The influence of hyperestrogenism during in vitro fertilization on the fibrinolytic mechanism.

OBJECTIVE: To evaluate levels of various fibrinolytic factor antigens in women during ovulation induction using controlled ovarian hyperstimulation. METHODS: Plasma tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA), and the plasminogen activator inhibitors (PAI-1 and PAI-2) were evaluated and compared with plasma 17 beta-estradiol levels, ranging from 20 pg/mL to > 5,000 pg/mL during the course of treatment. Sixteen patients undergoing IVF were compared prior to (Controls) and following treatment with leuprolide acetate down-regulation followed by menopausal gonadotropin-CG ovulation induction for 14 days. RESULTS: A significant positive correlation was found between tPA and PAI-1 during treatment, while tPA and PAI-1 were negatively correlated with estradiol levels. Mean levels of tPA and PAI-1 significantly decreased as estradiol levels increased. CONCLUSIONS: As the plasminogen activator decreased with increasing estradiol levels, this suggests a potential for thrombosis. However, the major plasminogen activator inhibitor (PAI-1) also decreased; thus, the net clinical effect in terms of increased potential for thrombosis should be minimal. Furthermore, the levels of both tPA and uPA were still within normal ranges. The overall data from this study suggest that ovarian hyperstimulation with fertility-enhancing drugs does not enhance the potential for thrombosis even though there are elevated 17 beta-estradiol levels.

Production of various forms of plasminogen activator and plasminogen activator inhibitor by cultured mammary epithelial cells.

We examined amounts and types of plasminogen activator and plasminogen activator inhibitor produced by cultured bovine mammary epithelial cells. The MAC-T and two other mammary epithelial cell lines, MACT-UV1 and MACT-UV2 derived from the parental MAC-T cells by subcloning, were used as model systems. Cells were cultured in a medium free of serum and protein. Data showed that MACT-UV2 cells produced 6.2 and 17.2% more plasminogen activator than MACT-UV1 and parental MAC-T cells, respectively. Addition of amiloride, a specific urokinase-plasminogen activator inhibitor, dramatically decreased the activity in the culture medium of parental and subclonal lines, indicating that urokinase-plasminogen activator was present. Zymography revealed the presence of urokinase-plasminogen activator with an approximate molecular mass of 50,000 kDa in the culture medium of parental MAC-T cells. The culture medium of the subclonal lines contained urokinase-plasminogen activator and tissue-plasminogen activator with approximate molecular masses of 50,000 and 75,000 kDa, respectively. Complexes of both types of plasminogen activators with plasminogen activator-inhibitor-1 were detected in the culture medium of subclonal lines.

Induction of endothelial cell expression of the plasminogen activator inhibitor type 1 gene by thrombosis in vivo.

BACKGROUND: We have shown previously that products from activated platelets can augment synthesis of plasminogen activator inhibitor type 1 (PAI-1) in cultured endothelial and hepatoma (Hep G2) cells in vitro and increase plasma PAI-1 activity in vivo in rabbits. Accordingly, the effects of activation of platelets associated with thrombosis and thrombolysis in vivo on plasma PAI-1 activity and expression of the PAI-1 gene in endothelium, liver, and other organs were characterized. METHODS AND RESULTS: Endothelial injury giving rise to platelet-rich thrombi was induced with electrical stimulation in carotid arteries in rabbits. Clot lysis and recanalization were induced subsequently with intravenous tissue-type plasminogen activator (t-PA) and verified with Doppler flow probes. Plasma PAI-1 activity (mean +/- SD) increased from 6 +/- 2 arbitrary units (AU)/ml to 129 +/- 48 AU/ml (n = 15) within several hours after recanalization. When t-PA had failed to induce recanalization, the increase was much less (from 7 +/- 2 to 42 +/- 23 AU/ml, n = 11). To define mechanisms responsible for these changes, PAI-1 messenger RNA (mRNA) was evaluated by Northern blot analysis and localized in tissues by in situ hybridization. Strong and consistent induction of PAI-1 mRNA was evident in aorta, heart, and liver of animals subjected to thrombosis (twofold to threefold increases compared with values in controls), particularly in those in which thrombolysis had been induced (fourfold to sixfold). After thrombolysis, an intense, PAI-1 mRNA-specific signal was detected in endothelium of aorta, liver, and heart, with less intense signals in endothelium of lung, adrenals, and kidneys. CONCLUSIONS: The increases in plasma PAI-1 activity follow a preceding increase in endothelial cell expression of the PAI-1 gene as reflected by PAI-1 mRNA levels. Thus, increased synthesis of endothelial cell PAI-1 after thrombosis and thrombolysis may attenuate endogenous fibrinolysis early after coronary thrombolysis, thereby potentiating early, thrombotic reocclusion.