This report describes the development and use of functional irnmunoradiometric assays that distinguish the activity of @-migrating endothelial-type plasminogen activator inhibitor (PAI-1) from that of placental-type plasminogen activator inhibitor (PAI-2). These assays are based upon the binding of PAL1 and PAL2 to immobilized single-chain tissue-type plasminogen activator (tPA) and to immobilized urokinase (UK), respectively. The extent of binding of each PA1 is quantified by incubating the PAI-PA complex first with rabbit antiserum specific for the individual PA1 and then with 1251-labeled goat antirabbit IgC. In control experiments, the assays were shown to be sensitive, dose-dependent over a wide range, and specific for each PAI. These assays were employed to establish the PA1 profile of a variety of human cells. Neither PAL1 nor PAI-2 could be detected in Bowes melanoma cells or in a renal adenocarcinoma cell line (ACHN), while the histiocytic lymphoma cell (U-937) produced only PAI-2. Five cell lines, including two that were previously shown to contain one or the other PA1 (e.g., umbilical vein endothelial cells and a fibrosarcoma cell line, HT-1080) in fact contained both PAls. The cells containing both PAls were studied in more detail. In each case, SDS treatment of CM was shown to enhance PAL1 activity (by converting the latent form of this inhibitor into its active form) and to destroy PAI-2 activity. Various compounds including interleukin 1, dexamethasone, and phorbol myristate acetate were found to selectively influence the cellular production of one PA1 without concomitantly affecting the production of the other, suggesting that the synthesis of these inhibitors is not coordinately regulated.
Plasminogen activators (PAS) play a n important role cytes (Kopitar et al., 198% and the histiocytic lymnot only during fibrinolysis but also in a variety of other phoma cell line, U-937 (Kruithof et al., 1986). It is physiological processes, including tissue repair, macro-primarily an inhibitor of urokinase (UK) and urokinasephage function, ovulation, embryo implantation, neo-like PA (UPA), whereas PAI-1 inhibits both uPA and vascularization, and malignant transformation (Astrup, tissue-type PA (tPA) Hekman and