The Organic Matrix From Oyster Shell as a Regulator of Calcificationin Vivo

Exogenously supplied, C-l4 labeled organic matrix from oyster shell inhibited spicule formation by embryos of the sea urchin, Arbacia punctulata, as measured by simultaneous incorporation of inorganic C-14. Analysis of isolated spicules showed that the matrix reached the site of crystal growth and became incorporated into crystals. Comparison of the amount of matrix in spicules to inhibitory levels for matrix in an in vitro, pH-stat crystallization assay showed that the matrix became incorporated into spicules in an amount sufficient to account for the observed in vivo inhibition. The matrix did not act as a general metabolic inhibitor, as measured by respirometry, but rather seemed to have only the specific effect on spicule formation. Calculated and measured values of natural levels of matrix in spicules and urchin tests matched reasonably well with experimentally determined levels that regulated the rate of crystallization in vivo. Overall, the results support the idea that matrix fulfills a direct, regulatory role in biomineralization.