Determination of antipyrine sulphoconjugates in isolated cultured rat hepatocytes.

1. An analytical method for the simultaneous determination of three major metabolites of antipyrine, namely, 3-hydroxymethylantipyrine (phase I), 4-hydroxyantipyrine sulphoconjugate (phase II) and norantipyrine sulphoconjugate (phase II) in cultured rat hepatocytes has been developed and applied to the study of induction or inhibition of these metabolic pathways following pretreatment of rats with several inducers or inhibitors. 2.

Importance of plasminogen activator inhibitor type 1 (PAI-1) for preventing single chain urokinase plasminogen activator (scu-PA) conversion into two chain urokinase plasminogen activator (tcu-PA) in plasma in vitro.

We have studied the effects of PAI-1 on the conversion of scu-PA into tcu-PA in vitro in plasma containing or not a 125I-fibrin clot by determining tcu-PA activity on S2444. Two preparations of PAI-1 have been used, a fraction of medium conditioned with the monkey Vero cells (Vero-Prep), the antiurokinase activity of which is inhibited at 83% by anti PAI-1 IgG, or purified human PAI-1 from HT 1080 fibrosarcoma cells. Scu-PA purified from human kidney cells has been treated with diisopropylfluorophosphate before use.

Tumor necrosis factor (TNF) stimulates plasminogen activator inhibitor (PAI) production by endothelial cells and decreases blood fibrinolytic activity in the rat.

The effect of human recombinant tumor necrosis factor (TNF) was studied in vitro on human endothelial cells. TNF (1-1000 pg/ml) induced a dose-dependent increase in PAI level in the supernatant from 6 to 25 U/ml as estimated against urokinase. This effect was time-dependent.

Effect of polymyxin B and colimycin on induction of plasminogen antiactivator by lipopolysaccharide in human endothelial cell culture.

The effect of lipopolysaccharide (LPS) on the production of fibrinolytic inhibitor by human endothelial cells was determined because results of previous experiments have shown us that it is possible to stimulate this synthesis with muramyl dipeptide. Treatment of these cells with LPS resulted in a marked enhancement of fibrinolytic inhibitor, as estimated in a urokinase-induced fibrinolysis assay. A dose-response curve was obtained for LPS concentrations ranging from 10 to 1,000 ng/ml, thus demonstrating the great sensitivity of these cells.

Stimulation of human endothelial cells by synthetic muramyl peptides: production of colony-stimulating activity (CSA).

The in vivo induction of colony-stimulating activity (CSA) by well-defined immunomodulatory synthetic muramyl peptides has been demonstrated recently in mice. In the present study, we tested the capacities of three muramyl peptides to induce CSA production in human endothelial cell (HEC) cultures. Two adjuvant-active peptides (MDP and Murabutide) induced CSA in the supernatant of cultured endothelial cells, whereas an adjuvant-inactive compound had no effect.