The histochemical differentiation of various phosphatases in a population of osteoclasts by a simultaneous coupling method using different diazonium salts, with observations on the presence of inhibitors in stable diazonium salts

Synopsis The numerous osteoclasts in a giant cell tumour of bone were found to possess at least two distinct phosphatases capable of hydrolysing naphthol AS-TR phosphate. An acid phosphatase, with optimum activity about pH 4.7, could be demonstrated by simultaneous coupling with Fast Bordeaux OL or Red Violet LB, but not with Fast Red TR. The last-named salt, on the other hand, could be used for demonstrating a phosphatase with an optimum pH of activity about 7.3, showing some activity as an alkaline phosphatase at pH 8.3. This enzyme was markedly inhibited by zinc ions and could not be demonstrated by simultaneous coupling with diazonium salts stabilized with zinc chloride. The acid phosphatase was much less sensitive to zinc, but showed marked inhibition by aluminium, which had comparatively little effect on the other enzyme. Some discrepancies between the published formulae of stable diazonium salts and the substances found to be present in them are discussed.