Endotoxin-induced secretion of an active plasminogen activator inhibitor from bovine pulmonary arterial and aortic endothelial cells

Abstract

Treatment of bovine pulmonary arterial and aortic endothelial cells for 24 h with 10-20 ng/ml endotoxin appeared to suppress urokinase secretion by over 90%. Immunodepletion of urokinase from conditioned medium revealed high levels of a fully active plasminogen activator inhibitor (PAI). In contrast, medium from aortic cells not treated with endotoxin expressed low levels of a latent PAI. The endotoxin-induced PAI from both cell types was not immunoprecipitated by incubation with IgG directed against the endothelial-type inhibitor, PAI-1, or antiserum directed against the placental-type inhibitor, PAI-2. Endotoxin-induced PAI was inactivated by 0.2-1.0 M of 2-mercaptoethanol, but unaffected by treatment with up to 500 microM of chloramine-T. We conclude that the exposure of bovine endothelial cells to endotoxin causes the secretion of a fully active PAI with properties different from those reported for PAI-1.