Artifacts in Mast Cell Metachromasia Produced by Hyaluronidase Preparations.

1) Commercially available hyaluronidase preparations appear to contain substances which are capable of preventing metachromatic staining of mast cells at pH 2 and 3 thus simulating enzymatic hydrolysis of stainable mucopolysaccharides. 2) Evidence suggests that staining is prevented by substances, perhaps proteins, which form a complex with mast cell mucopolysaccharides and prevent staining. It is possible that hyaluronidase itself may be one of the masking proteins. 3) The value of an inactivated enzyme control and use of salt solutions of hyaluronidase in histochemical studies is emphasized.