AimTo explore the effect of Vitamin K2 on vascular calcifiction in old ovariectomized rats model.MethodsThirty-six ten months female SD rats were allocated into three groups randomly: sham operation group, ovariectomized (OVX) group and OVX＋Vitamin K2 (OVX＋VK2) group.Rats in OVX＋VK2 group were administered orally with Vitamin K2 (30 mg(kg·d), 5 times a week) after three weeks of ovariectomy for 12 weeks.The urine and serum of all rats were kept every three weeks.All rats were sacrificed after 18 weeks, uterus and arteries were observed by histochemical method.The contents of MGP in serum and urine were determined by enzyme-linked immunosorbent assay (ELISA).Relative quantification of MGP mRNA expression in arterial was detected by Fluorescent real-time quantitative reverse-transcription polymerase chain reaction.Expression of ucMGP was detected by immunochistochemistry.Aterial calcification was evaluated by Von Kossa staining.The content of arterial calcium was measured.ResultsAfter 18 weeks of ovariectomized, the pathological section of uterus and aortic had differernt variation in different groups.The content of estrogen in serum had no difference before ovariectomized.Before sacrifice, the content of estrogen of sham group had no change, the other groups reduced (p<0.05).The content of MGP in serum and urine had no difference before ovariectomized, the content of MGP in serum and urine decreased in OVX group, the content of MGP in serum and urine decreased and then increased in OVX＋VK2 group.Relative quantification of MGP mRNA expression of aterial in OVX＋VK2 group was significantly lower than sham group (p<0.01), and was higher than that in OVX group (p<0.01).