A new approach to dominant lethal testing

Abstract

Male weanling rats were given triethylenemelamine (TEM) at 0.025, 0.050, or 0.075 mg/kg and male adult rats were given TEM at 0.050 mg/kg, all by gavage 5 days/week for 10 weeks. At the end of the treatment period, the animals were immediately cohoused with two females each during Week 1 and with two other females during Week 2. The females were sacrificed 14 days from the midweek of cohousing, and the numbers of corpora lutea and live and dead implantations were counted. Statistical analyses of the number of dead implantations per pregnant female and of the number of females with one or more dead implantations or with two or more dead implantations indicated significant increases in all indexes for the adults and a more variable response on the part of the weanlings. The results from this study indicate that there is no loss of pertinent information by employing this approach except that of stage sensitivity. It reduces the amount of data usually required and assesses the more significant dominant lethal effect, that of postimplantation loss.