Effects of vitamin K2 (menatetrenone) on calcium balance in ovariectomized rats

Jpn J Pharmacol. 2002 Jan;88(1):55-61. doi: 10.1254/jjp.88.55.


Vitamin K2 (menatetrenone) has been used for the treatment of osteoporosis in Japan. We investigated the effects of ovariectomy (OVX) and vitamin K2 on the calcium (Ca) balance in 20-week-old female Fischer rats. Vitamin K2 (31 mg/kg per day) was given to animals as a dietary supplement. At weeks 4 and 8 after OVX, a Ca balance study was performed for 5 days. The intestinal Ca transport was determined using the everted gut-sac technique at week 9. The Ca balance was poorer in the OVX-control group than in the sham-control group at weeks 4 and 8 after OVX. The Ca balance improved significantly in the vitamin K2 groups as compared with the sham- and OVX-control groups. The intestinal Ca transport decreased due to OVX and was higher in the vitamin K2 administration groups than in the sham- and OVX-control groups, but not to a significant extent. The bone mineral density in the femoral metaphysis as well as the cortical area and cortical thickness in the femoral diaphysis in the OVX-control group were lower than in the sham-control group. The administration of vitamin K2 significantly inhibited an OVX-induced decrease in cortical area and cortical thickness in the femur. These findings suggest that the poor Ca balance observed in ovariectomized rats may be improved by vitamin K2; vitamin K2 may be involved in preventing bone loss in vivo.

MeSH terms

  • Animals
  • Biological Transport
  • Body Weight / drug effects
  • Bone Density / drug effects
  • Calcium / metabolism*
  • Calcium / urine
  • Feces / chemistry
  • Female
  • Femur / anatomy & histology
  • Femur / drug effects
  • Femur / metabolism
  • Homeostasis / drug effects
  • Intestinal Mucosa / metabolism
  • Intestines / drug effects
  • Organ Size / drug effects
  • Osteoporosis / metabolism
  • Ovariectomy*
  • Rats
  • Rats, Inbred F344
  • Uterus / drug effects
  • Uterus / metabolism
  • Vitamin K 2 / analogs & derivatives*
  • Vitamin K 2 / pharmacology*


  • Vitamin K 2
  • menatetrenone
  • Calcium