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Most rodent reproductive toxicology studies utilize strains of high fecundity. These studies were conducted to examine the possibility that mouse strains of differing fecundity would respond differently to a known reproductive toxicant. Thirty pairs each of Swiss CD-1, C57B1, and C3H mice were cohabited for 14 weeks while consuming 0, 0.03, 0.10, or 0.30% EGME in the drinking water. Litter data were collected during cohabitation. Body and organ weights, and various sperm data, were collected at necropsy, and second-generation fertility was evaluated. The data show that the most fecund strain (Swiss) was affected the least by exposure to EGME, while the least fecund strain (C3H) suffered the greatest declines in fertility. These differences might alter interspecies extrapolation factors, or the permissible exposure levels for humans. [ABSTRACT FROM PUBLISHER]

Many test compounds used in toxicity studies produce a “systemic” toxicity manifested as reduced body weight gain. While it is known that reduced weight gain during juvenile growth reduces or delays reproductive competence, the effects of adultonset feed restriction (FR) and inhibited weight gain on the reproductive system of mice are poorly known. To gain some information on the effects of graded body weight reduction, or reduced body weight gain, on commonly used reproductive end-points, the studies reported below were conducted at two laboratories, using adult mice that were maintained at 90, 80, and 70% of concurrent control body weight (CBW) for up to 21 weeks. Estrous cyclicity and fertility in the females were significantly affected. While male fertility was variably affected, there was a significant decrease in the number of epididymal sperm and in the number of testicular spermatids in the 70% CBW groups. Testis weight was conserved in both studies; relative testis weight increased in all FR groups. These data can improve the interpretation of future studies by helping to separate chemically induced changes from those produced by reduced body weight gain. [ABSTRACT FROM PUBLISHER]