Reproductive capacity and dominant lethal mutations in female guinea-pigs and Djungarian hamsters following X-rays or chemical mutagens.

The reproductive capacity and induction of dominant lethal mutations in adult female guinea-pigs and Djungarian hamsters were tested following treatment with 400 rad X-rays, 1.6 mg/kg triethylenemelamine (TEM) or 75 mg/kg isopropylmethanesulphonate (IPMS). A fairly high level of dominant lethals were observed in female guinea-pigs mated at the first oestrus after irradiation (23.4 +/- 6.4%) with a lower yield at 3 months (9.6 +/- 8.2%). Neither of the chemicals caused any significant induction of dominant lethals at either mating time. In the reproductive capacity experiments, the mean litter size of irradiated female guinea-pigs was reduced for about 12 months and this was especially marked in the first 6 months following treatment. Neither of the chemicals caused any significant differences in early litter sizes but there was a noticeable reduction in the litter sizes of TEM-treated females in the 18--24 month interval. With Djungarian hamsters a marked effect of X-rays on reproductive capacity was apparent. After 400 rad a smaller proportion of irradiated females littered in the first 25-day interval than after the other treatments, and no irradiated females produced more than one litter. Neither of the chemicals caused such a drastic reduction in fertility but TEM-treated females produced fewer litters and became sterile at an earlier age than control or IPMS-treated females. With IPMS, the number of litters produced was similar to the controls. Both chemicals caused a significant reduction in litter-size but further work is needed to establish whether this was due to induction of dominant lethals. No translocations were observed in the sons of treated female guinea-pigs or hamsters, but the numbers of animals studied were too small for any conclusions to be drawn.