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F Ballet

Publications and source records attributed to F Ballet.

At least 19 recordsLinked to original sources
PubMed1995

Cytochrome P4502B follows a vesicular route to the plasma membrane in cultured rat hepatocytes.

BACKGROUND/AIMS: Autoantibodies against cytochrome P450 are found in some forms of autoimmune hepatitis. Cytochrome P450 is synthesized and mainly located in the endoplasmic reticulum but may also be expressed on the plasma membrane of hepatocytes. Vesicles migrate from the endoplasmic reticulum to the Golgi apparatus and then to the plasma membrane along microtubules. We determined the route followed by cytochrome P4502B to reach the plasma membrane. METHODS: Rat hepatocytes were cultured for 2 hours after plating with various inhibitors of cellular trafficking. Detached, uncut, nonpermeabilized hepatocytes were then exposed to a monoclonal antibody specific for cytochrome P4502B and studied by flow cytometry and confocal microscopy. RESULTS: The plasma membrane expression of cytochrome P4502B was markedly decreased after 2 hours of culture with cycloheximide (an inhibitor of protein synthesis), caffeine at 20 degrees C (conditions that decrease vesicular transport from the endoplasmic reticulum to the Golgi apparatus), brefeldin A (which redistributes Golgi components back to the endoplasmic reticulum), monensin (an inhibitor of Golgi functions), and colchicine, vinblastine, or nocodazole (three microtubule inhibitors). CONCLUSIONS: Part of cytochrome P4502B follows a microtubule-dependent vesicular route from the endoplasmic reticulum to the plasma membrane in cultured rat hepatocytes.

Animals↗
PubMed1995

The interleukin-2 receptor down-regulates the expression of cytochrome P450 in cultured rat hepatocytes.

BACKGROUND & AIMS: Interleukin (IL) 2 is used in advanced cancers, but its effects on cytochrome P450 remain unknown. Other cytokines down-regulate hepatic cytochrome P450, but it is not known whether this involves cytokine receptors. The aim of this study was to determine whether the IL-2 receptor is expressed on hepatocytes and whether its activation by IL-2 depresses cytochrome P450 in cultured rat hepatocytes. METHODS: A monoclonal antibody specific for the rat IL-2 receptor alpha chain was used to label the receptor, whereas effects on cytochrome P450 were determined after 24 hours of culture with human recombinant IL-2 (5000 U/mL). RESULTS: The presence of the IL-2 receptor in hepatocytes was shown by immunoblots, flow cytometry, and scanning confocal microscopy. IL-2 caused a 46% decrease in total cytochrome P450; a 35%, 35%, 36%, 26%, and 56% decrease in immunoreactive cytochrome P4501A1, 2B, 2C11, 2D1, and 3A, respectively; and a marked decrease in cytochrome P4503A2 and 2C11 messenger RNAs. Addition to the culture medium of the anti-receptor antibody or the tyrosine kinase inhibitor genistein prevented the IL-2-mediated decrease in cytochrome P450. CONCLUSIONS: IL-2 down-regulates the expression of cytochrome P450 genes in cultured rat hepatocytes by interacting with its receptor expressed on hepatocytes.

Animals↗
PubMed1995

Effects of ursodeoxycholic acid and chenodeoxycholic acid on human hepatocytes in primary culture.

Hepatic bile acid concentrations are elevated in chronic cholestasis because of reduced canalicular excretion and active ileal absorption of the fraction eliminated in the gut. Ursodeoxycholic acid (UDCA) reduces the intestinal absorption of endogenous bile acids, thereby diminishing the concentrations to which liver cells are exposed. In the isolated perfused liver (in which vectorial bile acid transport is maintained), UDCA reduces the cytotoxic and cholestatic effects of endogenous bile acids. As a result, it has been suggested that UDCA or one of its conjugates could have a direct protective effect on hepatocyte structure and function. We therefore studied the effects of chenodeoxycholic acid (CDCA) and tauroursodeoxycholic acid (TUDCA) alone and in combination on the viability and certain functions of human hepatocytes in primary culture. TUDCA did not affect intracellular concentrations of CDCA when added concomitantly. In other experiments, CDCA (100 to 500 mumol/L) induced concentration-dependent increases in lactate dehydrogenase (LDH) leakage and decreases in cellular protein synthesis and albumin secretion. Neither TUDCA nor UDCA had similar effects at the same concentrations, nor did they have a protective effect when added concomitantly with CDCA at equimolar or twice-equimolar concentrations. These results suggest that UDCA has no direct cytoprotective effect when the bile acid concentrations to which human hepatocytes are exposed are unchanged. They also suggest that the hepatoprotective effect of UDCA in cholestatic human liver diseases and in the isolated perfused liver loaded with hydrophobic bile acids occurs through its effect on intestinal and hepatocyte transport systems.

Bile Acids and Salts↗
PubMed1993

Cytochromes P-450 in human hepatocyte plasma membrane: recognition by several autoantibodies.

BACKGROUND: Anti-cytochrome P-450 autoantibodies are present in several forms of autoimmune hepatitis. The possibility that cytochromes P-450 are present in the plasma membrane of human hepatocytes was examined. METHODS: (1) Plasma membranes with microsomal contamination < 1%, as judged from the activities of glucose-6-phosphatase and NADH-cytochrome c reductase, were prepared. (2) After exposure of uncut, fixed hepatocytes to antibodies, immunofluorescence and immunoperoxidase studies were performed. RESULTS: (1) The specific content of cytochrome P-450 in plasma membrane was 9% of that in microsomes. Plasma membranes showed NADPH-cytochrome c reductase and mono-oxygenase activities; immunoblots showed the presence of cytochromes P-450 1A2, 2C, 2D6, 2E1, and 3A4; cytochromes P-450 1A2, 2D6, and 2C were also recognized by anti-liver microsome and anti-liver/kidney microsome type 1 and type 2 autoantibodies, respectively. (2) Immunofluorescence and immunoperoxidase labeling of the plasma membrane was observed with the three auto-antibodies and with anti-cytochrome P-450 1A2, 2C, 2E1, or 3A4. CONCLUSIONS: It is concluded that cytochromes P-450 are present and functional in the plasma membrane of human hepatocytes and that anti-cytochrome P-450 autoantibodies recognize epitopes expressed on the outer surface.

Autoantibodies↗
PubMed1992

Intrasplenic hepatocellular transplantation corrects hepatic encephalopathy in portacaval-shunted rats.

The aim of this work was to evaluate the effect of intrasplenic hepatocellular transplantation on hepatic encephalopathy in an experimental model of chronic liver failure induced by end-to-side portacaval shunt in the rat. Inbred male Wistar Furth rats were divided into three groups: rats subjected to portacaval shunt (n = 10), rats subjected to portacaval shunt and intrasplenic hepatocellular transplantation of 10(7) hepatocytes isolated from livers of syngeneic rats (n = 10) and sham-operated rats (n = 10). Behavior tests were performed in a blind fashion at 3 wk, at 2 mo and at 3 mo after surgery. Spontaneous activity and nose-poke exploration by individual rats were studied in automated open field boxes equipped with infrared cells. Each cell beam interruption was automatically recorded on a microcomputer and transformed into a score index (counts/hour). Plasma levels of amino acids, ammonia and total biliary acids were measured. Portacaval shunt rats showed reduced spontaneous activity and nose-poke exploration scores. Intrasplenic hepatocellular transplantation significantly increased spontaneous activity after 2 mo and improved nose-poke exploration after 3 wk. At 3 mo, spontaneous activity and nose-poke exploration in portacaval shunt/intrasplenic hepatocellular transplantation rats were not significantly different from those of sham rats. Increases in plasma ammonia levels after portacaval shunt were not corrected. Amino acid imbalance and bile acid concentration in plasma were partially corrected by intrasplenic hepatocellular transplantation. These data show that intrasplenic hepatocellular transplantation can correct the neurological symptoms of hepatic encephalopathy in an experimental model of chronic liver failure and suggest that intrasplenic hepatocellular transplantation might be of therapeutic interest in chronic liver failure.

Animals↗
PubMed1992

Actin filament alteration as a potential marker for cholestasis: a study in isolated rat hepatocyte couplets.

It has been suggested that modification of the pericanalicular microfilament network (F-actin) plays a role in cholestasis. The purposes of this study were to assess (i) the process of F-actin network reorganization in isolated rat hepatocyte couplets (IRHC) in order to define the optimal study conditions in this model, (ii) the effect of cholestatic and hepatotoxic but non-cholestatic compounds on F-actin distribution in IRHC. F-actin was stained with fluorescein isothiocyanate phalloidin and fluorimetric measurements were performed in single couplets using a scanning laser cytometer, ACAS 570. F-actin distribution was assessed by the ratio of canalicular area fluorescence/total couplet fluorescence (CF/TF). The organization of the F-actin filaments was restored in IRHC 3-6 h after plating. At non-cytotoxic concentrations, most cholestatic compounds induced a significant accumulation of F-actin around the bile canaliculus as indicated by increased fluorescence in the pericanalicular area and by the increased CF/TF ratio as compared to the controls. This accumulation could be a consequence of an inhibition of F-actin depolymerization or a higher organization of actin (redistribution, bundling or reorientation). Hepatotoxic but non-cholestatic compounds did not induce any change in pericanalicular F-actin. Abnormalities of pericanalicular F-actin therefore appear to be a specific marker of hepatocellular cholestasis.

Actin Cytoskeleton↗
PubMed1992

Branched-chain amino acid metabolism in isolated perfused liver of cirrhotic rats.

We examined the possible contribution of the liver to the alterations in branched-chain amino acid (BCAA) metabolism in cirrhosis. The livers of male Sprague-Dawley rats with CCl4-induced cirrhosis were removed and placed in a recirculating perfusion system. Net amino acid uptake and release were determined over 55 min. Results were compared with those obtained with control animals, which were either pair-fed or fed ad libitum. Intrahepatic amino acid concentrations were determined at the end of the perfusion. The release of isoleucine and leucine was significantly lower in the cirrhotic livers than in the controls fed ad libitum. There was no difference between the cirrhotic and pair-fed groups with regard to the fluxes of the three BCAA. Intrahepatic concentrations of BCAA were reduced only in pair-fed controls. These results suggest that both cirrhosis and a low protein/calorie diet alter hepatic BCAA flux, but via different mechanisms. In cirrhosis, alterations could be due both to low food intake and to BCAA metabolism in non-parenchymal cells.

Amino Acids, Branched-Chain↗
PubMed1991

Experimental model of colon cancer: recurrences after surgery alone or associated with intraperitoneal 5-fluorouracil chemotherapy.

The liver is the most frequent site of metastases in colon cancer. No good animal model has been available to help improve the treatment of liver metastases or their prevention after resection of a primary colon cancer. The aim of this study was to develop a model of colon cancer induced by azoxymethane in the rat and to study the outcome after surgical resection alone or in association with intraperitoneal chemotherapy (5-fluorouracil (5-FU). Three hundred male Wistar rats received subcutaneous azoxymethane (10 mg/kg body weight/week) for 12 weeks. Eighty-three rats with isolated colon cancer underwent total colectomy; 40 of these rats with no metastases were randomized into two groups: surgery alone or surgery plus 5-FU (5 mg/kg body weight/day) for 5 days after surgery. Thirty rats were able to be evaluated. At autopsy, peritoneal carcinomatosis and liver metastases were more frequent in the control group than after adjuvant treatment with 5-FU (27.7 percent vs. 0, P less than 0.05; and 22.2 percent vs. 0, P less than 0.05, respectively). The rates of peritoneal and hepatic recurrence after resection of the primary cancer indicate that the model mimics the natural history of human colon cancer. In this model, 5-FU reduced the rate of peritoneal carcinomatosis and liver metastases but did not influence survival.

Adenocarcinoma↗
PubMed1991

Effect of bile acids on ischemia-reperfusion liver injury.

We investigated whether stimulation of bile flow by taurocholic acid (TCA), ursodeoxycholic acid (UDCA) or its taurine conjugate (TUDCA) could protect the liver from ischemia-reperfusion injury. The isolated perfused rat liver model was used. In livers perfused without bile acids (n = 8), 60 min of ischemia induced a significant reduction in bile flow and in portal flow, together with a marked increase in LDH, AST and uric acid release in the perfusate. These alterations were maximal at the beginning of reperfusion. In livers perfused with TCA (n = 6), UDCA (n = 7) or TUDCA (n = 6), bile flow was significantly increased as compared to controls during the pre-ischemic phase, as well as during the reperfusion phase. However, no significant improvement was observed in any of the biochemical, hemodynamic or histologic parameters studied. The results show that stimulation of bile flow either by TCA, UDCA or TUDCA does not reduce ischemia-reperfusion liver injury. Furthermore, the results do not provide evidence for a cytoprotective effect of UDCA or TUDCA in this model of liver injury.

Animals↗
PubMed1990

Amino acid metabolism in isolated perfused rat liver.

Conflicting evidence concerning hepatic amino acid (AA) metabolism in the isolated perfused rat liver (IPRL) led us to investigate the response of IPRL using perfusates with various AA contents. Perfusion (n = 4) with whole rat blood diluted in Krebs buffer (1:3, v/v) led to acute proteolysis on account of AA deprivation, as shown by the large release of AA (approximately 1400 mumoles in 120 min), especially branched-chain AA (BCAA) (e.g., Leu, 35.4 +/- 10.4 nmole.min-1.g-1 the first hour, 34.3 +/- 5.5 nmole.min-1.g-1 the second hour). In a first attempt to prevent proteolysis, livers (n = 4) were perfused with the previous medium supplemented with AA known for their antiproteolytic activity, at twice their physiological concentrations. Results during the first hour showed uptake of several AA (mainly alanine, glutamine, and proline), reduced release of BCAA (leucine, 12.5 +/- 6.3 nmole.min-1.g-1), and an increase in glucose and urea production. However, during the second hour, because of the use of a recirculating system, progressive AA depletion induced a reappearance of proteolysis. A two-step AA loading technique, i.e., the addition of antiproteolytic AA at the beginning of the perfusion and the addition of a balanced AA mixture at 60 min caused a further decrease in proteolysis during the 2 hr of perfusion (n = 6). Under these conditions, most AA were taken up by the liver with uptake values comparable to those observed in vivo.

Amino Acids↗
PubMed1990

Hepatic circulation: potential for therapeutic intervention.

In recent years, knowledge of the physiology and pharmacology of hepatic circulation has grown rapidly. Liver microcirculation has a unique design that allows very efficient exchange processes between plasma and liver cells, even when severe constraints are imposed upon the system, i.e. in stressful situations. Furthermore, it has been recognized recently that sinusoids and their associated cells can no longer be considered only as passive structures ensuring the dispersion of molecules in the liver, but represent a very sophisticated network that protects and regulates parenchymal cells through a variety of mediators. Finally, vascular abnormalities are a prominent feature of a number of liver pathological processes, including cirrhosis and liver cell necrosis whether induced by alcohol, ischemia, endotoxins, virus or chemicals. Although it is not clear whether vascular lesions can be the primary events that lead to hepatocyte injury, the main interest of these findings is that liver microcirculation could represent a potential target for drug action in these conditions.

Animals↗
PubMed1990

Experimental colorectal liver metastases. Influence of sex, immunological status and liver regeneration.

The liver is the most frequent site of metastases from colon cancer. To improve our knowledge of liver metastases and to develop new adjuvant therapies, a good animal model is necessary. The aims of this study were to obtain a model of liver metastases with intraportal injection of colon adrenocarcinoma cell aggregates (DHDK12 cell line) and to study the effect of various factors, i.e., sex, liver regeneration and immunosuppression, on the development of liver metastasis. Cell aggregates were injected into the portal vein of 59 syngenic male and female BD IX rats following randomization into three groups. Group 1, (control 12 males and 10 females) received only cell aggregates; group 2 (12 males and 10 females) underwent a 70% hepatectomy before cell injection; group 3 (15 males and 10 females) received cyclosporin A injections at a dose of 10 mg/kg per day for 28 days following cell injection. Autopsy was performed at 10 weeks. Liver metastases were more frequent in the male rats in group 3 than in those in group 1 (80% vs. 30%, p less than 0.04). The rate of liver metastases in females was not increased by immunosuppression (22.2% vs. 12.5%, N.S.). Liver resection (group 2) did not significantly modify the incidence of liver metastasis. No female had liver metastases in this group. This relatively simple model rapidly produces liver metastasis with a high yield, but only in male rats. Besides sexual factors, immunosuppression also increased the rate of experimental liver metastasis, while liver regeneration failed to do so.

Adenocarcinoma↗
PubMed1990

[Hepatocyte transplantation. Treatment of hepatic encephalopathy. An experimental study in the rat].

The aim of this work was to assess the effect of intrasplenic liver cell transplantation (ILCT) on hepatic insufficiency induced by a terminolateral portocaval shunt (PCS) in rats. Thirty syngenic Wistar Furth rats were divided up into three groups: (a) rats with PCS (n = 10); (b) rats with PCS then ILCT of 10(7) liver cells isolated from the livers of syngenic rats (n = 10); (c) operated control rats (n = 10). Double-blind behavior tests were carried out two weeks, two months and six months after surgery. The spontaneous motor activity and the exploring activity of each rat were studied in automated cages fitted with infrared diodes. Each interruption of the infrared beam was automatically recorded by a computer and converted into an activity score (number/hour). The spontaneous motor activity and the exploring activity were poor in the rats with PCS. The ILCT significantly increased the spontaneous motor activity and the exploring activity 2 months and 3 weeks after transplantation, respectively. Three months after transplantation, the spontaneous motor activity and the exploring activity in the PCS/ILCT group were not significantly different from those of the control rats. This study shows that ILCT can correct the neurological signs of hepatic encephalopathy in an experimental model of chronic hepatic insufficiency, and suggests that ILCT may produce therapeutic benefits in chronic hepatic insufficiency.

Animals↗
PubMed1990

The isolated perfused rat spleen. An original method for studying the function of hepatocytes transplanted into the spleen.

The aim of this study was to assess directly the function of isolated hepatocytes 1 year after transplantation into the spleen, using an original model of isolated rat-spleen perfusion. Three specific liver functions, albumin synthesis, indocyanine-green clearance, and antipyrine oxidation, were studied. Five x 10(6) isolated hepatocytes were injected into the spleen of syngenic Wistar-Furth rats. One year later, splenectomy was performed, and the splenic pedicle was carefully isolated in order to allow a selective ex vivo perfusion for 3 hr. De novo albumin synthesis was studied by qualitatively using immunoelectrophoresis and autoradiography, and quantitatively using (35S)-methionine incorporation in albumin. De novo albumin synthesis was observed in spleens containing transplanted hepatocytes but not in controls (P less than 0.001); (35S)-methionine incorporation was significantly higher in spleens containing transplanted hepatocytes than in controls (132 +/- 67 cpm/spleen/hr vs. 14 +/- 6 cpm/spleen/hr, P less than 0.001). Antipyrine clearance was significantly higher in spleens with transplanted hepatocytes than in controls (67.4 +/- 4.9 microliters/min/g vs. 0.2 +/- 0.4 microliters/min/g, P less than 0.01). No statistically significant difference was observed with indocyanine-green clearance (4.2 +/- 6.0 microliters/min/g, vs. 5.2 +/- 5.1 microliters/min/g, P greater than 0.05); this was probably due to the absence of compartmentation between the sinusoid and biliary sectors in this model. In conclusion, using this original isolated rat-spleen perfusion model, it was directly observed that 1 year after transplantation, intrasplenic hepatocytes can perform two liver-specific functions, i.e., de novo albumin synthesis and antipyrine clearance.

Albumins↗
PubMed1989

Effect of vasodilators on hepatic microcirculation in cirrhosis: a study in the isolated perfused rat liver.

We studied the effects of a series of vasodilators on intrahepatic vascular resistance of isolated perfused cirrhotic rat livers in basal conditions and during norepinephrine-induced vasoconstriction. Cirrhosis was induced by repeated intraperitoneal injections of carbon tetrachloride. The vasodilators were a nonselective beta-adrenergic antagonist (propranolol), an alpha 1-adrenergic antagonist (prazosin), a nonselective beta-adrenergic agonist (isoproterenol), an alpha 2-agonist (clonidine), nitrovasodilators (nitroglycerin and nitroprusside), calcium channel blockers (verapamil, diltiazem, nifedipine), papaverine, diazoxide and pentoxifylline. In basal conditions, isoproterenol, nitroglycerin, papaverine, pentoxifylline and nitroprusside demonstrated significant vasodilatory activity. However, the response was weak and isoproterenol was the only drug active in the therapeutic range of concentrations. Propranolol, prazosin, verapamil, diltiazem, nifedipine and diazoxide were ineffective. Prazosin, papaverine and pentoxifylline reduced norepinephrine-induced vasoconstriction, whereas isoproterenol, clonidine and propranolol were ineffective. We conclude that several vasodilators can reduce resistance in the cirrhotic rat liver, but their potency is low and few are effective at therapeutic concentrations. Furthermore, their activity may be blunted when resistance is increased by norepinephrine.

Animals↗
PubMed1989

Protective effect of vasodilators on liver function after long hypothermic preservation: a study in the isolated perfused rat liver.

The effects of two vasodilators, papaverine and pentoxifylline (a methylxanthine derivative), on liver function after 19 hr hypothermic preservation were investigated. Hypothermic preservation was performed according to the standard technique, and liver hemodynamics and function were studied during 70 min immediately after reperfusion in an isolated perfused rat liver system. No significant changes occurred after hypothermic storage for 5 hr. However, when the storage was prolonged to 19 hr, bile flow and taurocholate intrinsic clearance were significantly reduced; transaminase release was markedly increased and histological studies demonstrated centrilobular necrosis. Concomitantly, liver blood flow was significantly reduced and intrahepatic vascular resistance was increased. Papaverine and pentoxifylline administered during preservation and at the time of reperfusion significantly improved all parameters. The improvement was more pronounced after pentoxifylline, and this group showed no significant difference in any of the studied parameters from the control livers. The results show that two vasodilators significantly protect the liver during long hypothermic preservation. The data suggest that abnormalities of liver microcirculation are of major importance in the pathogenesis of liver injury after hypothermic storage.

Animals↗
PubMed1989

Effect of D-tryptophan-6-luteinizing hormone-releasing hormone on the tumoral growth and plasma sex steroid levels in cirrhotic patients with hepatocellular carcinoma.

Certain evidence suggests androgen dependence of hepatocellular carcinoma in cirrhotic patients. Consequently, it was postulated that antiandrogen therapy might be effective in the treatment of hepatocellular carcinoma. D-Tryptophan-6-luteinizing hormone-releasing hormone is a potent agonist analog of luteinizing hormone-releasing hormone which, when chronically administered, inhibits the pituitary gonadal axis and testicular androgen secretion in man. We studied the effects of D-tryptophan-6-luteinizing hormone-releasing hormone on tumoral growth in 17 male cirrhotic patients with hepatocellular carcinoma. After 3 to 6 months of therapy, no tumoral response was observed. Furthermore, measurements of plasma levels of testosterone, dihydrotestosterone, androstenedione, estradiol, estrone and sex hormone-binding globulin were performed before and 3 months after initiation of the antiandrogenic treatment. Before treatment, hypoandrogenism and hyperestrogenism were present; D-tryptophan-6-luteinizing hormone-releasing hormone induced a fall in plasma testosterone and dihydrotestosterone levels. Only a moderate decrease in estradiol and no modification of plasma estrone and sex hormone-binding globulin were found, indicating that the hyperestrogenemia of cirrhotic patients could be attributed to an increase in peripheral aromatization of androgens of adrenal origin. The inability of D-tryptophan-6-luteinizing hormone-releasing hormone to reduce the growth of hepatocellular carcinoma is not totally in disagreement with the concept of androgen dependence of hepatocellular carcinoma since D-tryptophan-6-luteinizing hormone-releasing hormone does not inhibit the production of androgens of adrenal origin.

Aged↗