Fine structure of the organic matrix of human pancreatic stones

Pancreatic stones that were removed from the pancreatic ducts of patients with chronic calcifying pancreatitis were decalcified so the organic matrix could be studied by scanning and transmission electron microscopy. The observations made by scanning electron microscopy were compared with those made on undecalcified stones, and the findings were correlated with light microscopic observations. After the calcium carbonate was removed, the stones consisted of multiple partitions arranged like a sponge. They were embedded in a gel-like matrix. The organic partitions frequently were composed of dense surface layers and sparse central reticular accumulations, which had surrounded and bound calcium carbonate crystals. The organic matrix was heterogeneous in texture. Some areas had dense, regular, proteinaceous fibrous material. Deposits resembling fibrin were observed. Altered cellular constituents appeared to make up minor portions of the matrix. Calcium carbonate, which was precipitated in vitro in pancreatic juice, resembled the morphology of pancreatic stones more than that of pure calcium carbonate crystals. These results are consistent with the coformation of pancreatic stones from constituents in the pancreatic juice [including pancreatic stone protein (PSP), glycosaminoglycans, and occasional cells] and precipitated calcium carbonate.     

Immunochemical characterization and quantitative distribution of pancreatic stone protein in sera and pancreatic secretions in pancreatic disorders.

A fluorometric immunoassay has been established to quantitate pancreatic stone protein providing a sensitivity for concentrations from 0.015 to 0.5 micrograms/mL. When concentrations of pancreatic stone protein were determined from pancreatic secretions obtained either from patients suffering from chronic pancreatitis (n = 31) [including the calcifying forms (n = 10)], pancreatic cancer (n = 22), or nonpancreatic diseases (n = 17), no significant differences were found. In contrast, increased concentrations were found in serum samples from patients with chronic (39/66) and acute pancreatitis (16/20) compared with control patients. The differences between these diagnostic groups and controls were highly significant (P less than 0.0001) and independent of pancreatic enzyme activity. Immunochemical analyses of serum pancreatic stone protein showed an isoelectric point (pH 9) similar to that reported for the pancreatic thread protein. With respect to recent communications, these data do not support the etiopathogenic role postulated for pancreatic stone protein in chronic pancreatitis and chronic calcifying pancreatitis by other investigators.     

Pancreatic stone protein: quantification in pancreatic juice by enzyme-linked immunosorbent assay and comparison with other methods

To quantitate pancreatic stone protein (PSP), a competitive radioimmunoassay using monoclonal antibodies to PSP extracted from pancreatic stones and a sandwich enzyme-linked immunosorbent assay (ELISA) using monospecific polyclonal antibodies to the secretory forms of PSP (PSP S) were established. When PSP concentrations were measured in pancreatic juice by radioimmunoassay, no difference could be found between patients suffering from chronic calcifying pancreatitis and other diagnostic groups. Yet, with the ELISA technique involving polyclonal antibodies, decreased concentrations were found in chronic calcifying pancreatitis patients when compared to controls (p less than 0.001), chronic alcoholics without pancreatic symptoms, or obstructive pancreatitis patients. These discrepancies are discussed. The monoclonal antibodies recognizing the C-terminal part of PSS S (PSP S1), results from the radioimmunoassay indicate that the concentration of that polypeptide is identical in the juice of controls and patients. Results from the ELISA obtained with polyclonal antibodies raised against PSP S2-5 molecules, i.e., recognizing the PSP S1 part and the N-terminal portion of the molecule, indicate that the differences observed reflect differences in the juice concentration of that N-terminal peptide.     

Protein content of precipitates present in pancreatic juice of alcoholic subjects and patients with chronic calcifying pancreatitis

Chronic calcifying pancreatitis is characterized by the formation of intraductal protein plugs or precipitates and calcified stones in ducts. Similar precipitates may be collected by endoscopic retrograde catheterization of the main pancreatic duct. They are present in the pancreatic juice of alcoholic subjects and patients with chronic calcifying pancreatitis. Protein analysis of these precipitates was performed to try to elucidate the mechanism of stone formation. Two protein fraction were separated by extraction of precipitates. One fraction was easily soluble in saline and contained a small amount of most of the proteins of pancreatic juice. The other fraction was soluble in citrate or ethylenediaminetetraacetate and contained a few proteins with close isoelectric points and identical molecular weight (13,500). These proteins showed immunological identity with the "stone protein" isolated from human pancreatic calculi. Our data demonstrate that the major citrate-soluble protein of precipitates in pancreatic juice is identical with "stone protein". They are strongly support the concept that this protein is the organic matrix of pancreatic stones. Different mechanisms are proposed to explain the phenomenon of protein precipitation that frequently occurs in alcoholic subjects and patients with chronic calcifying pancreatitis.     

Analysis of pancreatic stone protein gene of hereditary pancreatitis]

To investigate the pathogenesis of hereditary pancreatitis we determined whether pancreatic stone protein (PSP) gene was structurally altered in two independent families diagnosed as hereditary pancreatitis. Because, it has been shown that a decrease in the activity of PSP which inhibits CaCO3 crystal formation in pancreatic juice is closely related to the development of chronic calcifying pancreatitis. Southern blot analysis revealed neither a rearrangement nor a gross deletion of PSP gene in genomic DNA of affected members of both families. Furthermore, six exons of PSP gene amplified by polymerase chain reaction from genomic DNA was directly sequenced, while no apparent base mutation was observed. The immunohistochemical study utilizing monoclonal antibody to PSP showed the presence of immunoreactive PSP in the section of pancreatic tissue obtained from a patient affected with hereditary pancreatitis. However, the level of immunoreactive PSP in the remaining acinar cells of the patient pancreas was not reduced when compared with that of normal pancreas. Results, therefore, indicate that genetic alteration of PSP gene may not be responsible for the pathogenesis of hereditary pancreatitis.     

Idiopathic chronic calcifying pancreatitis with diabetes mellitus

Summary We present a case of a 27-year-old female suffering from chronic calcifying pancreatitis with diabetes mellitus. Radiographic examinations and exocrine pancreatic function tests revealed considerable dilatation of pancreatic ducts with large intraductal calculi and exocrine pancreatic insufficiency, respectively. Recent literature indicates that a decrease in the activity of pancreatic stone protein (PSP), which inhibits CaCO₃ crystal formation in pancreatic juice, is closely related to the development of chronic calcifying pancreatitis. The patient had no apparent cause or family history of pancreatitis. We therefore investigated the possibility that alterations in the PSP gene might explain the chronic pancreatitis seen in this patient. Six exons of the PSP gene amplified by polymerase chain reaction were directly sequenced, but there was no apparent base mutation observed. Furthermore, Southern blot analysis revealed neither rearrangement nor deletion of the PSP gene in the genomic DNA of this case. However, this genetic approach will be useful for future study of the etiology of hereditary pancreatitis.     

Immunocytochemical localization of pancreatic stone protein in the human digestive tract

Recently, in our laboratory, a protein extracted from human pancreatic stones was characterized and purified and a specific antibody was obtained. This pancreatic stone protein (PSP) was shown to have an inhibitory effect on the CaCO3 crystal growth in vitro. The cellular origin of such a protein and its repartition along the digestive tract were studied by immunolocalization (protein A-colloidal gold method) at the ultrastructural level. Surgical biopsies of pancreata from normal or chronic pancreatitis patients, needle liver biopsies, gastric mucosa, and jejunum and duodenum biopsies were minced and fixed in the Karnovsky medium or in buffered 4% paraformaldehyde. The specimens were washed in buffer, dehydrated through ethanol, and embedded in Epon 812. Ultrathin sections, collected on uncoated nickel grids, were submitted to the following reactives at room temperature: protein A 1 mg/ml, anti-PSP (1:2 to 1:100), and protein A-colloidal gold. The specificity of the localization was checked by substituting buffer or nonimmune rabbit serum to anti-PSP. The stone protein was markedly present in the zymogen granules and condensing vacuoles of the normal pancreatic acinar cells, the label was found in the acinar and ductal lumen. In chronic pancreatitis, the localization of PSP, when it occurred, was extremely weak in the acinar cells. No PSP was specifically characterized in hepatocytes, gastric mucosa, and enterocytes. However, a weak but specific reaction was found in the secretory granules of Paneth cells. These results in pancreas confirm the acinar secretory origin of the PSP and are in good agreement with its possible function in stabilizing pancreatic juice in vivo, which is normally supersaturated in calcium carbonate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Duodenal total and ionised calcium secretion in normal subjects, chronic alcoholics, and patients with various stages of chronic alcoholic pancreatitis.

Previous studies have shown increased secretion of total calcium in the duodenal juice of patients with chronic alcoholic pancreatitis compared with healthy subjects. In order to get more detailed information on calcium secretion and pancreatic stone formation in chronic alcoholic pancreatitis, ionised and total calcium concentrations were determined in the duodenal juice of normal subjects, chronic alcoholics, and patients with various stages of chronic alcoholic pancreatitis. Total calcium secretion was in agreement with previously published data. Chronic alcoholics presented a significant increase of ionised calcium. In the course of pancreatitis all calcium fractions increased progressively revealing highest concentrations in patients with severe exocrine insufficiency. In non-calcified and calcified pancreatitis all calcium fractions were identical. It is suggested that the increase of ionised calcium originates from serum ionised calcium passing by diffusion into the damaged pancreatic duct system.     

Lactoferrin and albumin in human pancreatic juice

Lactoferrin and albumin concentrations in pure pancreatic juice were studied by radial immunodiffusion in 81 patients. Lactoferrin concentration (% of total protein) was specifically increased in patients suffering from chronic calcifying pancreatitis (mean ±SE: 0.169±0.024) and no overlap was observed with patients suffering from other pancreatic diseases (0.008±0.001), organic nonpancreatic diseases (0.011±0.001) and without organic disease (0.01±0.001). Lactoferrin concentration was not found to be correlated with chronic alcohol consumption or pancreatic insufficiency. Albumin concentration (% of total protein) was increased in patients suffering from chronic calcifying pancreatitis (5.55±0.49) and other pancreatic diseases (5.45±1.02). These values were significantly higher (P<0.001) than the corresponding values in patients with organic nonpancreatic diseases (1.66±0.16) and patients without organic diseases (1.46±0.22). Measuring lactoferrin and albumin in pancreatic juice may aid in the diagnosis of pancreatic disease and in the differentiation of chronic calcifying pancreatitis, even in the earliest stage, from other pancreatic diseases such as pancreatic carcinoma or acute pancreatitis.     

Exocrine function of a heterotopically transplanted pancreas segment in humans

Pancreatic secretion is involved in circadian regulation of the whole organism. This observation was obtained in animals and humans with pancreatic fistulas. We report on three patients in whom the pancreas was removed totally or subtotally because of chronic pancreatitis with severe pain. A segment of the removed gland was transplanted into the thigh in order to preserve endocrine function. The pancreatic duct was drained by a polyethylene tube until pancreatic duct occlusion. Postoperatively juice volume increased within 3 days and remained constant afterwards with 300 ml in 24 hours. Secretin, cholecystokinin and food intake are able to stimulate the transplanted segment in a typical manner. The secretion showed circadian changes. In all patients the pancreatic juice content of protein, amylase, trypsinogen, calcium, and zink decreased till 11 p.m. After 11 p.m. the content of all substances increased and reached maximal values at 6 a.m. Flow rates and therefore output per minute decreased greatly till 6 a.m. The large juice volume of 300 ml in 24 hours is perhaps the consequence of a break down of the feedback mechanism between intraduodenal trypsin activity and CCK-release. The changes during the night may be of pathogenetic relevance. In the early morning pancreatic juice is highly concentrated and the flow rate is very low. High protein concentrations, high calcium concentrations, and reduced flow rates may lead to protein and calcium carbonate precipitates. This mechanism is under discussion in the pathogenesis of chronic pancreatitis.     

Organic matrix of pancreatic stones associated with nutritional pancreatitis

In recent studies performed on pancreatic stones from patients with alcoholic pancreatitis, a novel secretory protein was identified: the pancreatic stone protein (PSP Mr 14,000). This protein suppresses CaCO3 precipitation, and could therefore stabilize normally supersaturated pancreatic juice. Crystallographic analysis of stones from patients with nutritional pancreatitis (NP), as well as alcoholic pancreatitis (AP), revealed that the main constituent was calcite (CaCO3). In the present study, we investigated the organic matrix of NP stones. In the 14 cases studied, the organic matrix was rendered soluble after mineral dissolution with EDTA + citrate. Analysis of the isolated matrix revealed the presence of one major protein (Mr 14,000), and of a minor protein (Mr 30,000), which is in fact an aggregate form of the 14,000 Mr protein. Using PSP antibodies, complete immunological identity was found between PSP, the immunoreactive form of PSP present in nonactivated pancreatic juice, and the protein matrix of NP stones. Moreover, protein matrix of NP stones also inhibited the nucleation of CaCO3 crystal, and decreased their growth rate in vitro. The presence of PSP in all AP and NP stones suggests that it plays a key role in stone formation during the course of chronic pancreatitis. These results also suggest the existence of some pathophysiological links between these two apparently different etiological forms of calcifying pancreatitis.     

Purification and assay of secretory lithostathine in human pancreatic juice by fast protein liquid chromatography.

Impaired secretion of lithostathine, a pancreatic glycoprotein capable of inhibiting the growth of CaCO3 crystals, has been reported in chronic calcifying pancreatitis. Controversial results were obtained, however, using immunoassays with different antibodies. The aim of this study was to purify and to measure juice lithostathine by a non-immunological method. Fast protein liquid chromatography (FPLC) on a cation exchange column eluted by a sodium chloride gradient, was used. The conditions appropriate to separate secretory (S) from hydrolysed (H) isoforms of immunopurified lithostathine were also used for juice analysis. Pancreatic juice was collected by endoscopic cannulation of the major pancreatic duct, after secretin stimulation, from eight patients with chronic pancreatitis (CP) and from eight controls. In all samples, S-isoforms of lithostathine (ranging from 16 to 19 Mr at SDS-PAGE) were the only constituent of two of the 15 peaks in which FPLC resolved the pancreatic proteins. The nature of these two peaks was confirmed by their coelution with immunopurified S-lithostathine and by immunoblot analysis with polyclonal anti-lithostathine antibodies. The ratio between the area of S-lithostathine peaks and the total area of proteic eluates, was always lower in CP patients (5.3 micrograms/mg of protein, median value; 0.2-15.4, range) than in controls (35.2 micrograms/mg; 16.6-55.9). It is concluded that lithostathine can be purified and measured in pancreatic juice by FPLC. Our results with a nonimmunological assay confirm a reduced secretion of lithostathine in patients with CP.     

Pancreatic outflow obstruction as the critical event for human gall stone induced pancreatitis.

Opie suggested in 1901 that a common channel between the pancreatic duct and the common bile duct is created when a gall stone becomes impacted at the duodenal papilla. He proposed that bile would regurgitate into the pancreas and trigger pancreatitis. The case is reported of a 22 year old woman with an impacted stone at the duodenal papilla creating a common channel. The patient suffered from acute pancreatitis. Three days before the onset of pancreatitis, however, a T drain had been inserted into the common bile duct from which bile had been flowing freely and continuously. Moreover, amylase activity in fluid from the T drain was 49,000 U/l at the onset of pancreatitis pointing to reflux of pancreatic juice into the biliary tract. The amylase activity in bile decreased rapidly after endoscopic papillotomy and retrieval of the stone. The events participating in the development of acute gall stone induced pancreatitis in this patient with a common channel situation permitted reflux of pancreatic juice into the biliary tract rather than bile into the pancreas. Impairment of pancreatic outflow by a gall stone was probably the primary triggering event, rather than the regurgitation of bile into the pancreas. Preventive or therapeutic treatment in gall stone pancreatitis should be aimed at the urgent restoration of pancreatic flow rather than at the prevention of a hypothetical bile reflux.     

Persistence of the X-ray-transparent matrix of vanishing pancreatic stones

We present three observations of patients with chronic calcifying pancreatitis with multiple pancreatic calculi visible on X-ray films of the abdomen. These patients were studied with plain films and sonography. On X-ray films, visible calcifications disappeared. In contrast, sonography and computerized tomography showed that the X-ray-transparent material of stones persisted. It is known that these stones are composed of different insoluble residues of PSP-S2-5, the secretory calcium stabilizer of pancreatic juice. This shows that the spontaneous or drug-induced disappearance of pancreatic stones on radiologic films is not sufficient for healing chronic calcifying pancreatitis.     

Calcium concentration and artificial precipitates in human pancreatic juice

We studied the role of the increase in the calcium concentration in pure pancreatic juice of alcoholic noncalcified chronic pancreatitis. Pure pancreatic juice was obtained endoscopically. The pancreatic juice from patients with chronic pancreatitis was adjusted to pH 7.5; then the calcium concentration was adjusted to 0.4, 2.9, 5.4, or 10.4 mmol/L. Artificial precipitates were produced by incubation of the samples at 37 degrees C for 6 hours. Proteins in the artificial precipitates were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and the protein patterns were compared with the patterns of natural protein plugs from patients with chronic pancreatitis. The amount of the precipitate increased as the added calcium increased. The protein patterns of SDS-PAGE of the artificial precipitates were similar to those of protein plugs. Albumin, a-amylase, lipase, trypsinogen, and chymotrypsinogen were identified by immunoblotting both in the precipitate and in the protein plug. The increased calcium concentrations in pancreatic juice induced the formation of precipitates whose protein composition was similar to that of protein plugs. An increased calcium concentration in human pancreatic juice may play an important role in the pathogenesis of protein plugs.     

Regulation of PSP/reg in rat pancreas: immediate and steady-state adaptation to different diets.

Pancreatic stone protein/reg protein (PSP/reg) is a secretory pancreatic protein of hitherto unknown function. It is precursor to a spontaneously precipitating peptide called pancreatic thread protein, which is found in protein plugs within the pancreatic ductal system. Increasing PSP/reg concentrations in pancreatic juice might augment the risk of intraductal plug formation and therefore be a condition predisposing to chronic pancreatitis. Malnutrition is associated with a high incidence of chronic pancreatitis in tropical countries. In a diet study with rats, we tested the hypothesis that protein malnutrition leads to increased PSP/reg concentrations in pancreatic juice. A highly sensitive and reliable enzyme-linked immunosorbent assay (ELISA) for rat PSP/reg was newly established. Male Sprague-Dawley rats were allocated to three nearly isocaloric experimental diets, which contained 0, 45, or 82% casein, respectively, or to a control diet (22% casein). We evaluated PSP/reg expression under these four dietary conditions on the RNA and on the protein level, performing a time-course study over a period of 28 days. Our results demonstrate that PSP/reg expression is not increased because of a protein-deficient diet if investigated under steady-state conditions. After a temporary increase in PSP/reg levels due to a carbohydrate-deficient high-protein diet, we could not find signs of a diet-dependent regulation of this protein. The regulation of PSP/reg thus differs from that of most other pancreatic secretory proteins. Our findings contradict earlier reports that had drawn conclusions based solely on messenger RNA levels.     

Pancreatic intraductal sampling during ERCP in patients with chronic pancreatitis and pancreatic cancer: cytologic studies and k-ras-2 codon 12 molecular analysis in 47 cases.

BACKGROUND: A preoperative tissue diagnosis of pancreatic cancer is desirable but difficult to obtain. METHODS: Pancreatic brush cytology, salvage cytology, and collection of pancreatic juice were attempted prospectively during ERCP in 34 patients with pancreatic cancer and 11 with chronic pancreatitis. K-ras-2 codon 12 was analyzed for presence and type of point mutations. RESULTS: Brush cytology coupled with salvage cytology had a sensitivity of 74%. The addition of cytologic analysis of pancreatic juice did not substantially improve sensitivity (76%). K-ras-2 was mutated in both cancer (87%) and pancreatitis (40%). The specificity for cytology was 100% and for K-ras-2 mutations 60%. Combining cytology with mutation analysis increased sensitivity to 93% but reduced the positive predictive value. The negative predictive value never exceeded 75%. None of the patients with chronic pancreatitis had cancer develop (median follow-up 60 months). CONCLUSIONS: Pancreatic ductal brushing with salvage cytology is useful in the diagnosis of cancer, whereas cytologic analysis of pancreatic juice can be abandoned. At present, K-ras-2 mutation is not useful for differentiating pancreatic cancer from chronic pancreatitis or the identification of patients with chronic pancreatitis at risk for malignant transformation.     

Quantification of human lithostathine by high performance liquid chromatography.

Pancreatic stones of patients with chronic calcifying pancreatitis (CCP) are mostly made up of CaCO3 crystals. Formation and growth of such crystals is inhibited in vitro by lithostathine, a protein present in normal pancreatic juice. Decreased lithostathine activity was therefore suspected in patients with CCP, but comparison by immunoassay of lithostathine concentrations in the pancreatic juices of patients and controls led to conflicting results. This study shows that these discrepancies might have been caused in part by a remarkably high susceptibility of the protein to trypsin like cleavage, resulting in important structural changes and concomitant modifications of the epitopes. A novel lithostathine assay in juice was developed, based on separation of secretory proteins by high performance liquid chromatography. The chromatographic separation of lithostathine was based on hydrophobic interactions at pH 5.0 using a Phenyl-TSK column. This study showed with this assay that lithostathine concentrations (microgram/mg of total protein) were similar in CCP patients with alcoholic aetiology (mean (SD) 6.3 (2.7)) and other aetiologies (7.2 (3.7)), but one third of those estimated in patients without pancreatic disease (16.7 (4.3)). Similar concentrations were found, however, in chronic alcoholic patients without CCP (6.6 (3.3)) and in patients with CCP. It was concluded that decreased lithostathine concentration is associated with CCP, although such a decrease is not sufficient by itself for the disease to occur.     

Pancreatic juice gamma-glutamyltransferase,alanine transaminase,and alkaline phosphatase in pancreatic disease

Pancreatic juice gamma-glutamyltransferase (GGT, EC 2.3.2.2) has been proposed as a marker of pancreatic disease. We have collected pancreatic juice endoscopically from 24 control patients and 43 patients with a variety of hepatic, pancreatic, and biliary disorders. Pancreatic juice GGT, alanine transaminase (ALT, EC 2.6.1.2), and alkaline phosphatase (ALP, EC 3.1.3.1) were measured and found to be present in all samples. GGT was significantly higher in patients with pancreatic cancer (range 21–1175 IU/liter,P<0.005) compared with controls (range 2–52 IU/liter). Of 17 patients with pancreatic juice GGT concentrations greater than 52 IU/liter, eleven had definite pancreatic disease (seven pancreatic cancer, four chronic pancreatitis) and, in the remaining six, pancreatitis was possible although not proven. Pancreatic juice ALT and ALP provided no useful diagnostic criteria. GGT in pancreatic juice seems to be a nonspecific marker of pancreatic disease and merits further study.     

Identification of immunoreactive pancreatic stone protein in pancreatic stone, pancreatic tissue, and pancreatic juice

We first examined whether pancreatic stone protein (PSP) was present in pancreatic stone and normal pancreatic tissue. By using HPLC and Western blotting, a protein of Mr 13.5 kDa that reacted with monoclonal antibody against PSP was detected as a major component in EDTA-soluble fractions of pancreatic stone. In an in vitro experiment, this protein dose-dependently suppressed CaCO3 precipitation. PSP was immunohistochemically stained in the acinar cells of normal pancreatic tissue. Based on these findings, it seemed that PSP in pancreatic stone is probably a physiological secretory protein of the pancreas. We subsequently examined immunoreactive PSP in normal pancreatic juice by the Western blotting method. In all of the specimens, the band for immunoreactive PSP in pancreatic juice was found to correspond to 13.5 kDa, which thus agreed with that of purified PSP from a stone.