title: Collaborative work on evaluation of ovarian toxicity. 5) Two- or four-week repeated-dose studies and fertility study of busulfan in female rats.
abstract: Busulfan, an antineoplastic agent that targets small follicles (primordial and primary follicles), was given orally to female Sprague-Dawley rats (0, 0.1, 0.5, or 1.5 mg/kg/day; n = 10 in each group) for 2 or 4 weeks to assess the optimal administration period for detection of the toxic effects on ovarian morphology. Isolated ovaries were used for histopathological analysis and follicle counts. In addition, a female fertility study was conducted by giving the same dose levels of busulfan from 2 weeks before mating to day 7 of pregnancy to determine the non-observed-adverse-effect-level (NOAEL) for female reproduction. In the 2-week study, all rats treated with busulfan showed normal estrous cyclicity and no toxicological changes in weight or histopathology of the ovaries. In the 4-week study, a decrease in small follicles was found histopathologically in 1 rat, even at 0.5 mg/kg, and in 4 rats at 1.5 mg/kg. Proliferating cell nuclear antigen immunohistochemistry of the follicles confirmed the above decrease in number of small follicles at 1.5 mg/kg. In the female fertility study, increases in dead embryos and post-implantation loss were found in rats at 1.5 mg/kg. Taken together, the NOAELs were 1.5 mg/kg for reproductive performance and 0.5 mg/kg for early embryonic development. In conclusion, the present study indicates that a 4-week administration period and appropriate assessment, including careful histopathological analysis of stage-based follicles are needed to detect small follicle depletion in a general toxicity study used as a first-titer screen.
authors.affiliation: Research Center, Kyorin Pharmaceutical Co., Ltd., Simotsuga-gun, Tochigi, Japan. yousuke.sakurada@mb.kyorin-pharm.co.jp
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Sakurada
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kudo
authors.forename: Shogo
authors.initials: S
authors.lastname: Iwasaki
authors.forename: Yuki
authors.initials: Y
authors.lastname: Miyata
authors.forename: Miyuki
authors.initials: M
authors.lastname: Nishi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Masumoto
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000008:administration & dosage / Q000633:toxicity*; D015415:Biomarkers / Q000378:metabolism; D002066:Busulfan / Q000008:administration & dosage / Q000633:toxicity*; D004334:Drug Administration Schedule; D020964:Embryo Loss / Q000139:chemically induced; D004622:Embryo, Mammalian / Q000187:drug effects; D047108:Embryonic Development / Q000187:drug effects; D030762:Estrous Cycle / Q000187:drug effects; D005260:Female; D005298:Fertility / Q000187:drug effects*; D007564:Japan; D008297:Male; D019055:No-Observed-Adverse-Effect Level; D009929:Organ Size / Q000187:drug effects; D006080:Ovarian Follicle / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010053:Ovary / Q000187:drug effects* / Q000473:pathology; D011247:Pregnancy; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D055818:Public-Private Sector Partnerships; D051381:Rats; D017207:Rats, Sprague-Dawley; D012958:Societies, Scientific; D018675:Toxicity Tests / Q000379:methods*
chemical_list: D018906:Antineoplastic Agents, Alkylating; D015415:Biomarkers; D018809:Proliferating Cell Nuclear Antigen; D002066:Busulfan