[The changes of bone phosphoproteins in vitamin D-deficiency and aging in vivo]

Phosphoproteins were partially purified from vitamin D-deficient and various aged chicken bones. The bones were first extracted with EDTA and fractionated using DEAE-Sephacel anion exchange chromatography and Sephacryl S-300 molecular sieving chromatography. The major phosphoproteins were eluted in two different peaks on a DEAE chromatogram. The front peak contained low phosphorylated proteins and the other contained highly phosphorylated proteins. The total amount of phosphoproteins in vitamin D-deficient bone was lower than that in normal bone. The decrease of low phosphorylated proteins was especially obvious. On the other hand, molecular weights, amino acid compositions and the degree of phosphorylation were almost the same in both normal and vitamin D-deficient chick bone. The total extracted weight of phosphoproteins and the molecular weights on SDS-PAGE of partially purified phosphoproteins in each aged chick bone decreased with aging. These results suggest that the production of phosphoproteins is regulated by vitamin D and the degradation of phosphoproteins is an important factor in the progress and the maturation of calcification.