title: Effect of vitamin K2 on cortical and cancellous bones in orchidectomized young rats.
abstract: OBJECTIVE
  The purpose of the present study was to compare the effect of vitamin K(2) on cortical and cancellous bones in orchidectomized young rats.
  
  
  METHODS
  Forty male Sprague-Dawley rats, 6 weeks of age, were randomized by stratified weight method into four groups with 10 rats in each group: baseline controls (BLC), age-matched controls (AMC), orchidectomy (ORX), and ORX+vitamin K(2) administration (K). Vitamin K(2) (menatetrenone) was administered subcutaneously twice a week at dose of 30 mg/kg each. The experimental period was 8 weeks, and cortical and cancellous bone histomorphometry was performed on the tibial shaft and the proximal tibia, respectively.
  
  
  RESULTS
  Cortical area (Ct Ar) and cancellous bone volume (BV/TV) were significantly greater in the AMC group than in the BLC group. Ct Ar was significantly lower in the ORX group than in the AMC group, and cancellous BV/TV was also significantly lower in the ORX group than in the AMC group as a result of significantly increased eroded surface (ES/BS). Although Ct Ar in the ORX+K group did not differ significantly from that in the ORX group, cancellous BV/TV was significantly greater in the ORX+K group than in the ORX group, but still significantly lower than in the AMC group. This protective effect of vitamin K(2) on cancellous bone was attributable to normalizing increased ES/BS.
  
  
  CONCLUSIONS
  Vitamin K(2) appears to act more strongly on cancellous bone than on cortical bone in ORX young rats. High dose vitamin K(2) could partially prevent the reduction of cancellous bone gain by normalizing raised bone resorption in ORX young rats.
authors.affiliation: Department of Sports Medicine, Keio University School of Medicine, Tokyo, Japan. jiwamoto@sonata.plala.or.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Iwamoto
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Takeda
authors.forename: James K
authors.initials: JK
authors.lastname: Yeh
authors.forename: Shoichi
authors.initials: S
authors.lastname: Ichimura
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Toyama
mesh_terms: D000818:Animals; D015519:Bone Density; D001862:Bone Resorption; D001842:Bone and Bones / Q000187:drug effects*; D008297:Male; D009919:Orchiectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013977:Tibia / Q000187:drug effects; D024482:Vitamin K 2 / Q000031:analogs & derivatives / Q000494:pharmacology*
chemical_list: D024482:Vitamin K 2; C030814:menatetrenone