decrease of the frequency of 6-thioguanine-resistant cells, proved to be dependent on the mutagen concentration used for pretreatment. The effect of subclastogenic doses of MNU (30-100 /tM) or MNNG (50-500 nM) on the yield of chromosomal aberrations induced by a challenging dose of the same mutagen (0.6 mM MNU or 20 ~M MNNG, 60-min treatment) has also been