Neither intestinal sequestration of bile acids nor common bile duct ligation modulate the expression and function of the rat ileal bile acid transporter

The regulatory responses of bile acid (BA) transport in the terminal ileum to perturbations in BA homeostasis are complex, and conflicting results have been reported by different investigators. These studies were designed to examine the response of this system to a reduction in ileal bile salt concentrations at both a functional and molecular level. Common bile duct ligation (BDL) or feeding of a novel bile acid-binding compound, GT31-104HB, for 7 days were used to reduce ileal apical membrane bile salt flux. Apical bile acid transport function was assessed by examining sodium-dependent uptake of [3H]-taurocholate (TC) into brush border membrane vesicles (BBMV). Expression of the apical sodium-dependent bile acid transporter (ASBT) and the ileal lipid-binding protein (ILBP) were assessed by Western blotting with quantitation using [125I]-labeled secondary antibody and a phosphorimager. Neither common BDL nor intestinal sequestration of BA led to a change in ileal bile acid transport function or the expression of the ASBT or the ILBP. These results indicate that a reduction in presentation of bile salts to the apical surface of the terminal ileum does not modulate the expression of the genes involved in their transport.     

Effect of bile duct ligation on bile acid metabolism in rats

The effect of bile duct ligation on the quantitative and qualitative changes of bile acids in serum, liver, urine, and feces, and the concentration of cholesterol and phospholipids in serum and liver were examined in male rats. The concentration of bile acids in serum increased over 100-fold on day 5 but was lower than the 5-day level on days 10 and 15. The concentration in the liver also increased about 10-fold. beta-Muricholic acid predominantly increased but the secondary bile acids, deoxycholic acid and hyodeoxycholic acid, decreased. The urinary excretion of bile acids increased to about 40 mg/day per rat on the first day of bile duct ligation but this increase was reduced on day 2 to about half and remained at that level until day 24. These values exceeded that of fecal bile acids, 12 mg/day per rat, before bile duct ligation. The amount of bile acid sulfates in the urine was as low as 1% of the total. The urinary non-sulfated bile acids consisted mainly of beta-muricholic acid (60%) and cholic acid (20%), while the sulfates contained a considerable amount of unidentified acidic substances (40%) in addition to cholic acid and beta-muricholic acid. The concentration of cholesterol and phospholipids in serum markedly increased on day 5 but declined gradually thereafter. The liver cholesterol concentration did not change but the phospholipid concentration decreased. Fecal sterols did not change in both the total amount and composition. These data indicated that daily synthesis of bile acids, especially beta-muricholic acid, was accelerated in bile duct-ligated rats.     

Stimulation of bile duct epithelial secretion by glybenclamide in normal and cholestatic rat liver

Cholestasis is a cardinal complication of liver disease, but most treatments are merely supportive. Here we report that the sulfonylurea glybenclamide potently stimulates bile flow and bicarbonate excretion in the isolated perfused rat liver. Video-microscopic studies of isolated hepatocyte couplets and isolated bile duct segments show that this stimulatory effect occurs at the level of the bile duct epithelium, rather than through hepatocytes. Measurements of cAMP, cytosolic pH, and Ca2+ in isolated bile duct cells suggest that glybenclamide directly activates Na+-K+-2Cl- cotransport, rather than other transporters or conventional second-messenger systems that link to secretory pathways in these cells. Finally, studies in livers from rats with endotoxin- or estrogen-induced cholestasis show that glybenclamide retains its stimulatory effects on bile flow and bicarbonate excretion even under these conditions. These findings suggest that bile duct epithelia may represent an important new therapeutic target for treatment of cholestatic disorders.     

A simple method for bile duct anastomosis and interval bile collection in the liver-transplanted rat

A mini T-tube is introduced for the bile duct anastomosis of rat liver transplantation as well as interval bile collection. The validity of the T-tube was evaluated in 14 liver-transplanted rats and compared to 14 rats using traditional stent for bile duct anastomosis. Changes of biliary tree after the T-tube anastomosis were examined by T-tube cholangiography on sample rats at 4 days and at 4 months after liver grafting. Additionally, bile volumes and rates of bile salt secretion were compared in the continuously flowing cannula and the chronic T-tube fistula in normal rats. The results show that the mini T-tube facilitates bile duct anastomosis and study of bile secretion after liver transplantation in rats without increase in surgical difficulty or interference of biliary enterohepatic circulation.     

Endocytosis in rat intrahepatic bile duct epithelial cells of horseradish peroxidase injected into the common bile duct or the portal vein

This article reviews the role of the peroxisome in cellular signalling, with particular emphasis on the unique contributions of this organelle to the complex regulatory inter-relationships of cellular processes within the mammalian organism. Among the topics covered are the close alignments between the signalling systems governing peroxisome proliferation and those of the steroid hormone/thyroid hormone/vitamin D nuclear-receptor superfamily; the regulation of the permeability of the peroxisomal membrane; the involvements of lysophosphatidic acid as an intra- and inter-cellular messenger; the special role of the phosphatidylcholine cycle and its derivative messengers in relation to peroxisomal metabolism; peroxisomal contributions to the regulation of oxygen free radical levels in tissues and the significance of these radicals as second messengers; the evidence of peroxisomal influences on inter-cellular signalling from metabolic turnover studies; modifications of the regulatory significance of fatty acids by the peroxisome; the commonalities in metabolic relationships between the peroxisome and other cellular organelles; and regulatory shuttles associated with peroxisomal function. It is concluded that the peroxisome displays several significant interconnections with the cellular-signalling apparatus, that it is capable of imprinting a characteristic influence on the regulatory network in the cell, and that the contributions of this organelle deserve greater consideration in future investigations of cell-signalling phenomena.     

Increased nitric oxide activity in a rat model of acute pancreatitis

BACKGROUND: Overproduction of nitric oxide (NO) via induction of the inducible NO synthase (iNOS) is an important factor in the haemodynamic disturbances of several inflammatory states. AIMS: To identify the role of NO in a caerulein induced model of acute pancreatitis in the rat. METHODS: Arterial blood pressure and plasma NO metabolites were measured at zero and seven hours in adult male Wistar rats administered caerulein (n=10) or saline (n=10). Pancreatic activity of NOS (inducible and constitutive) was assayed biochemically. The pancreatic expression and cellular localisation of NOS and nitrotyrosine (a marker of peroxynitrite induced oxidative tissue damage) were characterised immunohistochemically. RESULTS: Compared with controls at seven hours, the pancreatitis group displayed raised plasma NO metabolites (mean (SEM) 70.2 (5.9) versus 22.7 (2.2) micromol/l, p<0.0001) and reduced mean arterial blood pressure (88.7 (4.6) versus 112.8 (4.1) mm Hg, p=0.008). There was notable iNOS activity in the pancreatitis group (3.1 (0.34) versus 0.1 (0.01) pmol/mg protein/min, p<0.0001) with reduced constitutive NOS activity (0.62 (0.12) versus 0.96 (0.08) pmol/mg protein/min, p=0.031). The increased expression of iNOS was mainly localised within vascular smooth muscle cells (p=0.003 versus controls), with positive perivascular staining for nitrotyrosine (p=0.0012 versus controls). CONCLUSIONS: In this experimental model of acute pancreatitis, iNOS induction and oxidative tissue damage in the pancreas is associated with raised systemic NO and arterial hypotension. Excess production of NO arising from the inducible NO synthase may be an important factor in the systemic and local haemodynamic disturbances associated with acute pancreatitis.     

Postcholestatic alkaline phosphatase activity after relief of bile duct obstruction in the rat

The effects of obstructive cholestasis on the activity of alkaline phosphatase have been extensively studied in serum and liver tissue. However, very little is known about the activity of this enzyme in the postcholestatic condition after relief of the biliary obstruction. The purpose of this study has been to characterize alkaline phosphatase activity in serum, liver and bile in the postcholestatic period and to relate it to changes in bile acid secretory rate. Serum activity and biliary secretory rates of alkaline phosphatase were markedly increased in rats subjected to a reversible obstructive cholestasis for 24 hr or 48 hr and progressively declined along the postcholestatic period to values not significantly different from those of control rats within 48 hr. A significant direct linear relationship between the biliary secretory rates of enzyme activity and bile salts was apparent both in cholestatic groups and in the control groups. The slope of the regression line (units of alkaline phosphatase secreted per micromole of bile salts) was 1.5-fold to 3-fold higher in cholestatic animals. Remarkably, a positive y-intercept of regression lines suggested that a significant fraction of the enzyme was secreted independently of bile salts; this fraction was 18-fold and 34-fold greater in 24-hr and 48 hr cholestatic rats, respectively, compared with that in controls. Sodium taurocholate administered intravenously, either as a bolus or as an infusion at increasing submaximal rates, resulted in parallel increases of bile salt and alkaline phosphatase secretory rates into bile. The enzyme activity secreted per micromole of taurocholate was significantly greater in cholestatic than in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term survival of a patient with bile duct carcinoma by endoscopic biliary drainage

An 80-yr-old female presented with obstructive jaundice. Endoscopic retrograde cholangiopancreatography showed a carcinoma in the middle extrahepatic bile duct, and a biliary endoprosthesis was inserted. Exfoliative cytology of the bile and forceps biopsy of the tumor revealed a papillary adenocarcinoma. Surgical resection could not be done because of her cardiovascular complications, and neither chemotherapy nor radiotherapy was administered. Stents were exchanged and cleaned 21 times because of occlusion and cholangitis. Subsequent serial cholangiogram showed a slow growth of the papillary tumor, but local invasion to the adjacent organs or distant metastasis was not observed. The patient survived for 7 yr and 6 months after insertion of the biliary endoprosthesis.     

Protective effect of melatonin in a non-septic shock model induced by zymosan in the rat

N-acetyl tyrosine (NAT) is hydroxylated by mushroom tyrosinase and the N-acetyl dopa formed is oxidized by the enzyme to N-acetyl dopaquinone (lambda max = 390 +/- 10 nm). H2O2 and NH2OH each shortened the lag period of NAT hydroxylation by the enzyme. H2O2 had an effect on the changes with time in the spectrum of product(s) formed and on the spectrum of the final product(s) obtained when NAT was hydroxylated by mushroom tyrosinase, in a manner suggesting that H2O2 converts N-acetyl dopaquinone to a pink-violet product(s) (lambda max = 490 nm), whereas such a product(s) was not formed in the absence of H2O2. A pink-violet product(s) (lambda max 490 +/- 20 nm) was also formed when NAT was hydroxylated by mushroom tyrosinase in the presence of NH2OH or para amino benzoic acid (PABA), probably as a result of an interaction between N-acetyl dopaquinone and NH2OH or PABA forming mono- or di-oximes. Kojic acid (5-hydroxy-2-hydroxymethyl)-4H-pyran-4-one) inhibited effectively the rate of NAT hydroxylation by mushroom tyrosinase in the absence or presence of H2O2. When NAT was oxidized by the enzyme in the absence of kojic acid, N-acetyl dopaquinone was formed at once and a shoulder at 490-530 nm appeared later. Under identical conditions but in the presence of kojic acid, a yellow product(s), characterized by a peak at 320 +/- 10 nm, was detected, suggesting that N-acetyl dopaquinone oxidizes kojic acid to the yellow product(s). Maltol (3-hydroxy-2-methyl-4H-pyran-4-one), a gamma-pyrone derivative structurally related to kojic acid, also inhibited the rate of NAT hydroxylation by mushroom tyrosinase. The addition of maltol at the plateau phase of the reaction resulted in an immediate decline in absorbance at 400 nm, suggesting that maltol conjugates with N-acetyl dopaquinone, yielding a product(s) characterized by a lower extinction coefficient at 400 nm than that of N-acetyl dopaquinone alone. The final brown-red product(s) formed when NAT was hydroxylated by mushroom tyrosinase was bleached in the presence of ascorbic acid or H2O2.     

Prognostic determinants in extrahepatic bile duct cancer

BACKGROUND/AIMS: The understanding of histopathological prognostic factors is critical to improving surgical outcome. This study investigated the microscopic features of cancer of the extrahepatic bile duct in order to clarify the prognostic determinants affecting surgical outcome. METHODOLOGY: In 90 cancers of the extrahepatic bile duct, the correlation between several microscopic parameters and survival was investigated. Lymphatic, venous, and perineural invasion, and the surgical margin (tumor-free or tumor-positive) were examined with serial step-wise sectioned specimens. RESULTS: Seven pT1-tumors showed no venous or perineural invasion and no lymph node involvement and were associated with prolonged survival (5 year survival, 86%) compared with pT2,3 tumors (23%). In pT2,3 tumors, lymphatic, venous, and perineural invasion was found in 80%, 47%, and 88%, respectively, with no significant differences in occurrence of these parameters according to the origin of the primary tumor. As for survival with pT2,3 tumors, lymph node involvement (58%) and status of the surgical margin were significant parameters (p=.0330 and p=.0309, respectively). In addition, these latter parameters differed significantly according to the origin of the primary tumor. CONCLUSION: In cancer of the extrahepatic bile duct, lymph node involvement and status of the surgical margin were the most important microscopic parameters affecting prognosis.     

Increased intraocular pressure induced by corticosteroids

Twelve patients who were highly responsive to topically administered betamethasone were subjected to various corticosteroid preparations (four times daily for four weeks). Each patient was tested in the same eye with fluorometholone, tetrahydrotriamcinolone, medrysone, and betamethasone and the potential to elvate intraocular pressure was determined. The response of intraocular pressure to all the corticosteroids was dose-related and a highly significant correlation was demonstrated between the concentration of betamethasone and the magnitude of intraocular pressure response. The order of potential of corticosteroids to elevate IOP was betamethasone 0.1%, betamethasone 0.05%, tetrahydrotriamcinolone 1.25%, betamethasone 0.02%, fluorometholone 0.1%, medrysone 1.0%, and betamethasone 0.01%. Tetrahydrotriamcinolone 0.25% and fluorometholone 0.05 and 0.01% failed to elevate intraocular pressure significantly.