Ethanol (EtOH) was evaluated as a known positive in the RACB protocol using CD-1 mice. A dose-range finding study provided data on water consumption, body weights, and clinical signs, which were used to select concentrations for the continuous cohabitation phase (Task 2) of 5, 10, and 15% w/v in distilled water. Water consumption was reduced at the middle and highest concentrations, by nearly equal to 9% and 25%, respectively. Interestingly, body weights remained unchanged during the course of Task 2. These concentrations, consumption, and body weight data produced calculated consumption estimates of nearly equal to 8.5, 16.0, and 20 g/kg/d.
While the mean number of litters/pair was unchanged by EtOH consumption, the number of live pups/litter was reduced by nearly equal to 20% at the high dose. Viability, sex ratio, and pup body weight (absolute or adjusted for litter size) was unaffected by EtOH consumption.
It was concluded that EtOH was causing no significant reproductive toxicity during Task 2, so a Task 3 crossover was not performed, and second generation effects (Task 4) were evaluated in the control and high dose groups only.
The last litter from the control and 15% EtOH groups was nursed by the dam until weaning at pnd 21, then provided with the same dosed water as their parents. While the viability of the F1 pups was unaffected by parental EtOH exposure, body weight was reduced by nearly equal to 25% at weaning. At the time of mating (nearly equal to pnd 74), male and female body weights in the 15% EtOH group were 13% and 7% less than their respective controls.
EtOH did not affect the proportion of F1 pairs mating or delivering live young, and the number and viability of those young were also unchanged. The weight of the F2 pups, adjusted for litter size, was reduced in the EtOH-exposed group by nearly equal to 7%.
After the F2 pups were evaluated, all animals were killed, and the F1 parents were necropsied. For the EtOH-exposed group, male terminal body weight was 10% less than controls. Absolute testis weight was unchanged, while adjusted weights of liver and kidneys were increased in the EtOH-exposed mice by 11% and 12%, respectively. Epididymal sperm motility was reduced from a control value of 80% motile, to 55% in the EtOH-consuming group; there were no changes in epididymal sperm density or morphologic abnormalities. Female mice consuming 15% EtOH weighed 8% less than controls at sacrifice, while adjusted liver weight and kidney weight was increased by 13% and 11%, respectively.
In summary, ethanol, at concentrations sufficient to affect water consumption more than body weight, had only modest reproductive effects (reduced sperm motility) in Swiss mice. These effects mirror those found in literature reports.