METHYL METHANESULFONATE (MMS) AS A RESOURCE CONSERVING AND RELIABLE POSITIVE CONTROL AGENT FOR MALE-RAT AND MALE-MOUSE DOMINANT LETHAL ASSAYS

A single i.p. injection of methyl methanesulphonate (MMS; 40 mg/kg) to male rats, followed by their sequential mating over 4-28 days post-do sing, was shown to induce dominant lethal (DL) effects in two strains of rats and in four separate experiments, Activity was evident between 4 days postdosing (sampling treated spermatozoa) and 28 days postdosi ng (sampling treated early spermatids). The highest incidences of reso rptions were seen between days 15 and 21 post-dosing, being similar to 1 week later than the peak of activity in the mouse. The DL effects s een were strong and could be detected as early as 4-10 days post-dosin g, at which time only small reductions in pregnancy rates and total im plantation numbers were seen, Similar, but weaker, mutagenic effects h ave been reported by Ehling et al, for MMS in mouse DL assays, These d ata indicate, therefore, that MMS provides a convenient positive contr ol agent for both male rat and male mouse dominant lethal assays, requ iring only approximately five treated males, each mated to two females at around 14 days post-dosing.