Identification of bistable populations of Porphyromonas gingivalis that differ in epithelial cell invasion.

Bistable populations of bacteria give rise to two or more subtypes that exhibit different phenotypes. We have explored whether the periodontal pathogen Porphyromonas gingivalis exhibits bistable invasive phenotypes. Using a modified cell invasion assay, we show for the first time that there are two distinct subtypes within a population of P. gingivalis strains NCTC 11834 and W50 that display differences in their ability to invade oral epithelial cells. The highly invasive subtype invades cells at 10-30-fold higher levels than the poorly invasive subtype and remains highly invasive for approximately 12-16 generations. Analysis of the gingipain activity of these subtypes revealed that the highly invasive type had reduced cell-associated arginine-specific protease activity. The role of Arg-gingipain activity in invasion was verified by enhancement of invasion by rgpAB mutations and by inclusion of an Arg-gingipain inhibitor in invasion assays using wild-type bacteria. In addition, a population of ΔrgpAB bacteria did not contain a hyperinvasive subtype. Screening of the protease activity of wild-type populations of both strains identified high and low protease subtypes which also showed a corresponding reduction or enhancement, respectively, of invasive capabilities. Microarray analysis of these bistable populations revealed a putative signature set of genes that includes oxidative stress resistance and iron transport genes, and which might be critical to invasion of or survival within epithelial cells.

Expression of the alphavbeta6 integrin promotes migration and invasion in squamous carcinoma cells.

The integrin alphavbeta6 is a fibronectin receptor whose expression is not detectable on normal oral epithelium but is increased significantly in healing and in oral epithelial dysplasia and oral squamous cell carcinoma, suggesting it may promote changes associated with tumor development. To study whether alphavbeta6 may drive invasive behavior we have used transfection and retroviral infection to create a panel of epithelial cell lines expressing various levels of alphavbeta6. We report that increased expression of alphavbeta6 in malignant keratinocytes promotes invasion and leads to an increased capacity for migration towards fibronectin. alphavbeta6 expression may have a significant role in contributing to the malignant behavior of epithelial cells.

Changes in pericardial morphology and fibrinolytic activity during cardiopulmonary bypass.

The presence of pericardial adhesions at resternotomy not only increases the operation time but also increases the risk of serious damage to the heart, great vessels, and extracardiac grafts. The reported prevalence of damage is 2% to 6%. The fibrinolytic activity of pericardial tissue may be a crucial factor in determining the extent of adhesion formation following primary operation. Ten patients undergoing cardiac operations were studied to assess the plasminogen activating activity of homogenates of pericardial tissue samples. Samples were taken at three times during the operation and the plasminogen activating activity was measured by means of a standard fibrin plate technique. Tissue-type plasminogen activator, urokinase-type plasminogen activator, plasminogen activator inhibitor-1, and plasminogen activator inhibitor-2 were also measured by means of enzyme-linked immunosorbent assays. Compared with its initial levels (median 2.06 IU/cm2, range 1.28 to 6.48 IU/cm2), the plasminogen activating activity of pericardial biopsy tissue was significantly reduced at 75 minutes (median 0.64 IU/cm2, range 0.12 to 2.44 IU/cm2, p < 0.01) and at 135 minutes (median 1.45 IU/cm2, range 0.12 to 4.39 IU/cm2, p < 0.05). The major plasminogen activator present was tissue-type plasminogen activator. Compared with its initial levels (median 2.34 ng/ml, range 1.03 to 6.42 ng/ml), subsequent tissue-type plasminogen activator values were also significantly reduced at 75 minutes (median 0.83 ng/ml, range 0.75 to 5.13 ng/ml, p < 0.005) and at 135 minutes (median 1.24 ng/ml, range 0.75 to 6.67 ng/ml, p < 0.05). Low levels of urokinase-type plasminogen activator were found in 5 of 10 patients. However, neither plasminogen activator inhibitor-1 nor plasminogen activator inhibitor-2 was detected. Examination with a light microscope showed both increasing pericardial mesothelial damage and increasing features of acute inflammatory changes with time. This study shows that plasminogen activating activity is present in pericardial tissue and that tissue-type plasminogen activator is the major plasminogen activator. The observed inflammatory changes and concomitant damage to the pericardial mesothelium, and the significant reductions in pericardial tissue-type plasminogen activator and plasminogen activating activity seen during cardiac operations, may be important factors contributing to the early development of pericardial adhesions.

Perioperative histologic and ultrastructural changes in the pericardium and adhesions.

The presence of pericardial adhesions prolongs the operation time and increases the risk of serious damage to the heart and other major vascular structures during resternotomy. The reported incidence of such damage is 2% to 6%. Pericardial mesothelial cells exhibit fibrinolytic activity, and therefore have an actual or potential role in the breakdown of the fibrinous adhesions that serve as the initial scaffolding for the firm collagenous adhesions seen at reoperation. Ten patients undergoing primary cardiac procedures were studied to assess the morphologic changes that take place within the pericardium and to relate these to accompanying changes in the pericardial plasminogen activating activity. Samples were taken at 0, 75, and 135 minutes after pericardiotomy. Compared with samples obtained at the time of pericardiotomy, those taken at 75 and 135 minutes demonstrated a significant progression in the mesothelial cell damage (p < 0.01), together with increasing evidence of pericardial inflammation (p < 0.01). The findings from electron microscope studies confirmed and supplemented these findings. Furthermore, compared with its initial levels (median, 2.06 IU/cm2; range, 1.28 to 6.48 IU/cm2), the plasminogen activating activity of pericardial biopsy specimens was significantly reduced at 75 minutes (median, 0.64 IU/cm2; range, 0.12 to 2.44 IU/cm2; P < 0.05), with some recovery at 135 minutes (median, 1.45 IU/cm2; range, 0.12 to 4.39 IU/cm2; p = 0.059). This study has revealed that, during cardiac procedures, the pericardium undergoes inflammatory changes with concomitant damage to its mesothelium, together with a reduction in the pericardial mesothelial fibrinolytic potential.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental adhesion prophylaxis with recombinant tissue plasminogen activator.

The deposition of fibrin in the peritoneal cavity leads to fibrous adhesion formation. Recombinant tissue plasminogen activator (rtPA), delivered locally, was investigated as a method of preventing adhesion formation. Six standardised areas of peritoneal ischaemia were formed in each of 36 male Wistar rats randomised to three intraperitoneal treatments: (A) no treatment control; (B) carboxymethylcellulose gel; (C) rtPA-carboxymethylcellulose gel combination. At 1 week all animals underwent relaparotomy and the number of ischaemic sites with an adhesion counted by an independent observer. rtPA-treated animals formed fewer adhesions compared with gel alone or controls (median number of adhesions 1.5 versus 2.5 versus 5, P < 0.001, ANOVA). Intraperitoneal rtPA in a slow-release formulation is able to reduce adhesion formation significantly in an animal model and may prove to have clinical benefit.

Endothelin-1 stimulates oral fibroblasts to promote oral cancer invasion.

AIMS: The aims of this study were to examine the role of endothelin-1 (ET-1), a pleiotropic peptide found at elevated levels in a number of malignancies and which has been shown to influence oral cancer cell behaviour via paracrine signalling pathways, on the phenotype of oral fibroblasts. MAIN METHODS: The effect of ET-1 on proliferation and migration of human primary oral fibroblasts was assessed using MTS and scratch assays, respectively. The ability of ET-1 to affect fibroblast contractility was analysed using type-I collagen gels. Changes in gene expression in oral fibroblasts exposed to ET-1 were examined using quantitative PCR. The invasiveness of oral cancer cells in the presence of conditioned media collected from ET-1 treated fibroblasts was determined using 2D Matrigel assays. KEY FINDINGS: Here we provide evidence that ET-1 increases the migration of oral fibroblasts and induces a more contractile phenotype which is not associated with changes in gene expression indicative of myofibroblast transdifferentiation. In addition we provide evidence that conditioned medium of ET-1-stimulated oral fibroblasts promotes invasion of OSCC cells in vitro. SIGNIFICANCE: In oral squamous cell carcinoma, a frequently fatal and increasingly common epithelial malignancy of the oral cavity, ET-1 is known to contribute to pro-migratory paracrine signalling between stromal fibroblasts and cancer cells. The ability of ET-1 to modulate the phenotype of human oral stromal fibroblasts, however, has not previously been reported. The findings presented here suggest that targeting the stromal endothelin system may be a viable and novel therapeutic strategy for invasive oral cancer.

The effect of mechanical strain on protease production by keratinocytes.

BACKGROUND: Intact skin is under constant tension, transmitted from the underlying dermis, but when tension is lost (i.e. upon wounding) protease activity is upregulated. OBJECTIVES: To investigate the effect of mechanical strain on protease production by both normal and transformed keratinocytes in vitro. METHODS: Keratinocytes were seeded on to membranes precoated with either type I or type IV collagen. After 48 h medium was replaced with serum-free medium and mechanical strain was applied. RESULTS: Mechanical strain resulted in decreased urokinase-type plasminogen activator (uPA) production by normal human keratinocytes (P<0.05) but increased production by transformed keratinocytes (P<0.05) cultured on type I and type IV collagen. CONCLUSIONS: Differential production of uPA by normal and transformed keratinocytes is relevant in the context of normal function, wound healing and tumorigenesis.

Transfection and ligation of CD40 in human oral keratinocytes affect proliferation, adhesion and migration but not apoptosis in vitro.

AIMS: CD40 expression is restricted to Keratinocytes of normal epidermis or stratified squamous epithelium of oral mucosa. Ligation of CD40 inhibits keratinocyte proliferation and apoptosis. The aim of this study was to investigate the functional significance of CD40 in the proliferation, apoptosis, adhesion and migration of human oral keratinocytes in vitro. METHODS: The CD40-negative oral keratinocyte line OSC19, its CD40-positive transfected derivative (OSC19T-CD40) and null transfectants (OSC19T-control), with and without stimulation by soluble protein CD40 ligand (sCD40L) or anti-CD40 antibodies were used. RESULTS: OSC19T-CD40 showed significantly (P < 0.001) slower growth than the null transfectants and parent cells. OSC19T-CD40 proliferation was inhibited by ligation with sCD40L and blocking by two anti-CD40 antibodies, but stimulated by a third. Binding of CD40 with ligand or antibody had no effect on keratinocyte apoptosis in any cell line. The capacity of OSC19T-CD40 cells to adhere to CD40L-coated wells was significantly greater (P < 0.001) than that of parent OSC19 and OSC19T-control cells, and the migration rate of OSC19T-CD40 cells was significantly higher than parent OSC19 (P = 0.038 on fibronectin, P = 0.004 on Matrigel) or OSC19T-control (P =0.017 on fibronectin, P = 0.013 on Matrigel) cells. CONCLUSIONS: CD40 is an important molecule in keratinocyte homeostasis, and has more than one ligand. The ligand that is bound may be critical in oral epithelial homeostasis, the development of malignancy and the behaviour of the subsequent tumour.

Transfection of CD40 in a human oral squamous cell carcinoma keratinocyte line upregulates immune potency and costimulatory molecules.

BACKGROUND: There is upregulation of class II molecules of the major histocompatibility complex (MHC) by keratinocytes in oral squamous cell carcinoma (OSCC) and inflammatory diseases such as lichen planus. The significance of this expression, or whether it is accompanied by upregulation of membrane-bound costimulatory molecules, is unknown. OBJECTIVES: To compare the expression of CD40, CD80, CD86, MHC class II and intercellular adhesion molecule-1 (ICAM-1), and the ability to induce allogeneic T-lymphocyte proliferation in vitro, of a CD40- OSCC cell line, its CD40+ transfected derivative and null transfectants. METHODS: OSCC cell lines and purified T lymphocytes were cocultured and T cell proliferation recorded. Phenotypes were analysed by flow cytometry. RESULTS: After T lymphocyte proliferation, which all OSCC cell lines were able to induce, there was upregulation of MHC class II and ICAM-1. However, the CD40+ transfectants were the most immunologically potent and were the only cells to show increased expression of CD86 (as well as further upregulation of CD40 and a statistically insignificant rise in CD80). The effects of blocking antibodies on T-cell proliferation were only statistically significant with the CD40+ transfectants. CONCLUSIONS: While not essential, expression of CD40 by OSCC cells is necessary for optimal induction of allogeneic T lymphocytes, possibly because of concurrent upregulation of other membrane-bound costimulatory molecules.

Cytokine-induced release of plasminogen activator inhibitor-1 by human mesothelial cells.

OBJECTIVE: To see what effect the inflammatory cytokines tumour necrosis factor (TNF), interleukin 1 (IL-1), and interleukin 6 (IL-6) had, both alone and in combination, on the production of plasminogen activator inhibitor 1 (PAI-1) by human mesothelial cells. DESIGN: Laboratory study. SETTING: University hospital, UK. MATERIAL: Six cell cultures of human mesothelial cells. MAIN OUTCOME MEASURES: Concentrations of PAI-1 in conditioned media and cell lysates after culture for 24 hours. RESULTS: TNF, IL-1, and IL-6 all significantly increased the amount of PAI-1 in the media compared with controls (81%, p < 0.05; 77%, p < 0.05; and 60%, p < 0.05, respectively). TNF and IL-1 together produced significantly more release than each cytokine alone (190%, p < 0.05) and a combination of the three increased release even further (290%, p < 0.05). The presence of endotoxin did not significantly affect the release of PAI-1. CONCLUSION: Inflammatory cytokines mediate the release of PAI-1 by mesothelial cells, and so may affect the deposition of fibrin within the peritoneal cavity.

Vascular smooth muscle cells potentiate plasmin generation by both urokinase and tissue plasminogen activator-dependent mechanisms: evidence for a specific tissue-type plasminogen activator receptor on these cells.

Plasminogen activators play a role in the response of the vessel wall to injury, presumably by mediating the degradation of extracellular matrix (ECM) by vascular smooth muscle cells (VSMCs) that is necessary for their migration and proliferation. We have therefore investigated the ability of VSMCs to assemble specific cell surface plasminogen-activating systems. Urokinase-type plasminogen activator (uPA) bound to a single class of site on VSMCs (kd, 2 nmol/L), binding of pro-uPA resulted in a large potentiation of plasmin generation and both were competed by antibodies to the uPA receptor (uPAR). Tissue-type plasminogen activator (tPA) also bound to VSMCs as determined by functional assay, with the binding isotherms showing two classes of binding site with apparent kds of 25 and 300 nmol/L. tPA binding to the higher affinity site caused a greater than 90-fold enhancement of the activation of cell bound plasminogen, whereas the lower affinity binding, mediated primarily by the ECM, had little effect on tPA activity. The high-affinity binding of tPA to VSMCs resulted in an eightfold greater potential for plasmin generation than the binding of uPA, with this difference increasing to 15-fold after thrombin stimulation of the cells due to a 1.8-fold increase in tPA binding. These data show a novel specific tPA receptor on VSMCs that may be important for the regulation of plasminogen activation in various vascular pathologies.

The structure of the human LIM protein ACT gene and its expression in tumor cell lines.

We describe the human ACT genomic and cDNA sequence which like its murine counterpart contains the defining secondary structure of the FHL (Four-and-a-Half LIM-domain) LIM-protein family. The coding region of the human ACT gene spans five exons. This distribution is very similar to the FHL1 gene and includes the arrangement of split codons across exon boundaries suggesting that these genes share a common ancestor. The human ACT gene was not detected by Northern analysis in the adult testis although this is the only known site of expression found with its murine counterpart. However, the human ACT gene was found to be expressed in a panel of human tumor cell lines derived from squamous cell carcinomas, melanomas, and leukemias. Interestingly, FHL1, FHL2, and FHL3 were also found to be expressed in some of these cell lines and the results suggest an important role for FHLs in tumor biology.

Peritoneal fibrinolytic activity and intra-abdominal adhesions.

The mechanisms leading to reduction of peritoneal fibrinolytic activity in conditions that are associated with the formation of intra-abdominal adhesions were studied. Tissue plasminogen activator was found, by antibody inhibition techniques, to be the activator of fibrinolysis in homogenates of control peritoneum (n = 6). Homogenates of control (n = 10) and inflamed peritoneum (n = 10) were analysed. Plasminogen activating activity was much lower in inflamed peritoneum (median 0.07 IU/cm2) than in control tissue (median 12.0 IU/cm2) (p less than 0.001). Levels of tissue plasminogen activator and alpha 2-antiplasmin were similar in both control and inflamed tissue. Plasminogen activator inhibitor-1, not detectable in control peritoneum, was present in inflamed tissue and might be the reason for the reduction in functional fibrinolytic activity.

Prediction of the delayed complications of intestinal and mesenteric injuries following experimental blunt abdominal trauma.

Injuries to the intestine and mesentery are often found in patients undergoing laparotomy for blunt abdominal trauma. Although treatment of perforations is relatively straightforward, the same is not true for contusions. Few guidelines exist at present to aid the surgeon in deciding which injuries require resection in order to avoid the complications of delayed perforation and late stricture formation. The natural history of these non-perforating intestinal and mesenteric injuries has been examined in an experimental model to identify possible criteria on which future management can be based. In the immediate postinjury period peristalsis and local mesenteric pulsation were absent in the majority of injuries which went on to full recovery and these observations are thus of little predictive value in predicting outcome. The initial size of contusion (length of contusion along longitudinal axis of bowel) relative to bowel wall circumference (BWC) was related to complications as follows: contusion less than BWC (n = 47)--one complication; contusion greater than BWC (n = 8)--three complications (P = 0.02). Similarly, six mesenteric injuries which produced an initial ischaemia (assessed by fluorescein) less than twice the BWC did not result in any complications, compared with four complications which occurred in ten cases when the initial ischaemia was greater than twice the BWC. These results go some way towards providing a better understanding of these injuries and in turn may help the emergency surgeon in deciding which injuries require resection.

Human intraperitoneal fibrinolytic response to elective surgery.

Intra-abdominal adhesions develop in over 90 per cent of patients undergoing laparotomy. Peritoneal fibrinolysis is believed to be important in the pathophysiology of adhesion formation. This study investigated the fibrinolytic response of postoperative peritoneal fluid in 12 patients undergoing elective laparotomy. There was a significant reduction in the plasminogen activating activity to undetectable levels at 24 h, which was sustained at 48 h (P < 0.05). While there was an early reduction in the concentration of tissue plasminogen activator (median 40.0, 28.2, 16.3 and 31.9 ng/ml at 2, 6, 24 and 48 h respectively; P < 0.05), the abolition of functional fibrinolytic activity appeared to be secondary to a marked increase in the concentration of plasminogen activator inhibitor (PAI) 1 (median 86, 196, 800 and 730 ng/ml at 2, 6, 24 and 48 h respectively; P < 0.05) and PAI-2 (median less than 6, 12, 155 and 245 ng/ml at 2, 6, 24 and 48 h respectively; P < 0.05). This reduction in the plasminogen activating activity of peritoneal fluid may favour the formation of permanent fibrous adhesions following surgery.

Plasminogen activator inhibitor-2 expression in inflamed appendix.

Plasminogen activator inhibitors are thought to be responsible for the abolition of fibrinolytic activity in inflamed peritoneum. This reduction in the fibrin clearing capacity of the peritoneum promotes the formation of intra-abdominal adhesions. High concentrations of plasminogen activator inhibitor-2 (PAI-2) have been previously found in inflamed peritoneal tissue using immunoassays, but it is undetectable in normal peritoneum. The aim of this study was to localize plasminogen activator inhibitor-2 production in tissue by in situ mRNA hybridisation. Sections of normal and inflamed human appendix were hybridised with a digoxigenin labelled cDNA probe. In normal appendix staining was confined to macrophages in the mucosa. Macrophage staining was also seen in inflamed tissue but with a wider distribution throughout the appendix wall. PAI-2 was also localized to mesothelial cells of inflamed but not normal appendix. Cell identities were confirmed using immunohistochemistry directed against cell specific markers. Staining was absent from control slides incubated with plasmid DNA or PAI-2 probe following ribonuclease digestion. The identification of the cells expressing the PAI-2 gene in peritoneum increases our understanding of the pathophysiological process leading to fibrin deposition within the abdomen during peritonitis.

Fibrinolysis and the biliary tree.

AIMS: To investigate the fibrinolytic activity of normal and calculous human bile. METHODS: Fibrinolytic properties of the biliary tract were studied in patients with gall bladder stones (n = 7) compared with acalculous gall bladders (n = 8). RESULTS: Bile plasminogen activating activity was detected in a wide range in both groups (calculous bile median 0.35 IU/ml; range: 0.06-6.59, versus normal bile 0.70 IU/ml; 0.19-3.56). There was no difference in the bile concentration of tissue plasminogen activator between the two groups (calculous bile median 21.5 ng/ml versus normal bile 9.5 ng/ml), which was present in much greater concentrations than urokinase (calculous bile median 0.10 ng/ml versus normal bile 0.36 ng/ml). Both plasminogen activators were detected in low concentrations in gall bladder mucosa. Plasminogen activator inhibitors-1 and 2 were detected in bile in significantly greater concentrations in patients with gall bladder stones (plasminogen activator inhibitor-1: calculous bile median 15 ng/ml versus normal bile < 2 ng/ml, plasminogen activator inhibitor-2: 157 ng/ml versus < 6 ng/ml, p < 0.05). CONCLUSIONS: Human bile possesses fibrinolytic activity and the principal plasminogen activator in bile seems to be tissue plasminogen activator. Plasminogen activator inhibitors were present in greater concentrations in stone bile and may be a factor in the pathogenesis of gall stone formation.

Effect of experimental peritonitis and ischaemia on peritoneal fibrinolytic activity.

OBJECTIVE: Measurement of the fibrinolytic response of the peritoneum to experimental peritonitis and ischaemia. DESIGN: Controlled study SETTING: Academic surgical unit, UK MATERIAL: Male Wistar rats INTERVENTIONS: Peritoneal injuries were caused in four groups of male Wistar rats (n = 35 in each group): (1) control group ("open and close" laparotomy); (2) bacterial peritonitis (mixed faecal flora); (3) chemical peritonitis (10 mg/ml tetracycline) and; (4) ischaemic peritoneum (ligated peritoneal buttons). Peritoneal biopsy specimens were taken from five animals in each group at seven time intervals and plasminogen activating activity (PAA) measured by fibrin plate assay. RESULTS: Compared with the control group the three peritoneal injuries produced a uniform reduction in PAA during the first 6 and 12 hours: at 6 hours the median PAA was 0.029 IU/cm2 for bacterial peritonitis, 0.021 IU/cm2 for chemical peritonitis, and 0.05 IU/cm2 for ischaemic peritoneum compared with 0.112 IU/cm2 for the control group; p < 0.001, ANOVA. At 12 hours the median PAA was 0.024 IU/cm2 for bacterial peritonitis, < or = 0.014 IU/cm2 for chemical peritonitis, and 0.05 IU/cm2 for ischaemic peritoneum compared with 0.112 IU/cm2 for the control group; p < 0.001, ANOVA. There then followed a rebound peak in all groups, maximal at 4-7 days, before a return to baseline values at two weeks. CONCLUSION: Peritoneal fibrinolysis was appreciably inhibited after three different standardised peritoneal injuries. The data support the hypothesis that there is a single pathophysiological mechanism of adhesion formation.

Plasminogen activator inhibitor 2 reduces peritoneal fibrinolytic activity in inflammation.

Fibrinolysis in peritoneal tissue may play a role in the development of intra-abdominal adhesions. The plasminogen-activating capacity of human peritoneum results largely from the presence of tissue plasminogen activator (tPA). Inflammation reduces peritoneal plasminogen-activating activity and leads to the appearance of plasminogen activator inhibitor (PAI) type 1. The role of PAI-2 in the inhibition of peritoneal fibrinolysis during inflammation was investigated in this study. The plasminogen-activating activity of peritoneal biopsy homogenates (seven inflamed, seven normal), measured using a fibrin plate technique, was reduced in inflamed compared with normal tissue (median < 0.07 versus 13.9 units/cm2, P < 0.01); tPA antigen levels were not significantly different (median 1.02 versus 1.34 ng/ml). PAI-1 and PAI-2 antigens were not detected in normal human peritoneum but were present in inflamed peritoneum (median concentration 8.8 ng/ml for PAI-1, 26.7 ng/ml for PAI-2). These inhibitors may be important factors in adhesion formation by contributing to the abolition of peritoneal plasminogen-activating activity.

The operative peritoneal fibrinolytic response to abdominal operation.

OBJECTIVE: To measure changes in the fibrinolytic properties of human peritoneum during operation. DESIGN: Open study. SETTING: University hospital, UK. SUBJECTS: 20 patients undergoing elective operations for non-inflammatory disease. INTERVENTIONS: Peritoneum was biopsied at the beginning and end of operation. MAIN OUTCOME MEASURES: Peritoneal plasminogen activating activity (PAA) and the concentrations of tissue plasminogen activator (t-PA), urokinase, and plasminogen activator inhibitors 1 and 2 were measured at both time points. RESULTS: Peritoneal PAA was reduced over the time of the operation (p < 0.05) as was the concentration of t-PA (p < 0.05). The urokinase concentration rose significantly (p < 0.05), but plasminogen activator inhibitors 1 and 2 were not detected. CONCLUSIONS: Elective abdominal operation caused an immediate reduction in peritoneal PAA which seemed to be secondary to a reduced concentration of t-PA. Such a reduction in peritoneal fibrinolytic activity allows the early deposition of fibrinous deposits within the peritoneal cavity.