A marked inhibition of the incorporation of S35-sulfate by normal calf costal cartilage was produced by potassium ascorbate in the presence of catalytic amounts of cupric ions. The effect of the various components of the ascorbic acid oxidizing system (potassium ascorbate, cupric ions, cuprous ions, hydrogen peroxide, dehydroascorbic acid) was investigated. The results of experiments in which hydrogen peroxide, catalase, or sodium azide were used singly or in combination suggest that the inhibition produced by the ascorbic acid oxidizing system is due, to a considerable extent, to the production of hydrogen peroxide. Dehydroascorbic acid was also found to inhibit the incorporation of S35-sulfate by cartilage slices. However, the gradual fall in pH which resulted from the addition of dehydroascorbic acid could account to a large extent for the inhibitory effect observed because the incorporation of S35-sulfate by cartilage slices decreases sharply as the pH is lowered. The incorporation of S35-sulfate by cartilage slices is inhibited also by increasing the concentration of phosphate.

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