EFFECTS OF INSULIN AND SOME VASOCONSTRICTORS ON THE SYNTHESIS AND RELEASE OF T-PA AND PAI-1 FROM CULTURED HUMAN UMBILICAL VEIN ENDOTHELIAL-CELLS

t-PA and PAI-1 are key components of the fibrinolytic system, The mech anisms regulating their synthesis and release are still unclear, Based upon clinical studies and cell culture studies, insulin has been sugg ested as one of the regulators of PAI-1, and some vasoconstrictors hav e been suggested as regulators of t-PA. We have investigated the effec t of some possible inducers of t-PA and PAI-1 synthesis and release in cultured human umbilical vein endothelial cells (HUVEC). HUVEC were g rown to confluence in 24-well tissue culture clusters and exposed to i nsulin, angiotensin II, endothelin-l, phorbol myristate acetate (PMA), lipopolysaccharide (LPS) or thrombin, The conditioned media were harv ested after a wide range of incubation times (from 15 min to 96 h), Th e media were analyzed for t-PA and PAI-1 antigen using ELISA methods. Medium harvested from cells stimulated with PMA contained significantl y higher levels of t-PA than the corresponding control cells (6 to 7-f old increase) and the medium harvested from cells stimulated with LPS showed a 1.5 to 3-fold increase in PAI-1, proving the reactivity of th e cells, Neither insulin, angiotensin II nor endothelin-l increased th e release of t-PA or PAI-1 compared to control cells at any time of ex position, Neither could we demonstrate any effect of insulin on the re lease of endothelin-1. However, taking the experimental limitations in to consideration, the present results do not preclude possible effects of these substances in vivo.