Connective tissue activation

A protein factor in human urine which has the ability to activate connective tissue cells has been identified and partially purified; it appears to be different from epidermal growth factor and IgG. This urinary connective tissue activating factor (CTAP‐U) is nondialyzable, labile to protease, stable to thiols, heat, and acid, and has an acidic isoelectric point. Purified preparations of CTAP‐U have biologic activities that cause human connective tissue cells to synthesize incremental amounts of 14 C‐hyaluronic acid, 35 S‐proteoglycans, and 3 H‐DNA in vitro. The cell spectrum responsive to this substance includes human synovial cells, human chondrocytes, and skin fibroblasts. CTAP‐U does not react with antisera to connective tissue activating peptide‐III or to antibodies against IgG or its Fc and Fab fragments. Furthermore, CTAP‐U does not cross‐react in a radioreceptor assay for insulin, basic somatomedin, or epidermal growth factor‐urogastrone. Utilizing standardized isolation conditions, CTAP‐U preparations with these properties have been isolated from the urine of 6 normal individuals.