title: Comparison of growth and pubertal progression in wild type female rats with different bedding types.
abstract: OBJECTIVE
  Endocrine-disrupting chemicals interfere with the endocrine system and therefore affect growth and pubertal progression. The study aim was to compare the growth and pubertal progression in wild-type female rats with different bedding types.
  
  
  METHODS
  Twenty 5-week-old female wild-type Sprague Dawley rats were randomly assigned to two groups with different bedding types: one group received wood shaving bedding, while a second group received corncob bedding. We determined crown-rump length and body weight as anthropometric measurements and assessed the serum growth hormone (GH) and estradiol levels. The gh1 mRNA expression levels were compared using quantitative real time transcription polymerase chain reaction. The estrous cycle was evaluated by vaginal smear.
  
  
  RESULTS
  The anthropometric measurements were not significantly different between the two groups. The mean relative expression of the gh1 gene was lower in the corncob bedding group than that in the wood shaving group (P=0.768). Meanwhile serum GH and estradiol were increased in the wood shaving bedding group; however this difference was not statistically significant. The time to first estrus and the length of the estrous cycle were increased in the corncob bedding group; the proportion of normal estrous cycles was also decreased. These findings indicate irregularities in the estrous cycle.
  
  
  CONCLUSIONS
  Endocrine-disrupting chemicals in corncob bedding might be associated with time to first estrus and length of the estrous cycle. Therefore, the type of bedding should be considered as a factor affecting pubertal progression in rodents.
authors.affiliation: Department of Pediatrics, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors.forename: Byung Ho
authors.initials: BH
authors.lastname: Kang
authors.affiliation: Department of Pediatrics, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea.
authors.forename: Shin-Hee
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Pediatrics, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea.
authors.forename: Kyung A
authors.initials: KA
authors.lastname: Jung
authors.affiliation: Department of Pediatrics, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea.
authors.forename: So Youn
authors.initials: SY
authors.lastname: Kim
authors.affiliation: Department of Pediatrics, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors.forename: Sung-Hoon
authors.initials: SH
authors.lastname: Chung
authors.affiliation: Department of Pediatrics, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors.forename: Young Shil
authors.initials: YS
authors.lastname: Park
authors.affiliation: Department of Pediatrics, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors.forename: Kyung Lim
authors.initials: KL
authors.lastname: Yoon
authors.affiliation: Department of Pediatrics, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors.forename: Kye Shik
authors.initials: KS
authors.lastname: Shim
keywords: Bedding; Endocrine disrupting chemicals; Growth; Puberty