title: Additive effect of vitamin K2 and risedronate on long bone mass in hypophysectomized young rats.
abstract: Hypophysectomy (HX) arrests bone growth and induces osteopenia in the long bones of rats. The present study investigated the combined effect of vitamin K(2) and risedronate on long bone mass in HX rats, in order to determine whether treatment with these two agents had an additive effect. Forty female Sprague-Dawley rats were hypophysectomized at 6 weeks of age by the supplier, and were shipped to our laboratory at three days after surgery along with ten intact rats that served as age-matched controls. The study was started on the day when the rats were received. Three HX rats were excluded from the study because of the failure of HX. Forty-seven rats (6 weeks old) were assigned to the following 5 groups by the stratified weight randomization method: intact controls, HX alone, HX + vitamin K(2) (30 mg/kg, p.o., daily), HX + risedronate (2.5 microg/kg, s.c., 5 days a week), and HX + vitamin K(2) + risedronate. The dosing period was 4 weeks. HX resulted in a decrease of the femoral bone area, bone mineral content (BMC) and bone mineral density (BMD), as well as a decrease in the cancellous bone mass of the proximal tibial metaphysis and the total tissue and cortical areas of the tibial diaphysis. These changes were associated with a marked reduction in the serum level of insulin like growth factor (IGF)-I and with elevation of serum alkaline phosphatase (ALP) and pyridinoline. Administration of vitamin K(2) increased the serum ALP level in HX rats, but did not affect any of the other parameters. On the other hand, risedronate ameliorated the decrease of femoral BMD and cancellous bone mass at the proximal tibial metaphysis in HX rats without affecting the serum IGF-I level, as a result of not causing a significant elevation of serum pyridinoline. Vitamin K(2) and risedronate combined had an additive effect on the femoral bone area, BMC and BMD, and the combined treatment group did not show any significant reduction of the total tissue and cortical areas at the tibial diaphysis, as well as a reduced serum pyridinoline level compared with untreated rats and an increased serum ALP level compared with untreated or risedronate-treated rats. These results suggest that risedronate had a positive effect on the BMD and cancellous bone mass of long bones in HX rats. Despite the lack of a significant effect of vitamin K(2) on bone mass parameters, it had an additive effect with risedronate on the BMC, BMD and cortical bone mass of long bones in HX rats.
authors: Department of Sports Medicine, Keio University School of Medicine, Tokyo, Japan.
authors: Jun
authors: J
authors: Iwamoto
authors: Tsuyoshi
authors: T
authors: Takeda
authors: Yoshihiro
authors: Y
authors: Sato
authors: James K
authors: JK
authors: Yeh
mesh_terms: D000469:Alkaline Phosphatase / Q000097:blood; D000596:Amino Acids / Q000097:blood; D000818:Animals; D015519:Bone Density / Q000187:drug effects*; D050071:Bone Density Conservation Agents / Q000494:pharmacology*; D001842:Bone and Bones / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D004357:Drug Synergism; D012968:Etidronic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D005269:Femur / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D007016:Hypophysectomy; D007091:Image Processing, Computer-Assisted; D007334:Insulin-Like Growth Factor I; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D000068296:Risedronic Acid; D013977:Tibia / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D024482:Vitamin K 2 / Q000494:pharmacology*; D014815:Vitamins / Q000494:pharmacology*
chemical_list: D000596:Amino Acids; D050071:Bone Density Conservation Agents; D014815:Vitamins; D024482:Vitamin K 2; C015484:pyridinoline; D007334:Insulin-Like Growth Factor I; D000469:Alkaline Phosphatase; D000068296:Risedronic Acid; D012968:Etidronic Acid