Evidence for vitamin D dependent gamma-carboxylation in osteocalcin related proteins.

The content of gamma-carboxyglutamic acid (gla) was determined in rat femoral bone and kidney cortex in rachitic and vitamin D treated animals. It was demonstrated that the level of gla is decreased in vitamin D depleted animals both in kidney cortex and femoral bone. Supplementation of vitamin D deprived animals with this vitamin resulted in an increase in the gla concentration to almost normal levels. Also the incorporation of 14C NaHCO3 in renal cortex microsomes from rachitic animals was blocked. It is suggested that the absence of gla resulted from the direct action of vitamin D on mRNA for the Ca-binding protein.