Detection of hyaluronidase activity by a radiolabelled hyaluronan (HA) substrate assay. (a)Standard curve between the relative percentage of degraded HA molecules and the relative turbidity-reducing units (rTRUs) of hyaluronidase. (b) pH profile of the activity of proteins immunoprecipitated from chondrocyte-layer extracts (open squares), chondrocyte-conditioned media (open circles) and a commercial preparation of bovine testicular hyaluronidase (closed circles). Samples were analyzed in triplicate and activity was expressed as a percentage of maximal activity (= relative activity). A similar pH profile was obtained with specimens from synoviocyte-layer extracts and conditioned media.