ENZYMES OF PROTEIN AND PHOSPHATE CATABOLISM IN RAT BONE .2. CHANGES IN VITAMIN D DEFICIENCY

The effect of vitamin D deficiency on growth, serum ions and bone enzymatic activity has been studied in rats. The diet contained 0.6% calcium and 0.6% phosphorus. Omission of vitamin D from the diet resulted in decreased growth, decreased metaphyseal bone ash, decreased serum calcium and increased serum phosphorus. Changes in enzymatic activity in metaphyseal and diaphyseal bone from the tibia and femur also occurred. Alkaline phosphatase, acid β-glycerophosphatase, proteolytic activity at pH 8.0, leucine aminopeptidase, and glutamate dehydrogenase were increased in metaphyseal bone samples. Lactate dehydrogenase and acid phenylphosphatase were decreased. Similar changes in bone enzymatic activity occurred in the diaphysis except that the lactate dehydrogenase and acid phenylphosphatase activities were not decreased and proteolytic activity at pH 5.6 was increased. The vitamin D deficiency did not affect aspartate or alanine transaminase or proteolytic activity at pH 3.7. These enzyme changes were not due to decreased food consumption because they did not occur in pair-fed animals. There was no lack of degradative enzymes that would impair bone resorption and lead to a fall in serum calcium. Rather the results were more consistent with an increase in bone resorption. © 1969 Springer-Verlag.