The involvement of phosphohydrolases in mineralization: studies on enzymatic activities extracted from red deer...

The process of growth of red deer antler "bone" is very similar to the endochondral growth of long bones. The growth zones of the antler are temporally organized from the tip, in a proximal direction, permitting sequential aspects of antler development to be followed in serial transverse sections from the tip to the base. The activities of alkaline phosphatase (ALKPase, phosphodiesterase I, nucleoside triphosphate pyrophosphohydrolase, and 5'-nucleotidase were measured in extracts of antler mineralizing tissue at different distances from the tip, and compared with mineralization, which peaked at ca. 60 mm. The activities of ALKPase and phosphodiesterase I were maximal at ca. 30 and 60 mm, respectively, suggesting that these enzymes are involved in different phases of mineralization. The patterns of distribution were similar to those determined from equivalent quantitative histochemical analyses, confirming the validity of both methods of assessment. The distribution of nucleoside triphosphate pyrophosphohydrolase also suggested that this enzyme is involved in mineralization, but the pattern of distribution was not as reproducible as for the other enzymes. 5'-Nucleotidase activity was distributed differently than the others and showed relatively constant levels at all distances. The results suggest that each of the four phosphohydrolases may have a different role in the process of mineralization. A tentative model suggesting functions for these phosphohydrolases and ATPases is presented and discussed.