The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings were not evaluated in accordance with the levels of evidence for reproductive or developmental criteria established by NTP in March 2009. The findings and conclusions for this study should not be construed to represent the views of NTP or the U.S. Government.
"Reproductive Assessment by Continuous Breeding" (RACB) protocol was originally designed using mice as the test species. The purpose of the present study was to develop a RACB protocol in CD Sprague-Dawley rats. Ethylene glycol monomethyl ether (EGMME), a known reproductive toxicant, was used as the test article. Dose levels selected were 0.006, 0.012, and 0.024%, administered via drinking water. Male and female rats (20 pairs per treatment group, 40 pairs of control animals) were continuously exposed for a 7-day precohabitation period and 112-day cohabitation (Task 2).
While there was no decrease in average litter size with increased dose, the number of live male pups per litter and the total number of pups per litter were decreased in the 0.024% group. Both absolute and adjusted live pup weight were increased in all EGMME groups, but this was not dose-related. During the cross-over mating to determine the affected sex, there were fewer live male pups born to the 0.024% male X control female pairs. During the mating trial for the second generation, fewer male and total pups were delivered in the high-dose group, and both absolute and adjusted pup weight were increased in the middle and high dose groups. Low control fertility (63% fertile) during the cross-over mating is a cause for concern, however suggested protocol changes should alleviate some of this problem. Thus the RACB protocol can successfully be adjusted for use in rats.
NTIS # PB90252321