SIMILARITIES AND DIFFERENCES BETWEEN THE EFFECTS OF IPRIFLAVONE AND VITAMIN-K ON BONE-RESORPTION AND FORMATION IN-VITRO

The effects of ipriflavone and vitamin K on bone metabolism were exami ned using a culture system, Vitamin K-1 and vitamin K-2 (10(-7)M-10(-5 )M) inhibited both the activation of mature osteoclasts and the format ion of new osteoclasts without affecting the growth of progenitor cell s in cultures of mouse unfractionated bone cells, The inhibitory effec ts of vitamin K on bone resorption were similar to those of ipriflavon e and were not affected by the vitamin K antagonist warfarin, When ipr iflavone was added to the culture medium in combination with vitamin K -2, an additive inhibitory effect on bone resorption was observed. An additive effect was also observed in organ cultures of mouse calvaria, On the other hand, ipriflavone, but neither vitamin K-1 nor vitamin K -2, stimulated cellular alkaline phosphatase (ALP) activity on rat bon e marrow stromal cells under culture conditions in which cells subsequ ently form mineralized bone-like tissue, Vitamin K-1 and vitamin K-2 a lso did not modulate the stimulatory effect of ipriflavone on the ALP activity of the cells, These results suggest that the inhibitory effec ts of vitamin K on bone resorption are similar to those of ipriflavone through mechanisms that may be independent of the gamma-carboxylation system, while the effects of vitamin K on osteoblast phenotype expres sion are different from those of ipriflavone.