Studies on the mechanisms of biliary excretion of circulating glycoproteins. The carcinoembryonic antigen

Primary amyloidosis with increased plasma carcinoembryonic antigen concentration. A case report

A patient with suspected malignant disease had increased concentration of plasma carcinoembryonic antigen (CEA). Amyloidosis was demonstrated at autopsy. The amyloid fibril composition was characterized by immunohistochemical and immunochemical techniques and proved to be of the lambda light chain (AL) type. CEA was demonstrated in the liver parenchyma by using antihuman CEA antiserum. Increased plasma CEA concentration in a patient with primary amyloidosis has, to our knowledge, not been reported before.

Detection of occult liver metastases in colorectal cancer by measurement of biliary carcinoembryonic antigen concentration: A prospective study

BACKGROUND

It has been suggested that bile CEA levels could be a sensitive index for the detection of occult liver metastases (LM) in colorectal cancer (CRC) patients. The aim of this study was to determine the potential value of biliary CEA assay in the early detection of occult LM from CRC.

METHODS

From 1995 to 1999 biliary and blood CEA levels were determined in three groups of patients undergoing surgery; Group 1 (n = 35) patients with LM from CRC; Group 2 (n = 154) patients with CRC without LM; Group 3 (n = 23) was the control group.

RESULTS

Biliary and serum CEA levels were significantly lower in group 3 than in group 2 (P = 0.008 and P = 0.002) and in group 2 than in group 1 (P = 0.001 and P = 0.005). With a follow-up of 36 months (group 2), 22 patients (14%) developed LM. For 59 patients, the bile CEA level during laparotomy was less than 5 ng/ml and for 95 patients this level was more than 5 ng/ml, 4 and 18 patients respectively developed metachronous LM; we found a difference (P = 0.03) between these two subgroups. When this analysis was performed with regard to the stage of the tumor, we found no difference for the node negative cancer (n = 79) subgroup (P = 0.6), but we found a significant difference for the node positive cancer (n = 75) subgroup (P = 0.01).

CONCLUSIONS

Our data suggest that biliary CEA concentrations at the time of resection of the primary tumor cannot be used to identify patients with occult LM in the node-negative CCR subgroup. However, patients with node-positive CCR and bile CEA level under 5 ng/ml developed LM in only 3% of cases; it might be therefore, possible to use that as a discriminant in situations where the risk of LM is small.

Biliary carcinoembryonic antigen levels in diagnosis of occult hepatic metastases from colorectal carcinoma

AIM: To prospectively explore the role of carcinoembryonic antigen (CEA) in gallbladder bile in patients with colorectal carcinoma and the morphological and clinical features of neoplasia and the occurrence of hepatic metastases.

METHODS: CEA levels in the gallbladder and peripheral blood were studied in 44 patients with colorectal carcinoma and 10 patients with uncomplicated cholelithiasis. CEA samples were collected from the gallbladder bile and peripheral blood during the operation, immediately before extirpating the colorectal neoplasia or cholecystectomy. Values of up to 5 ng/mL were considered normal for bile and serum CEA.

RESULTS: In the 44 patients with colorectal carcinoma who underwent operation with curative intent, the average level of serum CEA was 8.5 ng/mL (range: 0.1 to 111.0 ng/ml) and for bile CEA it was 74.5 ng/mL (range: 0.2 to 571.0 ng/ml). In the patients with uncomplicated cholelithiasis who underwent cholecystectomy, the average level of serum CEA was 1.9 ng/mL (range: 1.0 to 3.5 ng/ml) and for bile CEA it was 1.2 ng/mL (range: 0.3 to 2.9 ng/ml). The average duration of follow-up time was 16.5 mo (range: 6 to 48 mo). Four patients who underwent extirpation of the colorectal carcinoma without evidence of hepatic metastasis and with an average bile CEA value of 213.2 ng/mL presented hepatic metastases between three and seventeen months after removal of the primary colorectal neoplasia. Three of them successfully underwent extirpation of the hepatic lesions.

CONCLUSION: High CEA levels in gallbladders of patients undergoing curative operation for colorectal carcinoma may indicate the presence of hepatic metastases. Such patients must be followed up with special attention to the diagnosis of such lesions.

Determinação do antígeno carcinoembrionário biliar na detecção das metástases hepáticas do carcinoma colorretal

OBJETIVO: Analisar, prospectivamente, os resultados da determinação do antígeno carcinoembriário (CEA) na bile vesicular, relacionando-os com os aspectos morfológicos e clínicos da neoplasia e recidiva hepática. MÉTODOS: Os níveis do CEA foram estudados na bile vesicular e no sangue periférico de 44 doentes com carcinoma colorretal e 10 com colelitíase não complicada, a partir de amostras do CEA colhidas imediatamente antes da extirpação da neoplasia colo-retal e da colecistectomia (considerou-se valor normal até 5 ng/ml). RESULTADOS: Os 44 carcinomas colorretais extirpados com intenção curativa tiveram nível médio do CEA sérico de 8,5 ng/ml e CEA biliar, 74,5 ng/ml. Nas colelitíases não complicadas submetidas a colecistectomia, o nível médio do CEA sérico foi de 1,9 ng/ml e CEA biliar, 1,2 ng/ml. Quatro doentes submetidos à extirpação do carcinoma colo-retal, sem evidências de metástases hepáticas e com valor médio de CEA biliar de 213,2 ng/ml apresentaram metástases hepáticas entre três a 17 meses após a extirpação. CONCLUSÃO: o nível elevado de CEA biliar dos operados por carcinoma colo-retal pode indicar presença de metástases hepáticas e esses enfermos devem ser acompanhados com especial atenção para diagnosticar essas lesões.

Value of CEA level determination in gallbladder bile in the diagnosis of liver metastases secondary to colorectal adenocarcinoma

CONTEXT

The relevance of colorectal adenocarcinoma lies in its high incidence, with the liver being the organ most frequently affected by distant metastases. Liver metastases occur in 40 to 50% of patients with colorectal adenocarcinoma, accounting for approximately 80% of deaths in the first three postoperative years. Nevertheless, despite this, they are occasionally susceptible to curative treatment.

OBJECTIVE

The present investigation focused on the relationship between the level of carcinoembryonic antigen (CEA) in gallbladder bile and the presence of liver metastases secondary to colorectal adenocarcinoma.

DESIGN

Diagnostic test study.

SETTING

Surgical Gastroenterology Discipline at the São Paulo Hospital, São Paulo, Brazil.

SAMPLE

Forty-five patients with colorectal adenocarcinoma were studied, 30 without liver metastases (group I), and 15 with liver metastases (group II). Diagnosis of liver metastases was made through computed tomography, magnetic resonance imaging and computed tomography during arterial portography. Samples of peripheral blood, portal system blood, and gallbladder bile were collected from patients during the surgical procedure. A control group composed of 18 organ donors underwent the same material collection procedures. CEA level determination was made through fluoroimmunoassay.

RESULTS

Mean CEA value in peripheral serum was 2.0 ng/ml (range: 0.7 to 3.8 ng/ml) in the control group, 11.4 ng/ml (range: 0.5 to 110.3 ng/ml) in group I, and 66.0 ng/ml (range: 2.1 to 670 ng/ml) in group II. In the portal system, serum mean values found were 1.9 ng/ml (range: 0.4 to 5.0 ng/ml) in the control group, 15.3 ng/ml (range: 0.8 to 133.3 ng/ml) in group I, and 70.8 ng/ml (range: 1.8 to 725 ng/ml) in group II. Mean values found in gallbladder bile were 4.1 ng/ml (range: 1.0 to 8.6 ng/ml) in the control group, 14.3 ng/ml (range: zero to 93.0 ng/ml) in group I, and 154.8 ng/ml (range: 14.0 to 534.7 ng/ml) in group II.

CONCLUSIONS

The CEA level in gallbladder bile is elevated in patients with liver metastases. Determination of CEA both in peripheral serum and in gallbladder bile enabled patients with liver metastases to be distinguished from those without such lesions. The level of CEA in gallbladder bile, however, seems to lead to a more accurate diagnosis of liver metastases secondary to colorectal adenocarcinoma.

Peribiliary capillary plexus around interlobular bile ducts in various chronic liver diseases: An immunohistochemical and morphometric study

Peribiliary capillary plexus (PCP) is a network of capillaries which arise from the hepatic artery surrounding the intrahepatic bile ducts. We immunohistochemically investigated the density of PCP around interlobular bile ducts in various chronic liver diseases including primary biliary cirrhosis (PBC) (n = 47), autoimmune hepatitis (AIH) (n = 12), chronic hepatitis B (n = 16), chronic hepatitis C (n = 19), liver cirrhosis due to hepatitis B virus (n = 13), liver cirrhosis due to hepatitis C virus (n = 20), alcoholic hepatitis (n = 20), alcoholic liver cirrhosis (n = 17), using human liver biopsies fixed in formalin and embedded in paraffin wax. PCP was immunohistochemically detected by an endothelial marker, the CD34 antigen. The number of PCP per duct was 1.21 +/- 0.18 in normal livers. Compared with normal liver, vasopenia was observed in PBC and AIH, the number in which was 0.93 +/- 0.34 (P < 0.0001) and 0.82 +/- 0.38 (P < 0.005) per duct, respectively. In contrast, increased number of PCP was observed in liver cirrhosis due to hepatitis B or C virus, alcoholic hepatitis, and alcoholic liver cirrhosis, the number in which were 1.59 +/- 0.37 (P < 0.005), 1.55 +/- 0.52 (P < 0. 02), 1.38 +/- 0.23 (P < 0.02) and 1.61 +/- 0.33 (P < 0.002) per duct, respectively. These data suggest that PCP may be destroyed in autoimmune liver diseases, including PBC and AIH, but PCP may proliferate in other inflammatory and alcoholic liver diseases.

Liver uptake and hepato-biliary transfer of galactosylated proteins in rats are determined by the extent of galactosylation

The effect of molecular mass and surface density of galactose residues on hepatic uptake and subsequent biliary excretion of galactosylated proteins was investigated in rats. Several proteins with different molecular weights (15-70 kDa) and different numbers of galactose units were synthesized and radiolabeled with 111In. Galactosylated proteins were administered i.v. to anaesthetized rats and samples of plasma and bile were collected for 3 h. Liver was harvested at the end of the experiments and the radioactivity of all samples was measured. Galactosylated proteins accumulated primarily in the liver and 2-10% of the administered dose appeared in the bile, mainly in undegraded form. The hepatic uptake clearance (Cl liver) and biliary excretion rate constant (kbile) of galactosylated proteins were calculated. No direct effect of molecular weight was observed, however, on increasing the galactose density, Cl liver increased from about 4 to 400 ml/h whereas kbile gradually decreased from about 0.057 to 0.007 (h-1). In conclusion, both hepatic uptake and biliary excretion of galactosylated proteins were found to be affected by the extent of galactosylation.

The use of biliary CEA measurements in the diagnosis of recurrent colorectal cancer

To assess the usefulness of biliary CEA determinations in the diagnosis of recurrent tumour, gallbladder bile was sampled in patients who underwent laparotomy for proven or suspected recurrent colorectal cancer and in control patients. Biliary CEA concentrations in controls were < 5 ng/ml, whereas significantly elevated CEA concentrations were found in the bile of all patients with tumour recurrence. Serum concentrations in these patients were elevated in 77% only. In a series of 12 patients with (a) suspicious lesion(s) on liver imaging but normal serum CEA concentration during follow-up, biliary CEA determination differentiated clearly between metastases and benign lesions. Biliary CEA determination seems to aid detection of tumour recurrence at an early stage and may preclude unnecessary surgery in patients with undefined liver lesions.

Ultrastructural and immunohistochemical studies of the intrahepatic peribiliary capillary plexus in normal livers and extrahepatic biliary obstruction in human beings

Ultrastructural and immunohistochemical study was conducted on the intrahepatic peribiliary capillary plexus in normal livers and in those with extrahepatic biliary obstruction. In both conditions, capillaries positive for Ulex europaeus agglutinin I and type IV collagen were always present in the vicinity of the bile ducts. Immunoelectron microscopy showed the presence of type IV collagen on the basal lamina of these capillaries; Ulex europaeus agglutinin I was also positive on their cytoplasms. Under electron microscope, a considerable number of these capillaries were seen as being composed of fenestrated endothelium with a diaphragm and with extreme cytoplasmic attenuations that were dense at the sides facing the bile duct in comparison with the opposite sides in normal livers. In extrahepatic biliary obstruction, plasmalemmal pinocytic vesicles, multivesicular bodies and other cellular organellae such as rough endoplasmic reticulum and Weibel-Palade bodies increased in number in these capillaries, relative to normal livers, probably reflecting increased permeability and functional activities. These characteristic ultrastructural features of the peribiliary capillary plexus might be arranged to transport substances effectively by way of intrahepatic biliary epithelial cells in normal livers and also might be altered to meet the increased functional demands of extrahepatic biliary obstruction.

Morphologic demonstration of receptor-mediated endocytosis of epidermal growth factor by isolated bile duct epithelial cells

It was recently shown that intrahepatic bile duct epithelial cells in situ or after isolation from rat liver have coated pits and vesicles, suggesting that they participate in receptor-mediated endocytosis. Therefore, using a morphologic approach and epidermal growth factor coupled to horseradish peroxidase or colloidal gold as probes, we studied freshly isolated or short-term cultured intrahepatic bile duct epithelial cells prepared from normal rat liver to determine if they participate in receptor-mediated endocytosis. Immunoelectron microscopy using a monoclonal antibody against the epidermal growth factor receptor was also used to examine for the presence of the growth factor receptor on the cells. Immediately after isolation, the cells did not internalize either epidermal growth factor-horseradish peroxidase or epidermal growth factor-colloidal gold; no growth factor receptor could be shown on these cells by immunocytochemistry, either. In contrast, cells cultured for 24 h bound and internalized both epidermal growth factor-horseradish peroxidase and epidermal growth factor-colloidal gold at 37 degrees C and showed growth factor receptors diffusely distributed on the plasma membrane. When cultured cells exposed to epidermal growth factor-colloidal gold were fixed with glutaraldehyde containing saponin and tannic acid, colloidal gold particles were observed in coated pits and in coated and uncoated vesicles. Preincubation of cultured cells with native epidermal growth factor completely blocked the internalization of both epidermal growth factor-horseradish peroxidase and epidermal growth factor-colloidal gold. When rat liver was stained in situ for epidermal growth factor receptor, reaction product was observed by immunoelectron microscopy exclusively on the basal surface of the plasma membrane of the intrahepatic bile duct epithelial cells. These results indicate that bile duct epithelial cells internalize epidermal growth factor by endocytosis via coated pits containing receptors localized in situ exclusively to the basal domain of their plasma membranes. The data demonstrate for the first time that intrahepatic bile duct epithelial cells participate in receptor-mediated endocytosis and raise the possibility that they are a target for epidermal growth factor.

Relationship between colorectal liver metastases and CEA levels in gallbladder bile

While computerized tomographic (CT) scanning and intraoperative exploration are both considered accurate measures of liver involvement with metastatic disease, 10% to 30% of colorectal liver metastases remain undetected. Attempting to improve current methods for detecting colorectal liver metastases, CEA levels in gallbladder bile and serum from patients with known liver metastases were determined. One hundred per cent of patients with single and multiple metastases of various dimensions were observed to have gallbladder bile CEA levels strikingly higher than serum values (4.7 to 259 times greater, p = 0.0009). Linear regression analysis of estimated tumor volume and surface area versus gallbladder bile CEA levels predicted that very small tumors (less than or equal to 1 cm3 in volume) might produce detectable levels (9 to 41 ng/mL) of biliary CEA. For this reason, patients who lack clinical and radiologic evidence of distant metastases at the time of primary colorectal resection but who do have elevated gallbladder bile CEA levels (greater than or equal to 10 ng/mL) are being followed for the appearance of occult hepatic metastases.

Hepatic clearance and metabolism in the rat of a human breast cancer associated glycoprotein (GCDFP-15)

Gross Cystic Disease Fluid Protein (GCDFP-15) is a 60,000 dalton glycoprotein isolated from human breast cyst fluid, composed of four 15,000 dalton monomers. Carbohydrate analysis indicates that each monomer has a single carbohydrate chain of the complex type. GCDFP-15 intravenously injected into rats showed a rapid circulatory clearance, the rate of clearance being faster in female animals [t1/2 = 12.8 (+/- 2.0) min. females, and 16.7 (+/- 2.6) min. males]. The major organs of clearance were the liver (70%) and kidneys (15%). Immunoperoxidase staining showed localization in Kupffer cells and the proximal convoluted tubules of the kidney. Removal of sialic acid from GCDFP-15 resulted in a more rapid clearance (t1/2 = 2.2 min) by the liver (85%). This clearance was inhibited by coinjection of asialo alpha 1 acid glycoprotein. About 3% of GCDFP-15 was excreted in bile with a transit time through the liver of 38 min. Examination of the uptake of GCDFP-15 by isolated rat Kupffer cells showed that yeast mannan, fucosylated BSA, and carcinoembryonic antigen (CEA) failed to inhibit uptake, though the binding of GCDFP-15 was clearly saturable. This suggests that a novel receptor system on the rat Kupffer cell may be responsible for GCDFP-15 clearance.

Binding, uptake, and transcytosis of ligands for mannose-specific receptors in rat liver: an electron microscopic study

We have investigated the initial distribution of mannose-specific binding sites in rat liver as well as the uptake and transcytosis pathways of ligands for this receptor in in situ and in vivo experiments. As ligands we used mannan adsorbed onto colloidal gold particles of sizes 5, 17, and 35 nm (Man-Au5, Man-Au17, or Man-Au35). The in situ binding pattern of Man-Au5 in the prefixed liver is identical to the one described earlier for galactose-exposing ligands in the same organ. With the exception of the binding by hepatocytes, where only scarce binding of Man-Au5 was observed, ligands were found adhering in a preclustered pattern all over the cell surface of liver macrophages and binding in aggregates over the coated pits of endothelial cells. In double-labeling experiments different particle sizes were used for glycoproteins with terminal mannosyl or galactosyl residues. This simultaneous localization of the two binding activities revealed that on endothelial cells the two activities are always found to be present in the same coated pit. On liver macrophages the clustered binding occurred at different membrane areas. Uptake and transcytosis of Man-Au5, 17, 35 were studied after their injection into the tail vein. Three and fifteen minutes after injection most of the Man-Au5 and all of Man-Au17 or Man-Au35 was found in sinusoidal liver cells, i.e., macrophages and endothelial cells. One hour after injection, endocytosed ligand is redistributed from large--presumably lysosomal--vacuoles to small noncoated vesicles that are localized predominantly near the space of Dissé. Between 1 and 40 h after injection, ligands of all sizes are transcytosed and found in the hepatocytes. No ligand accumulation is observed in hepatocytes as an indirect indication for secretion into bile. With this investigation we give evidence for transcytotic activity not only of liver endothelium but also of the resident liver macrophages.

Carcinoembryonic antigen, CA 19-9, and CA 125 in normal and carcinomatous human colorectal tissue

In 115 primary colorectal carcinomas and 64 normal colorectal mucosa specimens the concentrations of carcinoembryonic antigen (CEA), CA 19-9, and CA 125 were measured. The determinations were performed in cytosols by use of radioimmunometric and enzymeimmunometric assays and related to the wet tissue weight. In the cancer tissue the CEA levels ranged from 5.5 to 1990 micrograms/g tissue and were significantly higher (P less than 0.0001) than those found in the normal mucosa (1.2-58.6 micrograms/g). The CA 19-9 content in carcinoma specimens (120-72660 U/g) was also significantly higher (P = 0.011) than in the normal mucosa (37-5800 U/g). In contrast, no significant difference of the CA 125 concentrations between the normal and the cancer tissue was found. The relative operating characteristic (ROC) curves for the three markers corroborate CEA as the marker superior to CA 19-9. On the other hand is shown that CA 125 is completely unable to discriminate between normal and cancer tissues. A decreasing CEA tissue concentration and an increasing dedifferentiation of colorectal cancers were significantly (P = 0.018) related with each other. Higher tumor stages implied significantly higher tissue marker values of CA 19-9 (P = 0.027) and CA 125 (P = 0.0008). The findings correspond quite well with serum examinations of the three markers which have been reported earlier.

Receptor-mediated endocytosis of enterokinase by rat liver. Preliminary characterisation of low-density endosomes

The endocytosis of enterokinase by rat hepatocytes has been studied both in a perfused liver system and in the intact, anaesthetised animal. 10 min after administration of the enzyme, only 70% of the activity was cleared by the perfused liver, whereas clearance was total in the intact animal. In both cases, about 85% of the internalised enzyme co-purified with the smooth microsomes and virtually all (more than 90%) of the catalytic activity was latent and could only be detected in the presence of detergent. After 10 min, 22.5% of the activity remained with the sinusoidal plasma membrane in the case of the perfused liver, while for the intact animal this figure was only 10%, confirming the more efficient clearance of enterokinase in the intact animal. Further subcellular fractionation showed that in the anaesthetised animal 8% of the internalised enzyme was associated with a low-density Golgi-like endosomal compartment (prepared from the mitochondrial pellet), whereas the corresponding value for the perfused liver was only 2.5%. Enterokinase specific activity was also up to 50-times greater in the low-density endosomes prepared from the intact animal. A second low-density Golgi-like compartment (purified from the smooth microsomes) also contained latent enterokinase, which together with the endosomes derived from the mitochondria accounted for 20% of the total enterokinase internalised by the liver 10 min after its administration to the intact animal. The passage of enterokinase through these two low-density compartments was shown not to be synchronous with its passage through the peripheral (sinusoidal membrane) and internal endosomes (smooth microsomes). There were qualitative differences in marker enzymes and polypeptide composition between the mitochondria and microsome-derived low-density endosomes. The sub-fractionation of low-density fractions on shallow sucrose gradients revealed a complex enzyme and polypeptide heterogeneity both between and within fractions. There was an apparent density-dependent separation of enterokinase from galactosyltransferase and the asialoglycoprotein receptor which was coincident with marked changes in the polypeptide composition of the endosomal membranes, particularly in the 30-45 kDa range.

Uptake and processing of glycoproteins by rat hepatic mannose receptor

A linear compartmental model has been developed for the in vivo metabolism of glycoproteins. The model is applied to the interpretation of dynamic data from the rat on agalactoorosomucoid (AGOR), an N-acetylglucosamine (GlcNAc-)-terminated glycoprotein, and three neoglycoproteins terminating in mannose [mannose36-bovine serum albumin (Man-BSA)] or glucose [maltose29-BSA (Mal29-BSA) and maltose8-BSA (Mal8-BSA)]. All of these proteins are taken up by the Man/GlcNAc receptor on hepatic sinusoidal cells. The rate of uptake was found to be determined by sugar type (Man-BSA, 0.78 min-1 greater than Mal29-BSA, 0.13 min-1), sugar density (Mal29-BSA greater than Mal8-BSA), and the geometry of the sugar display (AGOR, 0.51 min-1 greater than Mal29-BSA). Intracellular transport from the cell membrane to the lysosomes was slower for Man-BSA (approximately 3 min) than for the other ligands (approximately 0 min), suggesting that receptor-ligand uncoupling was slower for Man-BSA for which the receptor had the highest affinity or that extralysosomal catabolism of the other ligands occurred. Catabolism was also determined by the carbohydrate moiety of the ligand; it was greater for Mal29-BSA and Mal8-BSA (greater than or equal to 0.8 min-1) than for Man-BSA (0.27 min-1), and AGOR, with a complex oligosaccharide, was most resistant to degradation (0.14 min-1). An understanding of these structural features of glycoproteins that influence hepatic uptake, transport, and catabolism will be of value in drug targeting and for enzyme replacement in lysosomal storage disorders.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Naphthylisothiocyanate-induced permeability of hepatic tight junctions to proteins

We have studied the early action of 1-naphthylisothiocyanate (ANIT) in relation to its effect on the permeability barrier formed by hepatic tight junctions. Materials having different Mr values [inulin (5000), horseradish peroxidase (HRP) (40,000), ovalbumin (also 40,000) and pig gamma-globulin (IgG) (160,000)] were individually pulsed, within 1 min, into perfused rat livers operating under single-pass conditions. In untreated rats, a small peak of HRP and ovalbumin and a comparatively larger peak of inulin were observed in the bile at 7 min. In rats treated with ANIT, with increasing duration of ANIT treatment the inulin peak increased proportionally, whereas the HRP and ovalbumin peaks remained unchanged until after 10 h of ANIT exposure; gamma-globulin was not detected in the 7 min bile sample until after 14 h of ANIT treatment. Bile flow in all rats remained approximately the same until after 14 h of ANIT pretreatment, when substantial bile-flow reduction was observed. Phenobarbitone pretreatment increased the effect of ANIT and massively elevated the first HRP peak; it also shortened the time (to 4 h) at which the increase in permeability to this protein was observed. In contrast, the first HRP peak was virtually abolished in rats that had received the mixed-function-oxidase inhibitor SKF 525A. These experiments suggest that (i) ANIT progressively increased the permeability of the junctional barrier before the reduction in bile flow, (ii) the ANIT-increased permeability change seems to be inversely dependent upon the Mr of the infused proteins, and (iii) metabolites of ANIT were involved in the development of the junctional permeability change.

Phospholipid degradation in, and protein content of, rat fistula bile. Contamination of bile with pancreatic juice

The extent to which pancreatic juice can contaminate bile collected from a rat with a biliary fistula has been investigated by cannulating the bile duct proximal to either the duodenum or the liver, and by stimulating pancreatic flow with secretin. Bile collected via a fistula proximal to the duodenum showed marked pancreatic contamination. Thus, bile collected via a fistula proximal to the duodenum has a higher flow rate, a greater total protein and amylase content and a different polypeptide profile than bile collected via a fistula proximal to the liver. The phospholipid content also differed in that phosphatidylcholine was converted enzymically to lysophosphatidylcholine. Secretin increased bile flow and the biliary output of total protein and amylase when the fistula was proximal to the duodenum, but had no effect upon these parameters when the fistula was proximal to the liver, or in the isolated perfused rat liver.

Transcytosis and paracellular movements of horseradish peroxidase across liver parenchymal tissue from blood to bile. Effects of alpha-naphthylisothiocyanate and colchicine

The pathways for the entry of horseradish peroxidase (HRP) into bile have been investigated using the isolated perfused rat liver operating under one-pass conditions. Following a 1 min one-pass infusion of HRP, two peaks of HRP activity were noted in the bile. The first, at 5-7 min post-infusion, correlated with the biliary secretion of the [3H]methoxyinulin which was infused simultaneously with the HRP. The second peak of HRP activity occurred at 20-25 min, and correlated with the biliary secretion of 125I-IgA, which was also infused simultaneously with the HRP. If the isolated livers were perfused with a medium containing 2.5 microM-colchicine, the biliary secretion of IgA and the second secretion peak of HRP were inhibited by 60%. If rats were pretreated for 12h with alpha-naphthylisothiocyanate (25mg/100g body wt.) prior to liver isolation, the biliary secretion of [3H]methoxyinulin and the first secretion peak of HRP were increased. Taken together, these results suggest that HRP enters the bile via two routes. The faster route, which was increased by alpha-naphthylisothiocyanate and correlated with [3H]methoxyinulin entry into bile, was probably paracellular, involving diffusion across tight junctions. The slower route, which was inhibited by colchicine and correlated with the secretion of IgA, was probably due to transcytosis, possibly within IgA and other transport vesicles.

Fibrolamellar carcinoma of the liver. Review of three cases and the presentation of a characteristic set of tumor markers defining this tumor

This study demonstrates the unique clinical and histologic aspects of fibrolamellar hepatic carcinoma, a rare variant of hepatocellular carcinoma. Three cases are reviewed and an extensive study of immunologic and intracellular substances defining this tumor is presented. Length of survival was considerably longer than typical hepatoma. The cause of death generally is due to a lack of control of the primary tumor. Successful treatment appears to relate to the ability to perform a total excision of the primary hepatic tumor. Chemotherapy should be used only in the presence of metastatic disease. Surgical resection of metastatic disease, unlike the usual hepatocarcinoma, may have some beneficial use. Fibrinogen was found in all tumors. It is possible that this tumor produces fibrinogen to create its unique histologic appearance. Carcinoembryonic antigen is described for the first time in this tumor. Both deposits of alpha-1 antitrypsin and copper were found in most of the tissues studied. The presence and amounts of these substances differ markedly from the common type of hepatoma. This unique composition of intracellular components may both facilitate histologic diagnosis, particularly if the amount of tissue is limited, and give further insight into the etiology of this tumor.

The effects of colchicine and vinblastine on the biliary excretion of carcinoembryonic antigen

The biliary output of carcinoembryonic antigen (CEA) in bile fistula rats following treatment with the microtubule poisons vinblastine and colchicine increased 3-fold over a 4-hr period. Cytochalasin B and the inactive colchicine derivative lumicolchicine had no effect. These treatments did not effect the rate of CEA clearance from the circulation. Biliary output of low molecular weight fragments from CEA degradation was decreased in the presence of colchicine and vinblastine. Mechanical obstruction of the bile duct for 3 days followed by relief of obstruction resulted in a 3-fold increased output of CEA into the bile. These results are consistent with a paracellular mechanism for CEA transport from blood to bile. Biliary duct obstruction and vinblastine and colchicine probably affect the permeability of junctional complexes between hepatocytes allowing CEA to penetrate more easily.

Biliary proteins

The study of biliary proteins has grown enormously in the last 10 years. Although much has been recently learned about the nature, origin and hepatobiliary transport of these proteins, little is known of their function in bile or their effect on its physical state. This review will focus on description of the proteins and mechanisms by which they are secreted into bile.

Origins of biliary copper

We tested the hypothesis that the copper present in bile--the major route of elimination of the metal from the body--is derived exclusively from hepatocytes by administering radiocopper (64Cu or 67Cu)-labeled ionic Cu, desialylated (AsCPN) or intact human ceruloplasmin (CPN), intravenously, to rats with cannulated bile ducts. The rates of appearance and the total amounts of radiolabeled isotope recovered in bile were measured. The three vehicles chosen for the delivery of radiocopper interact differently with hepatocytes: ionic Cu is taken up by a passive process (Schmitt, R. C. et al., Am. J. Physiol. 1983; 244:G183-G191); AsCPN is promptly cleared from the circulation by specific receptor-mediated endocytosis, and CPN largely remains in the circulation for the duration of the experiment. Similar amounts of radiocopper were recovered following injections of ionic Cu (3.1%) or CPN (2%), but substantially larger amounts (8.1%) were excreted after administration of AsCPN. Using an antibody to CPN which reacts also with AsCPN, we found about 70% of the bile radioactivity to be immunoprecipitable following injections of either glycoprotein, indicating that a fraction of these copper proteins had entered the bile essentially unmodified. Our observations indicate that in addition to the lysosomal compartment which catabolizes a portion of the AsCPN in hepatocytes, there appears to be a direct route for AsCPN from hepatocellular sinusoids to the bile canaliculi. Since CPN does not interact significantly with hepatocytes, its presence in bile suggests transcytosis via the biliary epithelium.

Receptor-mediated biliary transport of immunoglobulin A and asialoglycoprotein: sorting and missorting of ligands revealed by two radiolabeling methods

In the rat, all receptor-bindable immunoglobulin A (IgA), and 1-4% of injected asialoglycoprotein (ASG), are transported from blood to bile intact. The major fraction of the ASG is degraded in hepatic lysosomes. The study described here was designed to elucidate the sorting that occurs in hepatocytes subsequent to receptor binding of ligands not sharing the same fate. We show that conjugation of protein with the Bolton and Hunter reagent can be used as a probe for the lysosomal pathway, since 50% of the reagent is released into bile after lysosomal degradation of internalized protein. Radiolabeling by iodine monochloride was alternatively used to follow the direct pathways that deliver intact IgA and ASG to bile. After intravenous injection of labeled proteins, first intact ASG and IgA, and then radioactive catabolites from degraded protein, were released into bile. No proteolytic intermediates were detected, and the transport of IgA or ASG directly to bile was not affected by the lysosomal protease inhibitor leupeptin. These observations indicate that divergence of the direct biliary transport pathways from the degradation pathway occurs at a stage preceding delivery to lysosomes, possibly at the cell surface. Competition studies showed that all three pathways (including the biliary transport of intact ASG) are receptor mediated, but even at supersaturating doses the uptake and processing of IgA and ASG occur independently. We propose that IgA and ASG receptors are not frequently in juxtaposition on the plasma membrane, but that ASG, after binding to its receptor, is occasionally missorted into the biliary transport pool.

Abnormal secretion of proteins into bile from colchicine-treated isolated perfused rat livers

The microtubule poison, colchicine, caused an abnormal output of a variety of proteins into rat bile. After 3 h of exposure to the drug, livers were isolated and perfused with media of defined protein composition. There was no essential change in permeability of the hepatobiliary system to proteins (e.g. bovine serum albumin) entering bile from the perfusion fluid. The rat (serum) albumin and fibrinogen that were secreted into bile from colchicine-treated livers were probably derived from the hepatocytes. Disruption of the microtubular system reduces the secretion of proteins at the sinusoidal face of the hepatocyte and results in an accumulation of secretory vesicles in the cytoplasm. It is suggested that under these conditions some of the vesicles discharge their contents into the bile canaliculus.

Immunocytochemical staining for CEA in small cell carcinoma of lung predicts clinical usefulness of the plasma assay

Recent studies have shown plasma CEA levels are useful in both staging and monitoring response to treatment in patients with small cell cancer of the lung (SCCL). CEA elevations do not occur in all patients however, and have been of less value in patients with limited disease. Immunoperoxidase staining for CEA performed on tumor tissue from 48 patients (17 extensive, 31 limited disease) with SCCL revealed: (1) A strong correlation between positive CEA tissue staining and plasma CEA elevation. Plasma CEA elevations occurred in 18/21 CEA tissue positive patients and correlated with the clinical course in all 18. In contrast elevated plasma CEAs were seen in only 3/27 CEA tissue negative patients; (2) CEA tissue positive patients had a higher incidence of extensive disease (62% versus 18%) and a higher incidence of liver metastases (43% versus 7%); and (3) No correlation between histologic subtype and CEA tissue staining was apparent.

Role of the liver in clearance and excretion of circulating carcinoembryonic antigen (CEA)

CEA is a glycoprotein with a molecular weight of 200,000 containing 55%-65% carbohydrate. The removal of only two sialic acid residues result in rapid uptake from the circulation by the liver and catabolism in the lysosomes. There is a receptor on the plasma membrane of the hepatocyte (hepatic binding protein) which recognizes galactosyl residues. About 70% of 125I-labeled intact CEA is cleared by the liver in 1 hr. The exposure of terminal galactose residues by removing sialic acids determines the rate of clearance. CEA is probably initially taken up by Kupffer cells and transferred to hepatocytes. About 10% of CEA added to an isolated perfused liver appears in bile. Biliary duct obstruction and cholestasis may elevate plasma CEA levels due to detergent effects on the liver cell receptors.

Biliary protein output by isolated perfused rat livers. Effects of bile salts

The output of proteins into bile was studied by using isolated perfused rat livers. Replacement of rat blood with defined perfusion media deprived the liver of rat serum proteins (albumin, immunoglobulin A) and resulted in a rapid decline in the amounts of these proteins in bile. When bovine serum albumin was incorporated into the perfusion medium it appeared in bile within 20 min and the amount in the bile was determined by the concentration of the protein in the perfusion medium. The use of a defined perfusion medium also deprived the livers of bile salts and the amounts of these, and of plasma-membrane enzymes [5'-nucleotidase (EC 3.1.3.5) and phosphodiesterase I], in bile declined rapidly. Introduction of micelle-forming bile salts (taurocholate or glycodeoxycholate) to the perfusion medium 80 min after liver isolation markedly increased the output of plasma-membrane enzymes but had no effect on the other proteins. The magnitude of this response was dependent on the bile salt used and its concentration in bile; there was little effect on plasma-membrane enzyme output until the critical micellar concentration of the bile salt had been exceeded in the bile. A bile salt analogue, taurodehydrocholate, which does not form micelles, did not produce the enhanced output of plasma-membrane enzymes. This work supports the view that the output of plasma-membrane enzymes in bile is a consequence of bile salt output and also provides evidence for mechanisms by which serum proteins enter the bile.

Biliary excretion of enterokinase in rats: studies in alcoholic rats with fatty liver

Ethanol-associated fatty liver was induced in rats fed a nutritionally deficient liquid diet containing 36% of total calories as ethanol. Control rats received the same diet with sucrose substituted isocalorically for ethanol. After 40 days, hepatic lipid content of the ethanol-maintained animals was four-fold greater than controls and ultrastructural changes in hepatocytes were well established. Clearance of intravenously administered human enterokinase from the circulation as well as bile flow were, however, the same in both groups. The proportion of enterokinase appearing in catalytically active form in bile after intravenous injection was substantially greater in the ethanol-maintained animals than the isocaloric controls; the difference was highly significant (p less than 0.001) and reached two- to four-fold after 70 days on the diet. These findings would suggest that the ability of hepatocytes to degrade enterokinase cleared from the blood may be bypassed or impaired by prolonged ethanol consumption and a deficient diet. Catalytically active enterokinase in bile may participate in the development of some types of acute necrotising pancreatitis.

The mechanism of biliary excretion of alpha 1-acid glycoprotein in the rat: evidence for a molecular weight-dependent, nonreceptor-mediated pathway

The transport of human alpha 1-acid glycoprotein from the circulation to the bile has been studied in the rat. Biliary excretion was proportional to the i.v. injected dose, and the percentage excreted remained constant. The amount excreted in the bile (over 4 hr) was inversely related to the rate of hepatic (hepatocyte) uptake and the galactose receptor which is specific for asialo glycoproteins was not involved. Reinjection of the glycoprotein excreted in bile resulted in a similar proportion of the dose being reexcreted, suggesting that a subset of the glycoprotein is not selected for excretion in bile. Transit times from blood to bile for glucagon, insulin, alpha 1-acid glycoprotein, fetuin, albumin, and carcinoembryonic antigen were directly related to their molecular weights. Removal of sialic acid from the asialo glycoproteins did not affect these transit times. Possible mechanisms for the biliary excretion of alpha 1-acid glycoprotein are discussed.

A new Kupffer cell receptor mediating plasma clearance of carcinoembryonic antigen by the rat

Native human carcinoembryonic antigen is rapidly removed from the circulation by the rat liver Kupffer cell after intravenous injection. The molecule is subsequently transferred to the hepatocyte in an immunologically identifiable form. Carcinoembryonic antigen has a circulatory half-life of 3.7 (+/- 0.8) min, and cellular entry is by receptor-mediated endocytosis. Non-specific fluid pinocytosis and phagocytosis can be excluded as possible mechanisms by the kinetics of clearance and failure of colloidal carbon to inhibit uptake. Substances with known affinity for the hepatic receptors for mannose, N-acetylglucosamine, fucose and galactose all fail to inhibit carcinoembryonic antigen clearance. After two cycles of the Smith degradation, carcinoembryonic antigen is still able to inhibit clearance of the native molecule. Receptor specificity is apparently not dependent on those non-reducing terminal sugars of the native molecule. Performic acid-oxidized carcinoembryonic antigen also inhibits clearance of carcinoembryonic antigen in vivo. Receptor binding is not dependent on tertiary protein conformation. Non-specific cross-reacting antigen, a glycoprotein structurally similar to carcinoembryonic antigen, is cleared by the same mechanism.

Circulating CEA levels in patients with fulminant hepatitis

CEA levels were determined in blood specimens from 14 persons suffering from fulminant hepatitis. Values ranged from 1.9 to 21 ng/ml with a mean of 7.0 ng/ml. All except one patient had a CEA level greater than 2.5 ng/ml, but only three exceeded 10 ng/ml. There was no correlation between single CEA levels and prognosis, routine liver chemistries, or histopathologic characterization of hepatic tissue obtained at postmortem examination. These data show that patients with fulminant hepatitis commonly had increased circulating levels of CEA, but these elevations were far less than may be found in patients with hepatic metastases. In severe hepatic dysfunction reduced hepatic clearance of CEA may be responsible for the increased levels.

The biliary excretion of enterokinase in rats. Studies in normal, chronic ethanol-maintained and cirrhotic rats

The excretion of catalytically active human or pig enterokinase in hepatic bile after intravenous administration to normal rats or rats that had been maintained on 20% (v/v) ethanol for 1 year showed similar kinetics to that described for other serum-derived bile proteins. The half-life in serum was 2.5 min or less, and most of the enzyme was excreted within 45 min of administration. This was maintained when up to six successive doses were given at 90 min intervals. The mean amount excreted per dose was independent of the dose number and varied from 0.8% to 2.1% in the normal animals and 1.2% to 2.0% in the chronic ethanol-maintained animals. When three doses of enzyme were given at 30 min intervals, the total amount of active enterokinase recovered in bile was dose-dependent and was consistently higher in the rats drinking 20% (v/v) ethanol. The serum half-life of enterokinase in rats made cirrhotic by inhalation of carbon tetrachloride vapour was extended to 6 min or more. The amount of active enzyme recovered in bile was at least 50% less than in weight-matched normal rats, and excretion was not complete 2h after intravenous administration. The possible significance of these findings in liver and pancreatic disease is discussed.