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A phospholipase A2 (PLA2, EC 3.1.1.4) was purified from human cell-free ascitic fluid (a-PLA2) by ion-exchange chromatography and h.p.l.c. on a reverse-phase column to apparent homogeneity. The enzyme had an Mr of approx. 10,000 as determined by SDS/PAGE. Polyclonal antibodies raised in a rabbit were specific to a-PLA2, as judged by immunoblotting. A time-resolved fluoroimmunoassay (TR-FIA) for measuring the concentration of a-PLA2 in various body fluids was developed. The detection limit of the assay was about 6 ng/ml. The antiserum did not cross-react with pancreatic secretory phospholipase A2 as measured by TR-FIA. The enzyme content was studied in various samples, including normal human serum, buffy-coat leucocytes, synovial fluid, and pancreas and spleen homogenates.

Phospholipase A2 has been implicated in the pathogenesis and pathophysiology of acute pancreatitis. The initial enthusiasm concerning pancreatic group I phospholipase A2 as an enzyme responsible for pancreatic necrosis and systemic manifestations of acute pancreatitis has gradually waned, as the mechanisms of the pathogenesis and the pathophysiology of acute pancreatitis have been revealed. The overactive systemic inflammatory response associated with the activation of different cascade systems and increased levels of inflammatory mediators as seen in severe acute pancreatitis, closely resembles that associated with other severe inflammatory diseases such as septic shock. The critical role of the non-pancreatic secretory group II phospholipase A2 in the chain of inflammatory mediators has been emphasized recently, as new detection methods for the enzyme have become available.

Group II phospholipase A2 (PLA2) is an enzyme that has marked antibacterial properties in vitro. To define the role of group II PLA2 in the defense against Staphylococcus aureus, we studied host responses in transgenic mice expressing human group II PLA2 and group II PLA2-deficient C57BL/6J mice in experimental S. aureus infection. After the administration of S. aureus, the transgenic mice showed increased expression of group II PLA2 mRNA in the liver and increased concentration of group II PLA2 in serum, whereas the PLA2-deficient mice completely lacked the PLA2 response. Expression of human group II PLA2 resulted in reduced mortality and improved the resistance of the mice by killing the bacteria as indicated by low numbers of live bacteria in their tissues. Human group II PLA2 was responsible for the bactericidal activity of transgenic mouse serum. These results suggest a possible role for group II PLA2 in the innate immunity against S. aureus infection.

Group II phospholipase A2 has been proposed to play an important role in the pathophysiology of inflammatory bowel diseases. This enzyme has also been linked to host defence mechanisms against bacteria. The current study aimed at measuring the mass concentrations of group II phospholipase A2 in serum and colonic mucosa of patients with Crohn's disease of different severity and of appropriate control patients without any inflammatory disease. The activity of the disease was determined by clinical factors (the simple index score) and endoscopic and histological scoring. The mass concentration of group II phospholipase A2 was measured by a time-resolved fluoroimmunoassay. The mass concentrations of group II phospholipase A2 in serum and colonic mucosa were significantly higher both in patients with active and inactive Crohn's disease when compared with controls. There was statistically significant difference in the mass concentration of group II phospholipase A2 in colonic mucosa but not in serum between inactive and active Crohn's disease. The current results indicate that the mass concentration of group II phospholipase A2 is increased in serum and colonic mucosa of patients with Crohn's disease and that the latter is associated with the degree of the inflammatory activity in the intestinal wall. These results support the idea that group II phospholipase A2 is involved in the local and generalised pathological processes of Crohn's disease.

A case of tubulovillous adenoma in the rectum of a 51-year-old man is presented. The tumour contained numerous Paneth cells which formed well-developed glands in the basal areas. Group II phospholipase A2 and lysozyme were found in the tumour cells by immunohistochemistry. mRNA of group II phospholipase A2 was localized in the tumour cells by in situ hybridization. It was concluded that a considerable part of this rare type of tumour consisted of Paneth cells which were capable of synthesizing group II phospholipase A2.

Group II phospholipase A2 (PLA2) is a lipolytic enzyme suggested to play a role in inflammation and antibacterial defence. In seminal fluid, the concentration of PLA2 is exceedingly high under normal circumstances (about 1,000 times the concentration in blood plasma of healthy humans). To elucidate the origin of the enzyme present in seminal plasma, we investigated the expression of group II PLA2 in male reproductive organs both at protein and mRNA levels. In addition, the presence of the enzyme was studied in common male genital tumors.The methods used were immunocytochemistry, in situ hybridization, and Northern blotting.Northern blotting gave positive results for group II PLA2 mRNA in normal prostate, whereas other normal genital tissues gave negative results. Immunohistochemistry and in situ hybridization of group II PLA2 gave identical results. The enzyme was produced exclusively by the secretory epithelial cells of the prostatic gland. Surprisingly, expression was restricted to the posterior lobe and paraurethral glands of the prostate. Cells of prostatic adenocarcinoma expressed group II PLA2, whereas cells of other male genital tumors contained neither the enzyme protein nor the mRNA of group II PLA2. In some cases prostatic cancer cell seemed to express group II PLA2 at a higher rate than normal prostatic gland cells.The high content of group II PLA2 in seminal plasma is due to the local production and secretion of the enzyme by the epithelial cells of the prostatic glands. Group II PLA2 is expressed focally, suggesting that specialized prostatic glands secrete this enzyme. All prostatic adenocarcinomas tested expressed group II PLA2 in variable amounts.

To investigate the catalytic activity of phospholipase A2 in serum during the early phase of experimental fat embolism.Randomised controlled experimental study.Animal laboratory, Finland.18 domestic pigs weighing 25-31 kg.Allogeneic bone marrow suspension at a dose of 100 mg/kg was infused intracavally in 9 anaesthetised, mechanically ventilated, and haemodynamically monitored pigs; 9 control pigs received saline.Central haemodynamics, blood gases, catalytic activity of phospholipase A2.In the fat embolism group, there were significant increases in mean pulmonary arterial pressure (p0.001), pulmonary vascular resistance (p0.001) and pulmonary shunting (p0.05) and simultaneously, systemic oxygenation was significantly impaired. The animals with fat embolism developed gradual fever and leucocytosis, whereas the catalytic activity of phospholipase A2 remained relatively unchanged.In this experimental model the measurement of serum phospholipase A2 activity does not provide a useful tool for the early detection of experimental fat embolism.

The aim of this study was to demonstrate the synthesis and cellular distribution of group II phospholipase A2 and lysozyme in the main and accessory lacrimal glands.The authors studied samples of normal main lacrimal glands of seven autopsied subjects and accessory lacrimal glands of eight patients who underwent ptosis surgery. The specimens were immunostained with a rabbit antiserum against group II phospholipase A2 and a monoclonal antibody against lysozyme. Expression of group II phospholipase A2 gene was shown using Northern hybridization and in situ hybridization.Lysozyme was present in the secretory granules of most acini, whereas group II phospholipase A2 was seen in a minority of acinar cells, primarily in the central parts of lobules in the main and accessory lacrimal glands. Synthesis of group II phospholipase A2 in the glandular cells was confirmed by Northern hybridization and by in situ hybridization.There are two specialized cell types in the main and accessory lacrimal glands, one synthesizing group II phospholipase A2 and the other synthesizing lysozyme. These enzymes are important nonspecific antibacterial factors in tears.

Phospholipase A2 values increase in serum in various inflammatory states, infections, and postoperatively in surgical patients. Several organs, including the liver and spleen have been suggested as sources of circulating phospholipase A2. The purpose of the present work was to examine the possible role of the spleen as a source of elevated serum concentrations of phospholipase A2 after surgery. Pre- and postoperative serum samples of patients undergoing splenectomy were studied for group I phospholipase A2, group II phospholipase A2, and C-reactive protein mass concentrations and catalytic activity concentration of phospholipase A2. The catalytic activity concentration of phospholipase A2 and the mass concentrations of group II phospholipase A2 and C-reactive protein increased postoperatively (8.08 +/- 1.40 U/l vs. 3.96 +/- 0.89 U/l (mean +/- SEM) for phospholipase A2 catalytic concentration (p0.03), and 154.8 +/- 32.1 micrograms/l vs. 47.5 +/- 14.7 micrograms/l (mean +/- SEM) for group II phospholipase A2 mass concentration (p0.02, n = 7). The mass concentration of group I phospholipase A2 remained unchanged. The catalytic concentration of phospholipase A2 correlated well with the mass concentration of group II phospholipase A2 (p0.001, r = 0.846, n = 43). The concentration of C-reactive protein correlated well with the mass concentration of group II phospholipase A2 (p0.001, r = 0.566, n = 43) in serum. The results indicate that group II phospholipase A2 is released into the circulation after splenectomy, and the spleen seems not to be the source of circulating group II phospholipase A2.

The concentration of group II phospholipase A2 was measured in blood plasma samples before and after liver transplantation in a 27-year-old woman who suffered from a massive epitheloid hemangioendothelioma of the liver. The pretransplantation concentration of group II phospholipase A2 was 830 microg/L, which is markedly above the upper limit of the reference interval (10.8 microg/L). After the transplantation, there was a dramatic decrease in the group II phospholipase A2 level (33 microg/L on the first posttransplantation day). In situ hybridization of mRNA and immunohistochemistry revealed synthesis of group II phospholipase A2 in hepatocytes in non-neoplastic areas of the liver. Tumor cells did not contain group II phospholipase A2. The results indicate that group II phospholipase A2 circulating in blood plasma originates in hepatocytes.

Twenty-two hospitalized patients, diagnosed as having hypertensive disorder of pregnancy, were selected from two University Clinics. Maternal serum samples were analyzed for serum group II phospholipase A2 (PLA2-II) by time-resolved fluoroimmunoassay. At the same time, umbilical artery blood flow velocities were measured with color Doppler sonography for orientation and pulsatile Doppler sonography for recording waveforms. Nineteen normotensive third-trimester pregnant patients served as a control group. Maternal serum PLA2-II was elevated in 8 cases with preeclampsia. This elevation was invariably associated with decreased blood flow velocity in the umbilical artery. In 1 case, the clinical condition allowed simultaneous follow-up of serum enzyme and blood flow velocity: a further rise of serum PLA2-II was linked to a further decrease in the blood flow velocity of the umbilical artery. A large spillover of the elevated PLA2-II content from the preeclamptic placenta into the maternal serum is associated with a decrease in blood flow velocity in the umbilical artery. The enzyme might serve as a link between local proximal (placenta) and systemic distal (umbilical arterial blood flow) effectors.

It has been suggested that group II phospholipase A2 (PLA2-II) plays an essential role in inflammation, but the cellular source(s) of the enzyme is (are) largely unknown.Expression of PLA2-II was analyzed in human gastrointestinal tract at both protein and mRNA levels. Both normal tissues and specimen from patients with a few different common gastrointestinal disorders were analyzed.Expression of PLA2-II mRNA was seen in the Paneth cells but not in any other cell type of the intestinal tract. Blood vessel walls showed PLA2-II immunoreactivity but were negative in in situ hybridization for PLA2-II mRNA.It was concluded that nonpancreatic group II PLA2 is synthesized and stored by Paneth cells, whereas other cell types of the gastrointestinal tract seem incapable of synthesis of this enzyme. The positive immunoreaction in vascular structures may reflect the entry of circulating PLA2-II into vessel walls rather than local production of the enzyme.

Pancreatic acinar cell carcinoma is a rare neoplasm (comprising about 1% of pancreatic tumours). We studied three cases (61-year-old female; 42-year-old male; 57-year-old male), whose survival after diagnosis ranged from 1 year 2 months to 6 years 8 months. There were widespread metastases in each case. The tumours had acinar, trabecular and solid growth patterns. By immunohistochemistry, pancreatic acinar cell markers including carboxyl ester lipase, pancreatic secretory trypsin inhibitor and pancreatic phospholipase A2 (group I PLA2) gave a strong positive reaction in all three cases. By electron microscopy, zymogen granules were seen in the cytoplasm of the tumour cells. Immunostaining for prostate-specific antigen was positive in all three cases. Above-normal concentrations of pancreatic PLA2 were measured in the serum of one patient and the values decreased during chemotherapy concomitantly with the reduction in the size of the tumour mass. In conclusion, immunohistochemical demonstration of the secretory products of acinar cells including the new marker pancreatic PLA2 is useful in the differential diagnosis of pancreatic acinar cell carcinoma. Determination of the concentration of pancreatic group I PLA2 in serum may be helpful in the evaluation of therapy.

We compared the predictive value of determining group II phospholipase A2 (PLA2) in serum for diagnosing acute appendicitis with the predictive values of white blood cell count (WBC) and measurement of C-reactive protein (CRP). In this prospective study, we included 186 patients who were undergoing appendectomy after clinical diagnoses of acute appendicitis. The performance of each test was measured by receiver-operating characteristic curves. WBC was the test of choice in diagnosing uncomplicated acute appendicitis. However, in contrast to CRP and PLA2, which increased in patients with protracted inflammation, there was not a concomitant increase in WBC. Therefore, especially CRP, but also PLA2, were better indicators of appendiceal perforation or abscess formation than was WBC. Increased WBC, CRP, and PLA2 values did not unequivocally corroborate the clinical suspicion of appendicitis, but if all three values were within normal limits, acute appendicitis could be excluded with a 100% predictive value. PLA2 values showed a highly significant correlation with CRP but not with WBC values, which supports the view that PLA2 represents an acute-phase reactant.

Tears are known to have antimicrobial properties. The authors investigated the presence of the antibacterial enzyme phospholipase A2 (PLA2) in tears and lacrimal glands.The catalytic activity of PLA2 and the amount of pancreatic group 1 PLA2 and nonpancreatic group 2 PLA2 were measured in homogenates of eight human lacrimal glands from autopsied subjects and in tears from four healthy volunteers. The localization of PLA2s in lacrimal gland sections was studied by immunohistochemistry. Skeletal muscle was used as a control.The catalytic activity of PLA2 was significantly higher in lacrimal glands than in skeletal muscle. Immunochemical analysis showed significantly higher amounts of group 2 PLA2 in lacrimal gland than in skeletal muscle homogenates. Group 1 PLA2 was present in trace amounts only. The concentration of group 2 PLA2 in tears was high (1451.3 micrograms/l) compared to that in the serum of healthy individuals (3.7 micrograms/l). By immunohistochemistry, a granular reaction of group 2 PLA2 was localized in the glandular cells of lacrimal glands. The apical cytoplasm of many duct cells also was labeled.The lacrimal glands secreted nonpancreatic group 2 PLA2, which most likely acts as an antiinfectious factor in tears.

Phospholipase A2 (EC 3.1.1.4; PLA2) is detected in serum by determination of either the catalytic activity of the enzyme or the concentration of the enzyme protein by immunoassays. The most sensitive methods for determining PLA2 catalytic activity are radiometric assays, with a substrate of synthetic phospholipid (e.g., phosphatidylcholine or phosphatidylethanolamine) containing a 14C- or 3H-labeled fatty acid at the sn-2-position. Membranes of autoclaved Escherichia coli grown in the presence of radioactive oleic acid may also be used as a substrate. The released fatty acids are separated from the unreacted substrate and quantified by liquid scintillation counting. PLA2 catalytic activities are increased in serum in sepsis, acute pancreatitis, peritonitis, multiple injuries, rheumatoid arthritis, and other arthropathies. Immunoassays--radioimmunoassay, enzyme-linked immunosorbent assay, or time-resolved fluoroimmunoassay--are based on the use of either polyclonal or monoclonal antibodies to purified PLA2s. Specific assays have been developed for both pancreatic group I PLA2 (PLA2-I) and nonpancreatic group II PLA2 (PLA2-II). The cellular source of PLA2-I in serum is the pancreatic acinar cell. Increased serum PLA2-I values have been reported in acute pancreatitis, pancreatic cancer, and abdominal trauma. Increased PLA2-II values are found in conditions involving inflammation, e.g., sepsis, infections, acute pancreatitis, various forms of arthritis, cancer, complications of pregnancy, and postoperative states. Good correlations have been found in serum samples between the catalytic activity of PLA2 and the concentration of PLA2-II but not PLA2-I. PLA2-II may represent an acute-phase protein. The cellular source of the PLA2-II in serum is unknown; it is present in large amounts in cartilage and Paneth cells, prostatic gland cells, seminal fluid, lacrimal gland cells, and tears, but cannot be demonstrated by immunohistochemical or immunochemical methods in inflammatory cells.

Summary. Phospholipase A2 (PLA2) was analysed in seminal plasma of fertile, subfertile, and vasectomized men as well as in prostatic secretion and tissue. Immunological cross-reactivity was observed between synovial-type PLA2 antiserum and the enzyme present in seminal plasma. There was a highly significant correlation between the concentration of the synovial-type PLA2, as measured by a time-resolved fluoroimmunoassay and the catalytic activity of the PLA2. The results show that the PLA2 content in human seminal plasma is very high (approximately 1000 times of that present in blood plasma) and that the enzyme belongs to the synovial-type group II phospholipase A2. The results also indicate that the enzyme is secreted by the prostate.

Phospholipase A2 (PLA2) was produced in E. coli by a recombinant technique using a synthetic gene coding for PLA2 found in synovial fluid (SF) of patients suffering from rheumatoid arthritis (RA). Polyclonal antibodies were produced against the recombinant synovial type PLA2 (syn-PLA2) in a rabbit. The IgG fraction of the antiserum was isolated and the specificity was tested by immunoblotting. The antiserum detected a protein with an apparent molecular weight of 15 kDa in extracts of cartilage, but did not react with PLA2 isolated from human pancreas or ascitic fluid. In immunohistochemistry, the anti-syn-PLA2 antibody decorated chondrocytes and matrix of articular, laryngeal and auricular cartilage, but did not decorate synovial tissue or its contained inflammatory cells in RA or other human tissues tested (pancreas, liver, thyroid, tonsil, lung, nasal polyp, skin, placenta, myometrium, bone). The results show that syn-PLA2 is present both in articular and extraarticular cartilage and support the view that PLA2 found in SF might originate from chondrocytes, and not from synovial lining or inflammatory cells.

The most important fatal complications of acute pancreatitis are respiratory dysfunction and anuria. Phospholipase A2 has been postulated to be associated with pathologies of various diseases, such as acute pancreatitis, septic shock and multiple injuries. We have recently developed immunoassays for the measurement of pancreatic and nonpancreatic synovial-type phospholipase A2. The present prospective study on 35 consecutive patients with acute pancreatitis indicated that the concentration of synovial-type phospholipase A2, the catalytic activity of phospholipase A2 and the concentration of C-reactive protein in serum were significantly higher in those patients suffering from acute pancreatitis who needed respirator treatment than in those who managed with spontaneous breathing, while there was no difference between these groups in the concentration of pancreatic phospholipase A2. The only significant difference between patients whose highest creatinine concentration rose up to 140 mumol/l and those whose highest creatinine concentration remained below this cutoff value was in their synovial-type phospholipase A2 values. The increased concentration of nonpancreatic synovial-type phospholipase A2 in serum was associated with pulmonary and renal complications. These results emphasize the role of synovial-type phospholipase A2 in the pathophysiology of acute pancreatitis.

A monoclonal antibody, designated 2E1, against human pancreatic phospholipase A2 was produced by hybridization of myeloma cells with spleen cells of immunized BALB/c mice. The hybridomas were screened for antibody production by time-resolved fluoroimmunoassay (TR-FIA). The antibody was found to belong to subclass I of murine IgG. The specificity of the antibody was confirmed by immunohistochemistry of pancreatic and other tissues, by immunoblotting of a crude aqueous extract of human pancreas and purified human pancreatic phospholipase A2 and by TR-FIA. A solid-phase time-resolved fluoroimmunoassay was developed by using the monoclonal anti-phospholipase A2 antibody as the catching antibody and a polyclonal sheep anti-phospholipase A2 antibody labelled with europium as the detecting antibody. The validity of the new TR-FIA of human pancreatic phospholipase A2 was confirmed by using it to measure the phospholipase A2 concentrations in serum samples from healthy subjects and from patients suffering from acute pancreatitis.

Phospholipase A2 (PLA2) is a key enzyme in the metabolism of phospholipids. PLA2 is enriched in neuronal membranes and plays an essential role in the functioning of membrane structures in the brain. Because a disordered phospholipid metabolism has been postulated in schizophrenia we started in 1985 a series of exploratory studies in an attempt to clarify the role of PLA2 in schizophrenic disorders. Our results can presently be summed up as follows: 1. Drug-free schizophrenics showed significantly higher PLA2 activity in serum and in plasma as compared with healthy controls as well as with nonschizophrenic psychiatric patients; the latter did not differ from the control group with regard to PLA2 activity. These findings suggest that increased PLA2 activity might be specific for schizophrenia. 2. The possibility that increased PLA2 activity is an artifact due to prior neuroleptic treatment could be ruled out as improbable by the findings that a) neuroleptic treatment significantly reduced PLA2 activity, and b) increased PLA2 activity was also found in first-onset, never-treated schizophrenic patients. 3. Increased PLA2 activity in schizophrenic patients was not caused by the entry of pancreatic enzyme into circulation. Our findings in serum rather suggest that the increment reflects increased intracellular enzyme activity. We speculate that our results might reflect an increment of the intraneuronal PLA2 activity in the brain. The activation of PLA2 in the brain was found to result in changes in neuronal function due to alterations in receptor sensitivity as well as in neurotransmitter metabolism. The possibility that such PLA2-induced mechanisms are involved in the pathology of schizophrenia should be investigated in further experiments.

Several studies suggest that the activation of pancreatic phospholipase A2 (PLA2) and its release from injured acinar cells play an important role in the pathogenesis of acute pancreatitis. Elevated catalytic activity of PLA2 in serum is associated especially with severe forms of the disease. PLA2 has been purified from human cadaver pancreas and an antiserum raised against the enzyme in rabbits. Immuno-histochemical localization of PLA2 in pancreatic tissue was abnormal in acute pancreatitis. A time-resolved fluoroimmunoassay for human pancreatic PLA2 has been developed. Increased serum concentrations of immunoreactive PLA2 were found in acute pancreatitis during the first week after hospital admission. The values returned to normal somewhat more slowly than corresponding serum amylase values. The immunochemical determination of PLA2 in serum provides a fast and specific detection of injury to pancreatic acinar cells. The pancreas is not the only source of PLA2 in acute pancreatitis. The nonpancreatic PLA2 may originate from various inflammatory cells, but this hypothesis remains to be proven.

Several studies suggest that phospholipase A2 (PLA2) plays an important role in the pathology of acute pancreatitis. PLA2 is activated within the pancreas in experimental and human acute pancreatitis. Elevated catalytic activity of PLA2 in serum is associated especially with the severe forms of the disease. The pancreas seems not to be the only source of the enzyme entering the circulation in acute pancreatitis. The source of the non-pancreatic PLA2 may be various inflammatory cells, but this hypothesis remains to be proven. The results of the treatment of experimental acute pancreatitis with PLA2 inhibitors have been promising, but adequate human trials have not been conducted.

We describe an immunofluorometric assay for human pancreatic phospholipase A2 based on time-resolved fluorescence. The labeled antibody technique in combination with the time-resolved 1-s fluorometric detection of the europium label, which essentially eliminates all background fluorescence, resulted in a high sensitivity (20 ng/L) and a wide (5000-fold) linear range. Nonspecific binding was minimized by treating the solid-phase antibody with NaSCN before coating, to remove endogenous antigen, and by immunosorbent purification of the antibody before labeling with europium. This is a one-incubation, multi-site, solid-phase assay on polystyrene microtiter strips, even though a polyclonal antibody was used. As measured by this assay, activity of immunoreactive phospholipase A2 was found to be above normal in sera of patients suffering from acute pancreatitis.

We purified human pancreatic phospholipase A2 from postmortem pancreatic tissue by elution of the semi-purified enzyme on CM-Sephadex C-25 with a linear NaCl gradient at pH 6.0. The enzyme appeared as a single polypeptide chain with an isoelectric point of 9.2 +/- 0.1. The relative molecular mass of the enzyme was estimated to be 15 800 +/- 1000 by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The enzyme is resistant to heating and to a 25 g/L concentration of sodium dodecyl sulfate. It is inhibited by Ca2+ ions in the presence of ovolecithin and deoxycholate. By immunohistochemical methods we showed the enzyme to be localized in the apical zymogen granule portion of pancreatic acinar cells.

Measuring the content of immunoreactive pancreatic phospholipase A2 (PLA2; EC 3.1.1.4) and the catalytic activity of PLA2 in serum samples from five patients with acute pancreatitis, we found no correlation between these two measurements overall. To test the specificity of the method for catalytic PLA2, we measured PLA2 activity in serum samples before and after immunoadsorption with an antiserum to human pancreatic PLA2. The results suggest the presence of at least two immunologically distinct PLA2 enzyme proteins in sera from these patients. One of the enzymes is pancreatic in origin and may exist in active, inactive, or inhibited form. The activity profile of the second PLA2 enzyme in serum during acute pancreatitis differs from that for other common pancreatic enzymes. In the present experiment, the catalytic activity was not removed by treatment with the anti-human pancreatic PLA2 antiserum. The source of this second PLA2 activity is unknown. Some samples contained increased activities of both PLA2 forms.

Porcine pancreatic phospholipase A2 (PLA2) was immobilized to Sepharose 4B and porcine serum was passed through this affinity column. Bound substances were eluted by an EDTA-containing buffer and fractionated in a Sepharose 6B column. A single protein peak of the eluate from the latter column was found to inhibit PLA2 activity in a dose-dependent manner in an assay system using radioactive lecithin as a substrate and porcine pancreatic PLA2 as the enzyme source. The serum fraction containing the PLA2 inhibitory protein(s) (PIP) appeared inhomogeneous on SDS-polyacrylamide gel electrophoresis with two major bands close to each other, corresponding to a molecular weight of approximately 60,000. It was concluded that PIP might act as a protective principle against autodigestion in acute pancreatitis and other inflammatory diseases as well as playing a regulatory role in prostaglandin metabolism.

Immunoreactive phospholipase A2 (EC 3.1.1.4) was measured by a new sensitive time-resolved fluoroimmunoassay in the serum of 58 healthy subjects and 103 patients with acute pancreatitis. Patients with acute pancreatitis were grouped according to the etiology and clinical severity of the disease. The mean phospholipase A2 concentration in the reference (healthy) group was 5.5 (SD 1.9) micrograms/L. In acute pancreatitis the mean phospholipase A2 concentration was increased on the first day after hospital admission in all groups, and returned to normal somewhat more slowly than did serum amylase, especially in the patients with severe alcoholic pancreatitis. In this latter group the mean concentration of serum phospholipase A2 on the first day was 42.6 (SD 29.5) micrograms/L. In patients with pancreatic cancer, serum phospholipase A2 was 29.2 (SD 21.3) micrograms/L. The phospholipase A2 and amylase values were closely associated in all groups. The clinical sensitivities were 90.9% for severe alcoholic pancreatitis and 87.5% for pancreatic cancer. Immunochemical determination of phospholipase A2 in serum provides fast and specific detection of injury to pancreatic acinar cells. In addition to the early diagnosis of acute pancreatitis, follow-up determinations of phospholipase A2 seem to be useful in differentiating between mild and severe forms of pancreatitis.