Pharmacologic treatment of cholestasis.
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Cholestasis↗
Biomedical subjects
J Reichen
Publications and source records attributed to J Reichen.
Increased benzodiazepine-like activity is neither necessary nor sufficient to explain acute hepatic encephalopathy in the thioacetamide-treated rat.
Increased levels of natural benzodiazepine receptor agonists, produced in the body (endogenous) or ingested with food (exogenous) have been proposed as one of the factors causing hepatic encephalopathy in both experimental animals and human subjects. However, the divergent response of hepatic encephalopathy to benzodiazepine antagonists sheds doubt on this attractive hypothesis. Acute liver failure was induced in male Sprague-Dawley rats (n = 17) with intraperitoneal thioacetamide (600 mg/kg/day for 3 days) while 14 control rats received vehicle only. Acute liver failure developed in all treated rats (AST: 1,898 +/- 1,359 IU/L vs. controls, 45 +/- 5 IU/L, p < 0.005; bilirubin: 36 +/- 27 mumol/L vs. controls, 1.5 +/- 0.5 mumol/L, p < 0.005; centrizonal necrosis) and grade 3 or 4 hepatic encephalopathy (neurologic assessment and activity monitoring). However, benzodiazepine receptor ligand activity, measured in the supernatant of whole-brain homogenates with a [3H]flumazenil binding competition assay, was clearly increased in only 1 of 17 rats with acute liver failure compared with controls (52.7 +/- 34.1 vs. 44.3 +/- 18.9 ng diazepam equivalents/gm; NS). To evaluate whether the reported increase in benzodiazepine receptor ligand activity could be due to prolonged residence of exogenous benzodiazepine-like substances, additional rats with acute liver failure and controls were treated with diazepam (five doses of 0.5 mg/kg at 12-hr intervals by gavage). Benzodiazepine receptor ligand activity was greater in animals with acute liver failure than in controls (223 +/- 65 vs. 103 +/- 23 ng diazepam equivalents/gm; p < 0.002) 1 to 3 hr after the last diazepam dose.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Abnormal lipid composition of microsomes from cirrhotic rat liver--does it contribute to decreased microsomal function?
We determined to what extent a change in the lipid composition of the smooth endoplasmic reticulum contributes to altered microsomal function in cirrhosis. Rats were rendered cirrhotic either by chronic exposure to phenobarbital/CCl4 (MCIR) or by bile duct ligation (BCIR). Microsomal function was tested in vivo by the aminopyrine breath test (ABT), then microsomes were prepared and their phospholipid and cholesterol composition analysed. ABT was reduced by 35 and 41% in BCIR and MCIR, respectively. Cholesterol in microsomes was increased in both cirrhotic groups. (BCIR + 154%, MCIR + 75%) while total phospholipid content was not affected. As shown in other membrane systems, the phospholipid/cholesterol (PL/XOL) ratio showed an excellent inverse correlation with fluorescence anisotropy determined by diphenylhexatriene fluorescence polarization (r = -0.896). The PL/XOL ratio was significantly correlated with aminopyrine N-demethylation in vivo (r = 0.649). Alterations in the composition of phospholipid groups (an increase in sphingomyelin in both cirrhotic groups, and a decrease in phosphatidylcholine and an increase in phosphatidylethanolamine in BCIR) also contributed to increased membrane rigidity. We conclude that altered membrane fluidity contributes to diminished microsomal function but that other factors must also be involved since the PL/XOL ratio explained only 42% of the variance in aminopyrine N-demethylation.
Animals↗
Effect of food on the bioavailability of low-dose methotrexate in patients with rheumatoid arthritis.
OBJECTIVE: To evaluate the influence of food on the bioavailability of an oral dose of methotrexate in patients with rheumatoid arthritis. METHODS: Methotrexate (15 mg) was given intravenously and orally, with or without a meal, to 10 patients. Blood samples were drawn at specific intervals to evaluate drug levels. RESULTS: Food reduced the peak concentration, from a mean of 0.71 mumoles/liter to 0.49 mumoles/liter (P less than 0.02), and slightly increased the time to peak concentration, from a mean of 1.3 hours to 2.0 hours. Bioavailability was highly variable (range 28-94%) but was not affected by food intake. CONCLUSION: Bioavailability of oral methotrexate shows marked interindividual variation but is not affected by the presence of food.
Absorption↗
Alterations in hepatic fructose metabolism in cirrhotic patients demonstrated by dynamic 31phosphorus spectroscopy.
Quantitative liver function tests are based on the clearance concept and measure the plasma disappearance of a test compound such as galactose. Metabolism is inferred to be predominantly hepatic, and usually no knowledge is obtained of the true time course of metabolite formation. Dynamic 31phosphorus magnetic resonance spectroscopy after intravenous administration of fructose directly measures hepatic sugar metabolism. To determine the feasibility and the utility of 31P magnetic resonance spectroscopy, we studied the responses of six healthy subjects and nine patients with nonalcoholic cirrhosis to a fructose load. Results were related to the impairment of hepatic function assessed by the galactose-elimination capacity test. Liver spectra were acquired in a 1.5 T whole-body nuclear magnetic resonance unit with a surface coil (9-cm diameter) placed ventrally on the liver; the one-dimensional chemical-shift imaging technique was used to obtain spectra from tissue slices parallel to the surface coil. After a basal spectrum had been obtained, fructose (250 mg/kg) was injected intravenously, and further spectra were collected sequentially every 6 min for 1 hr. Formation of monophosphate esters (9% +/- 5% vs. 20% +/- 8% of total area; p less than 0.01) and utilization of inorganic phosphate (5% +/- 4% vs. 11% +/- 3% of total area; p less than 0.005) were markedly decreased in cirrhotic patients. These measures correlated with the severity of the impairment of liver function measured by the galactose-elimination capacity (r = 0.53 to 0.69; p less than 0.05). We conclude that dynamic 31P magnetic resonance spectroscopy is a safe, clinically feasible test that allows detailed insights into biochemical events in liver disease.
Adenosine Triphosphate↗
Reduced activity of the electron transport chain in liver mitochondria isolated from rats with secondary biliary cirrhosis.
Mitochondrial metabolism was studied in liver mitochondria isolated from rats with secondary biliary cirrhosis induced by bile duct ligation for 5 wk. State 3 oxidation rates were decreased in mitochondrial preparations from bile duct-ligated rats as compared with sham-operated control rats by 63% and 42% using beta-hydroxybutyrate and succinate as substrates, respectively. In contrast, when the substrate was ascorbate/N,N,N',N'-tetramethyl-p-phenylenediamine state 3 oxidation rates were not affected by bile duct ligation. Oxidation rates after uncoupling with dinitrophenol were decreased for both beta-hydroxybutyrate and succinate as substrates in mitochondria from bile duct-ligated rats. The phosphate potential was reduced in mitochondria from bile duct-ligated rats (12.5 +/- 0.5 vs. 13.6 +/- 0.2 kcal in control and bile duct-ligated rats, respectively; p less than 0.05). The inner mitochondrial membrane of liver mitochondria from rats with secondary biliary cirrhosis contained three times more cholesterol as compared with control rats, whereas the phospholipid composition was essentially unchanged. Mitochondrial protein content expressed per liver (calculated on the basis of activities of mitochondrial enzymes determined in liver homogenate and in isolated mitochondria) was increased by 50% in bile duct-ligated rats as compared with control rats. In conclusion, the function of the electron transport chain in liver mitochondria isolated from rats with secondary biliary cirrhosis is impaired. This decrease could be related to altered lipid composition of the inner mitochondrial membrane.
Animals↗
Stereological and functional analysis of liver mitochondria from rats with secondary biliary cirrhosis: impaired mitochondrial metabolism and increased mitochondrial content per hepatocyte.
Mitochondrial and cytosolic functions were studied in vivo and in perfused livers from rats with secondary biliary cirrhosis induced by bile duct ligation for 5 wk and in sham-operated controls. The livers were stereologically analyzed, and mitochondrial and cytosolic functions were related to liver structure. Oxygen consumption by perfused livers expressed per stereologically determined mitochondrial volume was decreased by 49% in bile duct-ligated rats compared with control rats. Glucose production (expressed per mitochondrial volume) was reduced by more than 90% in bile duct ligation, whereas urea production was not affected. Lactate production, a cytosolic function, was increased fivefold in bile duct ligation, and both the lactate/pyruvate and the beta-hydroxybutyrate/aceto-acetate ratios were increased in the liver perfusate of bile duct-ligated rats. In comparison with control rats, the stereologically determined mitochondrial volume fraction per hepatocyte was increased by 28% in bile duct-ligated rats. Activities of mitochondrial enzymes expressed per area of mitochondrial membrane or per mitochondrial volume were either unchanged (ATPase, cytochrome c oxidase and glutamate dehydrogenase) or decreased (monoamine oxidase) in bile duct ligation. Thus in comparison with control rats, mitochondrial metabolism is impaired in perfused livers from bile duct-ligated rats; increased mitochondrial volume per hepatocyte may represent a strategy to maintain hepatic energy metabolism in rats with secondary biliary cirrhosis.
Animals↗
Hepatic accumulation of lysosomes and defective transcytotic vesicular pathways in cirrhotic rat liver.
To investigate the potential role of lysosomes in cirrhosis, we analyzed the activity of lysosomal enzymes in rats exposed long-term to phenobarbital and carbon tetrachloride. The activity of lysosomal enzymes was markedly increased in the homogenate of cirrhotic livers (e.g., arylsulfatase 9 +/- S.D.2 vs. 16 +/- 6 nmoles.min-1.mg-1 in control rats and cirrhotic rats, respectively; p less than 0.001). The corresponding plasma levels were also increased (7 +/- 1 vs. 12 +/- 3 nmoles.min-1.mg-1; p less than 0.01), whereas biliary excretion was diminished (16 +/- 7 vs. 7 +/- 2 pmol.min-1.gm liver-1; p less than 0.05) in cirrhotic rats. Stereological quantification of lysosomes visualized cytochemically revealed an increase of pericanalicular lysosomes averaging 1.5 +/- 0.4 around a canaliculus in controls and 3.7 +/- 1.0 in cirrhotic rats (p less than 0.01). Because this suggested a defect in the transcellular vesicular pathway, we investigated the biliary excretion of horseradish peroxidase and epidermal growth factor in perfused livers. Bile flow and total horseradish peroxidase excretion were similar in control rats and cirrhotic rats. However, the early peak of biliary horseradish peroxidase excretion--usually taken as evidence of paracellular transport--was increased in cirrhotic rats (13 +/- 7 vs. 57 +/- 22%; p less than 0.01), whereas the second peak--reflecting the transcellular vesicular pathway(s)--was markedly reduced (87 +/- 7 vs. 43 +/- 22%; p less than 0.001). A similar reduction in the biliary excretion of intact epidermal growth factor and of its degradation products was found. These results demonstrate an increased number of lysosomes in hepatocytes of cirrhotic livers; this appears to be the result of accumulation rather than proliferation, in view of the reduced transcellular vesicular movement of different markers into bile.
Animals↗
Reversibility of secondary biliary fibrosis by biliodigestive anastomosis in the rat.
Biliary cirrhosis with portal hypertension and hepatocellular failure is a well-known complication of extrahepatic obstruction. It is unclear to what extent these changes are reversible by biliodigestive anastomosis. Therefore a rat model of relief of biliary obstruction was developed by performing Roux-en-Y choledochojejunostomy in rats after bile duct obstruction. Patency of the biliodigestive anastomosis was documented by biliary scintigraphy. Microsomal function was assessed in vivo by the aminopyrine breath test and portal hypertension by spleen pulp pressure. Microsomal function was markedly impaired in obstructed animals but recovered after biliodigestive anastomosis. Microsomal cytochrome P450 content paralleled these changes. Similarly, portal hypertension was reversed after successful relief of obstruction. Stereologic analysis showed that biliodigestive anastomosis partially reversed bile ductular proliferation and fibrosis. Studying the time course of recovery showed that restoration of microsomal function was achieved after 2 weeks whereas recovery from portal hypertension required 4 weeks of biliary drainage. Recovery of microsomal function was paralleled by normalization of microsomal lipid composition while resolution of portal hypertension occurred parallel to resolution of the histologic abnormalities.
Anastomosis, Roux-en-Y↗
Ursodeoxycholate has no beneficial effect on liver function or histology in biliary cirrhosis in the rat.
In different cholestatic conditions, the beneficial effects of the tertiary bile acid, ursodeoxycholate, have been described. It is unclear, however, whether ursodeoxycholate also affects the functional and structural alterations induced by chronic biliary obstruction. Therefore, we studied the effect of ursodeoxycholate (100 mg/kg/day) on microsomal function as assessed in vivo by the aminopyrine breath test, on portal hypertension and on the structural composition of the liver in rats with chronic (3-week) biliary obstruction. Hepatic composition was assessed stereologically. Ursodeoxycholate had no effect on any of the parameters measured. We conclude that this form of treatment does not affect advanced liver disease due to common bile duct obstruction. This finding supports one of the proposed mechanisms of action of ursodeoxycholate, namely that it interferes with the ileal absorption of more toxic endogenous bile salts.
Animals↗
Adaptation of mitochondrial metabolism in liver cirrhosis. Different strategies to maintain a vital function.
Mitochondrial function and structure in cirrhotic livers from humans or rats show a variety of changes as compared to control livers. Mitochondrial ATP production is reduced in rats with CCl4- or thioacetamide-induced liver cirrhosis and in rats with secondary biliary cirrhosis. Activity of the electron transport chain is decreased in rats with secondary biliary cirrhosis. In rats with CCl4-induced cirrhosis, the mitochondrial content of certain constituents of the respiratory chain (cytochrome a + a3, cytochrome b and ubiquinone) is increased and activities of cytochrome c oxidase and ATPase are elevated. Similarly, in humans with liver cirrhosis, mitochondrial cytochrome a + a3 content is elevated and has been used to assess the risk for hepatectomy. In rats with secondary biliary cirrhosis, compensatory strategies include increased mitochondrial volume per hepatocyte and possibly increased extramitochondrial ATP production (increased glycolysis). Thus, a variety of adaptive mechanisms are used to maintain mitochondrial function in cirrhotic livers.
Adaptation, Physiological↗
Epidermal growth factor receptor in chronic bile duct obstructed rats: implications for maintenance of hepatocellular mass.
Changes of the number and properties of the epidermal growth factor (EGF) receptor occur during liver regeneration and may be of importance in the maintenance of hepatocellular mass in liver cirrhosis. We therefore studied the changes in the number and distribution of EGF receptor in the development of liver cirrhosis induced by bile duct ligation. Receptor binding assays demonstrated a marked decrease in the binding capacity of crude plasma membrane fractions from 45 +/- SD 16 to 19 +/- 10 fmol/mg protein (p < 0.001) in control and bile duct ligated livers, respectively while the Kd increased after 3 days of bile duct ligation from 0.5 +/- 0.2 to 1.4 +/- 0.6 nmol/l. Total receptor concentration in the same membrane fractions, as assessed by Western blot analysis, was not changed. The expression of EGF receptor mRNA was reduced to about one third of control levels after 28 days of bile obstruction. Immunohistochemistry, performed using monoclonal antibodies against EGF receptor, showed a strong labeling of cytoplasm (87 +/- 3% positive) and plasma membranes (84 +/- 24%) but no labeling of nuclei in control livers. In bile duct ligated rats, in contrast, cytoplasmic staining was decreased (15 +/- 12%) already after 3 days of bile obstruction; labeling of canalicular membranes and nuclei appeared after 14 days. The shift of EGF receptor from plasma membranes to nuclei supports the notion that EGF receptor is involved in the maintenance of hepatocellular mass in this model of liver cirrhosis. This concept is supported by the finding of decreased mRNA for EGF receptor presumably representing down-regulation as seen in regenerating rat liver.
Animals↗
[Drug treatment of cholestatic liver diseases].
After a brief summary of the pathophysiology and natural history of different cholestatic disorders novel forms of treatment are considered. Treatment of different syndromes with ursodeoxycholic acid is considered in some depth. While the substance has clearly proven its efficacy in the symptomatic treatment, its influence on hard parameters such as survival and transplantation requirements remains to be documented. S-adenoylmethionine has shown to be efficaceous in some but not all studies on pruritus of pregnancy. The substance holds promise in other cholestatic disorders as well, but clearly more studies are needed before its therapeutic potential can be appreciated. Finally, nowadays orthotopic liver transplantation should be considered early in patients with progressive cholestatic liver disorders.
Cholestasis, Intrahepatic↗
Regulation of cholesterol and bile acid homoeostasis in bile-obstructed rats.
We examined how total blockage of biliary excretion, the major pathway through which cholesterol and bile acids are removed from the body, affects liver function, cholesterol and bile acid metabolism and homoeostasis. After 4 weeks of bile-duct ligation, rats showed impaired liver function, as documented by elevations in serum bilirubin and alkaline phosphatase activity. Moreover, bile-duct ligation decreased by about 30% both the amount of microsomal cytochrome P-450 in the liver and the elimination of aminopyrine in vivo, a reliable index in vivo of microsomal mixed-function oxidase activity. Cholesterol and bile acid contents in livers of bile-duct-ligated rats were doubled compared with sham-operated controls. Despite the increase in the contents of cholesterol and bile acids in liver, activities of the respective rate-limiting enzymes, 3-hydroxy-3-methylglutaryl-CoA reductase and cholesterol 7 alpha-hydroxylase, were doubled. Serum concentrations of bile acids and free cholesterol increased 25- and 4-fold respectively. The large increase in serum bile acids was associated with a 380-fold increase in the urinary excretion of bile acids. Although there is a general decrease in cytochrome P-450 content and drug metabolism involving cytochrome P-450-containing hydroxylases, the activity of cholesterol 7 alpha-hydroxylase, also a cytochrome P-450-containing enzyme, is actually increased. These data show that complete obstruction of the bile duct results in the selective impairment of microsomal cytochrome P-450. Increased activity of 7 alpha-hydroxylase, bile acid synthesis and urinary excretion provides an alternative excretory pathway that helps to maintain cholesterol homoeostasis when the biliary excretory pathway is eliminated.
Alkaline Phosphatase↗
[The prognostic value of the serial determination of galactose elimination capacity in chronic active hepatitis].
The prognostic value of different conventional liver tests was compared with that of the galactose elimination capacity (GEC) in 37 patients with chronic active hepatitis. During a mean observation period of 4.5 years, 12 patients died of the disease. None of the conventional liver tests (transaminases, prothrombin time, albumin, Child-Pugh classification) discriminated between survivors and nonsurvivors. In contrast, GEC discriminated between survivors and nonsurvivors (p less than 0.04). The best prognostic criterion was a decrease in GEC, since only patients with a decrease died of the disease. The positive and negative predictive values of this criterion were 100 and 60% respectively. This concept could prove useful for stratification purposes in therapeutic trials, as well as in assessment of novel forms of treatment of chronic active hepatitis.
Adult↗
Differential effect of biliary and micronodular cirrhosis on oxidative drug metabolism. In vivo-in vitro correlations of dextromethorphan metabolism in rat models.
Oxidative drug metabolism is impaired in liver cirrhosis; it is unclear, however, whether this depends on the etiology of cirrhosis. Therefore, we studied the metabolism of dextromethorphan in two rat models: biliary cirrhosis induced by bile duct ligation and micronodular cirrhosis induced by chronic exposure to CCl4/phenobarbital. Results were compared with aminopyrine N-demethylation assessed by a breath test in vivo; the latter was reduced to a similar extent in biliary (-41%) and micronodular (-37%) cirrhosis compared to controls. In contrast, clearance of dextromethorphan was significantly (P less than 0.001) reduced in biliary (25.4 +/- 5.3 mL/min/kg) but not in micronodular cirrhosis (48.6 +/- 15.6) as compared to controls (62.2 +/- 16.2). Intrinsic clearance of dextromethorphan in vitro was reduced by 95% and 63% in biliary and micronodular cirrhosis, respectively (P less than 0.001 vs controls). It correlated with dextromethorphan clearance in vivo (r = 0.68, P less than 0.001) whereas correlation with aminopyrine N-demethylation was weak (r = 0.42, P less than 0.05). Our results demonstrate a differential effect of biliary and micronodular cirrhosis on isoenzymes responsible for aminopyrine and dextromethorphan demethylation.
Animals↗
The role of bile salt uptake in canalicular bile formation. Transport systems and acinar heterogeneity.
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Animals↗
Altered density of glomerular binding sites for atrial natriuretic factor in bile duct-ligated rats with ascites.
The renal response to atrial natriuretic factor is blunted in cirrhosis with ascites. This might be due to alterations of renal receptors for atrial natriuretic factor. Therefore density and affinity of glomerular atrial natriuretic factor binding sites of bile duct-ligated rats with ascites (n = 10) and of sham-operated controls (n = 10) were determined. Glomerular atrial natriuretic factor binding sites were identified to be of the B-("biologically active") and C-("clearance") receptor type. Discrimination and quantitative determination of B and C receptors for atrial natriuretic factor were achieved by displacement experiments with atrial natriuretic factor(99-126) or des(18-22)atrial natriuretic factor(4-23), an analogue binding to C receptors only. Density of total glomerular atrial natriuretic factor binding sites was significantly increased in bile duct-ligated rats (3,518 +/- 864 vs. 1,648 +/- 358 fmol/mg protein; p less than 0.05). This was due to a significant increase of C-receptor density (3,460 +/- 866 vs. 1,486 +/- 363 fmol/mg protein; p less than 0.05), whereas density of B receptors was not significantly different in bile duct-ligated rats (58 +/- 11 vs. 162 +/- 63 fmol/mg protein). Affinity of atrial natriuretic factor to its glomerular binding sites did not differ significantly between both groups. These data suggest that an altered glomerular atrial natriuretic factor receptor density could be involved in the renal resistance to atrial natriuretic factor in cirrhosis with ascites.
Animals↗