Hormonal regulation of the fibrinolytic components in the ovary

Expression of uPA, tPA, and PAI-1 in Calcified Aortic Valves

Purpose. Our physiopathological assumption is that u-PA, t-PA, and PAI-1 are released by calcified aortic valves and play a role in the calcification of these valves. Methods. Sixty-five calcified aortic valves were collected from patients suffering from aortic stenosis. Each valve was incubated for 24 hours in culture medium. The supernatants were used to measure u-PA, t-PA, and PAI-1 concentrations; the valve calcification was evaluated using biphotonic absorptiometry. Results. Aortic stenosis valves expressed normal plasminogen activators concentrations and overexpressed PAI-1 (u-PA, t-PA, and PAI-1 mean concentrations were, resp., 1.69 ng/mL ± 0.80, 2.76 ng/mL ± 1.33, and 53.27 ng/mL ± 36.39). There was no correlation between u-PA and PAI-1 (r = 0.3) but t-PA and PAI-1 were strongly correlated with each other (r = 0.6). Overexpression of PAI-1 was proportional to the calcium content of the AS valves. Conclusions. Our results demonstrate a consistent increase of PAI-1 proportional to the calcification. The overexpression of PAI-1 may be useful as a predictive indicator in patients with aortic stenosis.

Transition of pathophysiological significance of plasminogen activator inhibitor-From a chief player in antiinflammation, antifibrinolysis to that in the development of insulin resistance

In the early phase of research, plasminogen activator inhibitor (PAI) was regarded as a negative regulator of fibrinolytic system, but the later study clarified that the changes in PAI level is closely related to risk factors of various pathologic processes of the lifestyle-related diseases. It is accepted that PAI-1 is a risk factor of the cardiovascular event in lifestyle-related diseases by recent researches analyzing the detailed function of PAI-1. In this review paper, we described the transition of pathophysiological significance of PAI based on many research papers especially from ours, which clarified the mechanism on protein expression of PAI, especially PAI-1.

Lack of plasminogen does not alter the early inflammatory response following a tympanic membrane perforation: a study in plasminogen-deficient mice

CONCLUSIONS

The results of the present study show that the early inflammatory response in plasminogen (plg)-deficient mice is not altered compared to that in wild-type (wt) mice. Therefore the chronicity of the perforation in the long-term healing experiment cannot be explained by an impairment of the early inflammatory response, but rather by an impairment in activation of the inflammatory cells. These findings give further insight into the mechanisms resulting in a clinically seen chronic tympanic membrane (TM) perforation and thus possible therapeutic strategies to replace today's conventional surgical treatment of these perforations.

OBJECTIVES

Plg has been shown to play an essential role in the healing of TM perforations. In plg-deficient mice a completely arrested healing reaction was seen, resulting in a chronic TM perforation. The mechanisms involved seem to be an abundant neutrophil recruitment, an accumulation of macrophages, an arrested keratinocyte migration, and a massive deposition of fibrin along the TM tissue. However, the exact functional role of plg in the early inflammatory response during healing of TM perforation remains unclear. This study aimed to evaluate the early inflammatory response, mainly the occurrence of macrophages and neutrophils, during the first 48 h following a perforation in the pars tensa (PT) of the TM, in mice lacking the plasminogen gene compared to the corresponding response in wt mice.

MATERIALS AND METHODS

The TMs were perforated in 45 plg-deficient and 39 wt mice. Otomicroscopic evaluation was performed at 3, 6, 9, 12, 18, 24, and 48 h after the perforation was made. Mice were harvested at all time points and prepared for morphology including immunohistochemistry (IHC). IHC was performed with antibodies targeting macrophages, neutrophils, T and B cells, cytokeratin, and fibrin(ogen). Morphometry was performed regarding the volume percentage of TM tissue occupied by the different inflammatory cells.

RESULTS

Perforation of the TM resulted in early otomicroscopic changes of the pars flaccida (PF) in both genotypes. Infiltration of inflammatory cells to PF and the presence of edema occurred as early as 6 h after the perforation was made, in both plg-deficient and wt mice. Morphometry did not reveal any significant differences between the genotypes concerning the occurrence of inflammatory cells. In contrast to the PF, the PT showed only sparse reactions during the experimental period. Furthermore, the migration pattern of keratinocytes did not differ between the genotypes throughout the experimental period.

NKT cell-derived urokinase-type plasminogen activator promotes peripheral tolerance associated with eye

In a model of peripheral tolerance called anterior chamber-associated immune deviation (ACAID), the differentiation of the T regulatory cells depends on NKT cells and occurs in the spleen. In this study, we show that NKT cells that express the invariant (i) TCR and are the CD1d-reactive NKT cells (required for development of peripheral tolerance) actually produced urokinase-type plasminogen activator (uPA) during tolerance induction. The RT-PCR and in vitro plasmin assay showed that splenic iNKT cells derived uPA-converted plasminogen to plasmin. Moreover, uPA was required for tolerance induction because uPA knockout (KO) mice did not develop peripheral tolerance or develop CD8(+) T regulatory cells after Ag inoculation into the anterior chamber. In contrast, other aspects of ACAID-induced tolerance, including recruitment of iNKT cells to the spleen and production of IL-10 by iNKT cells, were unchanged in uPA-deficient mice. The adoptive transfer of splenic NKT cells from wild-type mice restored ACAID in Jalpha18 KO mice (iNKT cell deficient), but NKT cells from uPA KO mice did not. We postulate that the mechanism of action of uPA is through its binding to the uPAR receptor, and enzymatic cleavage of plasminogen to plasmin, which in turn activates latent TGFbeta. In conclusion, uPA derived from iNKT cells is required to induce peripheral tolerance via the eye.

Extracellular matrix in ovarian follicular development and disease

The ovarian follicle contains several different cell types and separate compartments and undergoes substantial development during its growth and maturation. Extracellular matrix (ECM) could be expected to play a major role in these processes. Most research on ECM in follicles has focused on the follicular basal lamina and its changing composition during folliculogenesis and on the specialised matrix formed at ovulation by the cumulus cells surrounding the oocyte and the zona pellucida. We review these aspects. Few naturally occurring gene mutations have identified unique roles for ECM molecules in follicular function. Presumably, any mutations leading to reduced fertility are eliminated quickly by natural selection and, when mutations are not eliminated, considerable redundancy occurs to ensure successful reproduction. In mice, in which the genome can be easily manipulated, the modification of matrix components associated with cumulus and oocytes has often resulted in partial infertility, suggesting redundancy. We provide an update of basal lamina components focusing on newer discoveries. In addition, we review matrix associated with the occyte and cumulus cells (excluding the zona pellucida) and other components of ECM. Where possible, we examine evidence for the role of the ECM in follicular development and diseases.

The plasminogen activator/plasmin system is essential for development of the joint inflammatory phase of collagen type II-induced arthritis

The plasminogen activator (PA) system has been proposed to have important roles in rheumatoid arthritis. Here we have used the autoimmune collagen type II (CII)-induced arthritis (CIA) model and mice deficient for urokinase-type PA (uPA) or plasminogen to investigate the role of the PA system for development of arthritis. Our data revealed that uPA-deficient mice have a lower severity and incidence of CIA than wild-type mice. Furthermore, although >80% of wild-type control mice developed CIA, we found that none of the 50 plasminogen-deficient littermates that were tested developed CIA within a 40-day period. Antibody generation after CII immunization as well as the binding of labeled anti-CII antibodies to the surface of cartilage were similar in wild-type and plasminogen-deficient mice. No sign of inflammation was seen when plasminogen-deficient mice were injected with a mixture of monoclonal antibodies against CII. However, after daily injections of human plasminogen, these mice developed arthritis within 5 days. Our finding that infiltration of inflammatory cells into the synovial joints was impaired in plasminogen-deficient mice suggests that uPA and plasminogen are important mediators of joint inflammation. Active plasmin is therefore essential for the induction of pathological inflammatory joint destruction in CIA.

Contrasting roles of plasminogen deficiency in different rheumatoid arthritis models

OBJECTIVE

To investigate the contrasting roles of plasminogen deficiency between models of collagen-induced arthritis (CIA) and antigen-induced arthritis (AIA).

METHODS

We developed a new animal model of arthritis, which we have called local injection-induced arthritis (LIA). In this model, we replaced methylated bovine serum albumin, which is normally used as an immunogen and is injected intraarticularly into the knee joint, with type II collagen (CII) to induce AIA. The severity of CIA, LIA, and AIA in wild-type and plasminogen-deficient mice was evaluated by clinical scoring or histologic grading. Necrosis was determined by histology and immunohistochemistry.

RESULTS

After CII immunization alone, wild-type mice developed arthritis in most of the paws as well as in the knee joints, whereas plasminogen-deficient mice were totally resistant to the disease. Local knee injections of CII or saline slightly enhanced the severity of the knee arthritis in wild-type mice during a 60-day experimental period. Unexpectedly, the plasminogen-deficient mice also developed arthritis in joints that were injected with CII or saline. However, the arthritis was milder than that in their wild-type littermates. Sustained tissue necrosis was found only in the plasminogen-deficient mice after the local injection.

CONCLUSION

Our data show that both the antigen and the joint trauma caused by the local injection are critical to explaining the contrasting roles of plasminogen deficiency in CIA and AIA. This further indicates that CIA and AIA have distinct pathogenic mechanisms. The data also suggest that plasmin may be required for the induction of these arthritis models that are critically dependent on complement activation.

Urokinase plasminogen activator (uPA) and its receptor (uPAR) in gestational tissues; Measurements and clinical implications

BACKGROUND

Urokinase plasminogen activator (uPA) and urokinase plasminogen activator receptor (uPAR) are central molecules for uPA/uPAR/plasmin-dependent proteolysis, which is thought to play a significant role in the development of pregnancy, as well as its many complications.

OBJECTIVE

To measure the levels of uPA and uPAR in the placenta and myometrium, as well as in the foetal membranes and amniotic fluid.

STUDY DESIGN

The study group consisted of 35 women with normal course of pregnancy, but with complications arising during delivery, which led to Caesarean section. Samples of placenta, myometrium, foetal membranes, amniotic fluid and blood were obtained at the time of operation. Tissue extracts were prepared. Measurements were made by the ELISA method.

RESULTS

uPA and uPAR concentration in gestational tissues, including amniotic fluid, is 100-200 times higher than in plasma. Among tissues, the highest uPA level was found in placenta ( 1.32 +/- 0.48 ng/mg of protein), and the highest uPAR level in foetal membranes (3.33 +/- 1.20 ng/mg of protein).

CONCLUSIONS

uPA and uPAR are present in all gestational tissues, in some in relatively high concentrations. Our results support the modern clinical hypothesis that fibrinolytic system can participate in mechanisms of such obstetric complications as pre-term pre-mature rupture of foetal membranes and placental abruption.

Hyperfibrinogenemia in rats treated with meloxicam

Fibrinogen secretion is mediated by prostaglandin biosynthesis and is considered a risk factor for cardiovascular disease. Since meloxicam produces inhibition of prostaglandin biosynthesis it may help to normalize hyperfibrinogenemia. We investigated the pharmacological effect of meloxicam on fibrinogen levels and the possible regression of histopathological lesions of thoracic aorta. Rats were subjected to multiple injuries (MI) in the form of laparotomies (Lx) during a 30 day period (1/week). Meloxicam 0.065 mg/kg/day (per rat) was administered orally immediately after the third Lx in multiple injury animals during a ten day period. Blood was obtained 72 hours after the last injury in all groups. Fibrinogen was measured by spectrophotometry and the values were expressed in mg/dL. A statistically significant increment of fibrinogen was observed when comparing uninjured animals (control) (208.7+/-6.0) with the multiple injury group (336.6+/-7.5) (P<0.001). Fibrinogen decreased to the control value in the meloxicam group (198+/-8.7). Histopathological lesions were similar in the MI and meloxicam groups, showing endothelial denudation and intima enlargement from the thoracic aorta in 96% of the slices studied. The decrease in fibrinogen in the meloxicam group would be due to cyclooxygenase-2 (Cox-2) selective inhibition, even though the histopathological lesions did not regress.

Matrix remodeling in the ovary: regulation and functional role of the plasminogen activator and matrix metalloproteinase systems

In each reproductive cycle, extensive tissue remodeling takes place in the ovary during follicular development, ovulation, formation and regression of corpus luteum (CL) and follicular atresia. Several lines of indirect evidence suggest that these changes are mediated, in part, by proteases belonging to the plasminogen activator (PA) and the matrix metalloproteinase (MMP) systems. These two enzyme systems include both proteinases and associated inhibitors, that are thought to act in concert via a cascade of proteolytic events, the end result of which is the generation of a broad spectrum proteolytic activity, that can mediate physiological tissue remodeling throughout the body. The current review highlights the key features of these two enzyme systems and focuses on their regulation and functional role during the dynamic remodeling processes that takes place in the ovary during each reproductive cycle.

Regulation and localization of matrix metalloproteinases and tissue inhibitors of metalloproteinases in the mouse ovary during gonadotropin-induced ovulation

At the time of ovulation, proteolytic degradation of the follicular wall is required to release the mature oocyte. Extracellular proteases, such as serine proteases and matrix metalloproteinases (MMPs), are thought to play important roles in this process. In this study we have examined the regulation of 11 MMPs and 3 tissue inhibitors of metalloproteinases (TIMPs) during gonadotropin-induced ovulation in the mouse. Northern blot hybridization showed that messenger RNA for several MMPs and TIMPs, including gelatinase A, MT1-MMP, stromelysin-3, MMP-19, TIMP-1, TIMP-2, and TIMP-3, were present at detectable levels in the mouse ovary. In addition, ovarian extracts contained gelatinolytic activities corresponding to the inactive proforms of gelatinase A and gelatinase B. Most of the MMPs and TIMPs were expressed at a constitutive level throughout the periovulatory period. However, MMP-19 and TIMP-1 revealed a different expression pattern; they were both induced 5-10 times by hCG and reached their maximum levels at 12 h after hCG treatment, corresponding to the time of ovulation. At this time point, MMP-19 and TIMP-1 messenger RNA were localized to the granulosa and thecal-interstitial cells of large preovulatory and ovulating follicles. This temporal and spatial regulation pattern suggests that MMP-19 might be involved in the tissue degradation that occurs during follicular rupture and that TIMP-1 could have a role in terminating MMP activity after ovulation.

Determination of the Complex between Urokinase and Its Type-1 Inhibitor in Plasma from Healthy Donors and Breast Cancer Patients

Background: The complex between urokinase (uPA) and its type-1 inhibitor (PAI-1) is formed exclusively from the active forms of these components; thus, the complex concentration in a biological sample may reflect the ongoing degree of plasminogen activation. Our aim was to establish an ELISA for specific quantification of the uPA:PAI-1 complex in plasma of healthy donors and breast cancer patients.

Methods: A kinetic sandwich format immunoassay was developed, validated, and applied to plasma from 19 advanced-stage breast cancer patients, 39 age-matched healthy women, and 31 men.

Results: The assay detection limit was &lt;2 ng/L, and the detection of complex in plasma was validated using immunoabsorption, competition, and recovery tests. Eighteen cancer patients had a measurable complex concentration (median, 68 ng/L; range, &lt;16 to 8700 ng/L), whereas for healthy females and males the median signal values were below the detection limit (median, &lt;16 ng/L; range, &lt;16 to 200 ng/L; P &lt;0.0001). For patient plasma, a comparison with total uPA and PAI-1 showed that the complex represented a variable, minor fraction of the uPA and PAI-1 concentrations of each sample.

Conclusion: The reported ELISA enables detection of the uPA:PAI-1 complex in blood and, therefore, the evaluation of the complex as a prognostic marker in cancer.

Temporal expression of urokinase type plasminogen activator, tissue type plasminogen activator, plasminogen activator inhibitor type 1 in rhesus monkey corpus luteum during the luteal maintenance and regression

Proteolytic activity generated by the plasminogen activator (PA) system has been associated with many biological processes. Using a pregnant mare serum gonadotropin (PMSG)/human chorionic gonadotropin (hCG)-induced rhesus monkey corpus luteum (CL) model, we have studied how urokinase-type plasminogen activator (uPA), tissue-type plasminogen activator (tPA), and plasminogen activator inhibitor type 1 (PAI-1), are temporally expressed in CL of rhesus monkey at the luteotropic and luteolytic periods. Slot blot analysis and in situ hybridization were performed to analyze the expression and distribution of uPA and PAI-1 messenger RNA (mRNA). Fibrin overlay was used to detect uPA and tPA activities. We found that uPA is the dominating PA in luteotropic CL in the monkey. Abundant expression of PAI-1 mRNA was detected. The highest expression of uPA and PAI-1 mRNA was observed at the luteotropic period, while their expression decreased approximately 50% at early luteal regression defined by considerably decreased serum progesterone levels, and remained at very low levels at the late stage of luteal regression. We also observed an increased tPA activity at the time of luteal regression. Moreover, the exogenous tPA could inhibit the progesterone production in cultured luteal cells from 13-day-old monkey CL. We also used LH receptor mRNA expression as a mark for the luteal phases. A highly expressed, evenly distributed LH receptor mRNA was detected in CL during the luteotropic phase, while its expression decreased at day 13 coinciding with the reduction of progesterone production. We conclude that proteolysis mediated by uPA and regulated by PAI-1 may play a role in the luteal maintenance, while tPA may participate in the luteal regression in the rhesus monkey.

Characterisation of the rat tissue-type plasminogen activator gene promoter -- identification of a TAAT-containing promoter element

Tissue-type plasminogen activator (tPA) activates plasminogen to the active protease plasmin and is implicated in many biological processes that require extracellular proteolysis. In rat ovarian cells, gonadotropins induce the tPA gene by a cAMP-dependent pathway and this induction correlates with the time of follicular rupture. We have previously identified several promoter elements within the first 621 bp of the rat tPA promoter that are important for constitutive and cAMP-induced expression of the gene, including a cAMP responsive element (CRE), a nuclear factor 1 (NF1) element, a SP1-binding site and a G+C-rich box. In this report we have extended our study by analysing promoter constructs, ranging in size from 7.7 kb to 135 bp fused to the luciferase reporter gene. Transient transfection analysis of rat granulosa cells and human 293 cells, reveal that the proximal 268 bp of the promoter is enough to confer high basal and cAMP-induced expression of the gene. At position -162 to -172, between the previously identified CRE and NF1 sites, a novel TAAT-containing promoter element was identified. Mutational inactivation of the TAAT motif indicates that this element is important for both constitutive and cAMP-induced expression of the gene, and for the binding of a presumably novel nuclear factor that we have termed tPA promoter factor-1 (tPF-1).

Studies of mice lacking plasminogen activator gene function suggest that plasmin production prior to ovulation exceeds the amount needed for optimal ovulation efficiency

Many studies suggest that the plasminogen activator (PA) system plays a role in the proteolytic degradation of the follicle wall at the time of ovulation. Consistently, the ovulation efficiency is reduced by 26% in mice where both physiological PA genes have been inactivated. To reveal the mechanism behind reduced ovulation efficiency in PA-deficient mice and its effect on ovarian proteolysis. we have studied the regulation of plasmin activity in the ovaries of 25-day-old wild-type mice and mice with deficient PA gene function during gonadotropin-induced ovulation. In wild-type mice the plasmin activity was low in ovarian extracts from mice treated with pregnant mare's serum gonadotropin. However, this activity was increased between 2-8 h after an ovulatory dose of human choriogonadotropins. In mice lacking either tissue-type PA (tPA) or PA inhibitor type 1 (PAI-1) the plasmin activity levels prior to ovulation were similar to wild-type mice, while extracts prepared from urokinase-type PA (uPA) deficient mice had 10% or less of the plasmin activity. This indicates that most of the plasmin activity in the mouse ovary is generated by uPA. In addition, as the ovulation efficiency is impaired in tPA/uPA-deficient mice but appears normal in uPA-deficient mice, our data indicates that the amount of plasmin generated by PAs prior to ovulation in wild-type mice greatly exceeds the amount required for efficient ovulation.

Fibronectin concentrations correlate with ovarian follicular size and estradiol values in equine follicular fluid

The amounts of total protein, albumin, fibronectin, alpha 2-macroglobulin (alpha 2-M), immunoglobulin G, ceruloplasmin and antithrombin were determined in fluids collected from 53 preovulatory equine follicles and compared with the contents of estradiol-17 beta, progesterone and androstenedione, with follicle size and the amounts of the equivalent proteins in normal equine plasma. The concentration of fibronectin and the fibronectin/albumin ratios increased significantly with follicle size and with follicular estradiol levels. The alpha 2-M levels and alpha 2-M/albumin ratios correlated with follicle size but not with hormone content. Both fibronectin and alpha 2-M were present in lower amounts in follicular fluid compared with plasma while the other proteins were present in similar amounts. Among the proteins evaluated, there was a positive correlation between the amount of the protein in the follicular fluid and the molecular weight of the protein.

Tissue plasminogen activator and plasminogen activator inhibitors of type 1 and type 2 in the plasma of parturient women

Changes in the fibrinolytic system of parturient women have so far been only partially documented. Our main questions were whether and how the concentration of tissue plasminogen activator (tPA) and plasminogen activator inhibitors of type 1 (PAI-1) and type 2 (PAI-2) change in the plasma throughout normal labor. The study group consisted of 38 women with normal pregnancy, delivering at term. The concentration of antigens tPA, PAI-1 and PAI-2 in plasma was tested by enzyme-linked immuno-sorbent assay method, and the activity of PAI-1 by plasmin method. Results were analysed statistically. During labor the level of tPA antigen increases over two times: from 9.3 +/- 4.3 ng/ml before labor, to 23.3 +/- 9.6 ng/ml in the second stage of labor. Changes of PAI-1 antigen as well as its activity though noticeable, were not statistically significant. PAI-2 antigen level increased significantly in the third stage (146.3 +/- 58.7 ng/ml before labor, and 212.2 +/- 75.0 ng/ml after placenta expulsion). In summary the more significant change in the fibrinolytic system during labor is an increase of the level of tPA and PAI-2 antigens, but their peaks appear in different stages of labor. The predominance of PAIs over tPA is maintained throughout the whole labor, though on a lower level as can be inferred from the tPA/PAIs ratio.

Ovulation efficiency is reduced in mice that lack plasminogen activator gene function: functional redundancy among physiological plasminogen activators

Several lines of indirect evidence suggest that plasminogen activation plays a crucial role in degradation of the follicular wall during ovulation. However, single-deficient mice lacking tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA), or PA inhibitor type 1(PAI-1) gene function were recently found to have normal reproduction, although mice with a combined deficiency of tPA and uPA were significantly less fertile. To investigate whether the reduced fertility of mice lacking PA gene function is due to a reduced ovulation mechanism, we have determined the ovulation efficiency in 25-day-old mice during gonadotropin-induced ovulation. Our results reveal that ovulation efficiency is normal in mice with a single deficiency of tPA or uPA but reduced by 26% in mice lacking both physiological PAs. This result suggests that plasminogen activation plays a role in ovulatory response, although neither tPA nor uPA individually or in combination is obligatory for ovulation. The loss of an individual PA seems to be functionally complemented by the remaining PA but this compensation does not appear to involve any compensatory up-regulation. Our data imply that a functionally redundant mechanism for plasmin formation operates during gonadotropin-induced ovulation and that PAs together with other proteases generate the proteolytic activity required for follicular wall degradation.

Hemostatic profile of bovine ovarian follicular fluid

The hemostatic profile of bovine ovarian follicular fluid was evaluated and the levels of procoagulant, fibrinolytic, and inhibitory activity compared with plasma. The results of the prothrombin time assay and the presence of fibrinogen along with factor VII and factor X activity indicate that bovine follicular fluid possesses components of the "extrinsic" or "tissue factor" coagulation system. The absence of factor VIII:C activity, along with the extremely low levels of factors IX and XI, indicates that there is not a functional "intrinsic" coagulation pathway. The fluid derived from large follicles exhibited increased levels of factors VII and X activity and a shorter prothrombin time compared with fluid obtained from the less mature small follicles. Similar alterations in the levels of the inhibitory proteins antithrombin III and alpha 2-macroglobulin were observed. Overall the amount of antithrombin III was similar to that in plasma, the levels of fibrinogen and factor X were approximately 2-fold lower, and the levels of factor VII and factor X were approximately 10-fold lower than in plasma. The fibrinolytic activity in follicular fluid was greater than the procoagulant or inhibitory activity. Plasminogen activator activity was 5-fold higher, while both plasminogen and antiplasmin values were similar to plasma levels.

The hemostatic profile of equine ovarian follicular fluid

The coagulation factors VII and X and fibrinogen were detected in equine ovarian follicular fluid. The amounts of fibrinogen and factor X were approximately 40 percent of that found in normal equine plasma while the level of factor VII was lower, at approximately 14 percent. The addition of human recombinant tissue factor caused fibrin formation in the follicular fluid. The thrombin generating activity appears to be confined to the tissue factor pathway since no activity associated with factors VIII:C, IX or IX was detected. Fibrinolytic activity, at higher levels than that found in plasma, was detected in all follicular fluid samples. It is proposed that the hemostatic mechanism may be modulated in follicular fluid in a manner analogous to that in plasma since inhibitory proteins including AT-III and antiplasmin were present in the follicular fluid samples at relatively constant levels that approached those found in normal equine plasma.

Fluorescence studies on plasminogen activator inhibitor 1: reactive centre cysteine mutants remain active after fluorophore attachment

To investigate structural-functional aspects of plasminogen activator inhibitor 1 (PAI-1) we have taken advantage of the lack of cysteines in the PAI-1 molecule and replaced Ser344 (P3) and Asn329 (P18) with cysteine residues, thereby creating unique attachment sites for extrinsic fluorescent probes. After expression in E. coli and purification to homogeneity, both of the mutant proteins were found to have similar biochemical characteristics as wild type PAI-1 (wtPAI-1). Following labelling with 4-chloro-7-nitrobenzofurazan (NBD) and 2-(4'-iodoacetamido-anilino)naphtalene-6-sulfonic acid (IAANS) the mutant inhibitors showed similar inhibitory activities and heat stability as wtPAI-1. The purified complex between uPA and NBD-labelled P3cys mutant was found to be extremely stable, suggesting that no slow cleavage or reversible reaction occurs in complexes that have been properly formed. The rate of labelling of both mutants was decreased when the mutants were in the latent form indicating that these cysteine residues may be less accessible in the latent configuration. The PAI-1 mutants labelled with both NBD and IAANS could convert from the active to the latent form, but P3cys labelled with the larger IAANS chromophore showed a two fold decrease in the rate of conversion to latency, suggesting that a large chromophore in the P3 position may interfere with the active to latent conversion. The fluorescence spectra of the two NBD labelled mutants were similar, but the intensity was three times higher for the P3cys mutant than for P18cys. No significant spectral changes could be seen when the P3cys mutant was transferred to latency. In contrast, the P18cys mutant showed a major change in the excitation spectra characteristic of migration of the NBD chromophore from a thiol to an amine. Complex formation with uPA had no effect on the fluorescence spectrum of P18cys-NBD while the spectrum of P3cys-NBD revealed changes consistent with a restriction of the mobility of NBD probe in the uPA-PAI-1 complex.