Detection and measurement of vitamins K1 and K2 in human cortical and trabecular bone

Vitamin K plays an essential role in the gamma carboxylation of the gla-containing proteins of bone matrix, such as osteocalcin. We have measured the concentration of vitamin K1 (VK) and of the menaquinones MK-6, MK-7, and MK-8, the three major vitamin K2 moieties, in trabecular and cortical bone taken from the femoral neck of patients undergoing hip replacement. Both bone compartments were found to contain large amounts of VK, MK-6, MK-7, and MK-8. Concentrations were as high as those reported for the liver, the major storage organ for vitamin K. Further research is required to examine the association between vitamin K in bone and the gamma carboxylation of vitamin K-dependent bone proteins.