SOME OBSERVATIONS ON THE INHIBITION OF THE ACTION OF HYALURONIDASE ON HYALURONIC ACID BY GENTISIC ACID AND ITS OXIDATION PRODUCTS

THE spreading factor, hyaluronidase, plays an important part in health and in disease. Its biological significance lies in its ability to depolymerise hyaluronic acid, which is present in many animal tissues and which appears to play a part in binding water in interstitial spaces. In synovial fluid, for example, hyaluronic acid holds cells together in a jelly-like matrix which serves as a lubricant and shock absorber in joints. Balance between hyaluronidase and hyaluronic acid is maintained by an enzyme inhibitor linked with the pseudoglobulin fraction of the serum. Hyaluronidase inhibition is also exercised by heparin, chondroitinsulphuric acid and gastric mucin. Certain rheumatic conditions are characterised by destruction or disorganisation of the synovial membranes, a process in which hyaluronidase is thought to play a part. Thus Guerral observed that intradermal injection of 1 per cent. hyaluronidase solution containing 1 per cent. of Evans Blue into patients suffering from rheumatic fever gave unique reactions characterised by enormous diffusion of the dye. Guerra interpreted these results as indicating increased hyaluronidase activity during the disease process. He made the further observation that administration of sodium salicylate decreased the severity of these reactions. He concluded that salicylates inhibit the “spreading effect” of hyaluronidase, an action to which he attributed, in part, the beneficial results of salicylate therapy in disorders of this character. Following these observations attempts were made by a number of workers to substantiate Guerra’s claims by in v i m studies. The method employed consisted in measurement of the degree of depolymerisation of a hyaluronic acid solution by a standardised enzyme preparation. The results obtained, however, showed clearly that salicylates had no effect upon the hyaluronidase-hyaluronic acid system except in relatively enormous concen t r a t i~ns .~~~~~J j The observations recorded by Guerra were, therefore, ascribed to the formation of salicylate metabolites, which were considered to be the true inhibitors of the action of hyaluronidase upon hyaluronic acid.