ARTICLE NO. FA972338 Differential Follicle Counts as a Screen for Chemically Induced Ovarian Toxicity in Mice: Results from Continuous Breeding Bioassays

sessment by Continuous Breeding (RACB) bioassays were used to directly compare differential ovarian follicle counts and reproduc-tive performance for 15 chemicals. Ovaries of 10 animals per group from 16 studies in CD-I.mice and 1 study each in C3H and C57BL/ 6 mice were sectioned serially at 6 /xm. Counts of small, growing, and antral follicles were obtained in every 10th section. For all follicle types, younger mice had more follicles than older mice, and CD-I mice had more follicles than age-matched animals from either inbred strain. The in-life portion of the RACB protocols demonstrated that 9 of 15 chemicals altered reproductive outcome in one or both sexes of mice, with six agents affecting females (R. E. Morrissey et al., 1989, Fundam. AppL Toxicol 13,747-777). Three of six female toxicants [2,2-bis(bromoethyl)-l,3-propaned-iol, BPD; ethylene glycol monomethyl ether, EGME; methoxyace-tic acid, MAA] significantly decreased counts of small and/or grow