title: Intrauterine position and postnatal growth in Sprague-Dawley rats and ICR mice.
abstract: In rodents, steroid hormones are thought to be transported between adjacent fetuses, and male or female fetuses that develop in utero between female fetuses may have higher serum levels of estradiol, and lower serum levels of testosterone, relative to siblings of the same sex that develop between two male fetuses. The consequence in the variation of postnatal growth, development, and function in the intrauterine position, using various parameters such as anogenital distance, preputial separation and vaginal opening, estrous cycle, locomotor activity, and growth of reproductive organs, were examined in Sprague-Dawley rats. ICR mice were treated with 17beta-estradiol before copulation and during pregnancy to address the interaction with endogenous estradiol during pregnancy. In rats, no evidence of effects of prior intrauterine position was observed for any of the parameters examined. Mouse fetal exposure via the mother to low-dose 17beta-estradiol revealed no changes in the rate of postnatal growth in males and females that developed in any intrauterine position in utero. The results of this study suggested that the intrauterine position of the embryos/fetuses did not affect the postnatal growth of the reproductive organs, sexual maturation, or behavior in rats and mice.
authors.affiliation: Department of Life Science, Faculty of Science and Technology, Kinki University, Kowakae 3-4-1, Higashiosaka, Osaka 577-8502, Japan. tnagao@msa.kindai.ac.jp
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Nagao
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Wada
authors.forename: Makiko
authors.initials: M
authors.lastname: Kuwagata
authors.forename: Madoka
authors.initials: M
authors.lastname: Nakagomi
authors.forename: Chiaki
authors.initials: C
authors.lastname: Watanabe
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Yoshimura
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Saito
authors.forename: Kenji
authors.initials: K
authors.lastname: Usumi
authors.forename: Jun
authors.initials: J
authors.lastname: Kanno
mesh_terms: D001003:Anal Canal / Q000033:anatomy & histology; D000818:Animals; D004958:Estradiol / Q000633:toxicity; D004971:Estrus; D005260:Female; D005324:Fetal Movement; D020567:Fetal Weight; D005333:Fetus / Q000502:physiology*; D005835:Genitalia / Q000033:anatomy & histology; D006128:Growth; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009043:Motor Activity; D009929:Organ Size; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012741:Sexual Maturation
chemical_list: D004958:Estradiol