Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0023890 (cirrhosis)
 42,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The concentration of cytochrome P-450 and activities of the microsomal enzymes aryl hydrocarbon hydroxylase and ethylmorphine demethylase were measured in hepatic tissue obtained at biopsy from 69 patients. Antipyrine half-life (AP t1/2) was measured simultaneously as an in vivo marker of drug metabolism. Values for each index of the drug-metabolizing system varied greatly, but the mean values in groups of patients with mild hepatitis or inactive cirrhosis did not differ significantly from those of controls. Hepatic cytochrome P-450 content and aryl hydrocarbon hydroxylase activity were lower in patients with severe hepatitis or active cirrhosis than in controls, but ethylmorphine demethylase activity was unchanged in the patients. Drug ingestion was associated with enhancement of drug-metabolizing enzymes in all patients but those with severe liver disease; ethylmorphine demethylase activity was enhanced proportionately more than aryl hydrocarbon hydroxylase activity or cytochrome P-450 concentration. The observation that aryl hydrocarbon hydroxylase and ethylmorphine demethylase activities are influenced to a different extent by liver disease and also by drug ingestion indicates functional heterogeneity of the hepatic microsomal drug-metabolizing system in man. Correlations between t1/2 and hepatic drug oxidases were weak, even when allowance was made for variation in liver size. Thus, the rate of drug metabolism in vivo assessed by measuring AP t1/2 does not appear to be closely related to the activity of some hepatic drug-metabolizing enzymes.
 ...
PMID:Drug metabolism in liver disease: activity of hepatic microsomal metabolizing enzymes. 48 96

The role of liver size in drug metabolism was investigated in 34 chronic alcoholics and 28 controls by comparing antipyrine half-life with biopsy content and total amount of hepatic cytochrome P-450 (P-450) and liver weight. Liver size was significantly greater in alcoholics than in controls. Total P-450 was increased and antipyrine metabolism was enhanced in alcoholics with normal histology of the liver. In subjects with alcoholic hepatitis or cirrhosis, the antipyrine half-life was prolonged and P-450 was decreased. Alcoholics with fatty liver had a reduced P-450 content, but the total amount of P-450 and the antipyrine half-life were normal. The results demonstrate in alcoholics that an enlarged liver of normal histological appearance is associated with enhanced drug metabolism. In subjects with fatty liver the drug metabolizing capacity per unit weight of liver is often impaired, but the increase in liver size leads to undisturbed total oxidizing capacity and normal in vivo metabolism. In alcoholic hepatitis drug metabolism is impaired in spite of hepatomegaly. In cirrhosis the enlargement of the liver appears to compensate for the decreased P-450 content resulting in only slightly decreased total P-450, and the severly impaired in vivo drug metabolism may be due to derangement of blood flow.
 ...
PMID:Liver size and indices of drug metabolism in alcoholics. 63 35

1. Mitochondria and microsomal fractions have been isolated from liver biopsies from patients with alcoholic cirrhosis, cryptogenic cirrhosis or chronic aggressive hepatitis. 2. Cirrhotic livers yieled fewer mitochondria than normal liver. 3. The most significant change was a decrease in mitochondrial respiratory control. Cirrhotic microsomal fractions had a 50% diminution in cytochrome b5 and cytochrome P-450 content. 4. The two patients with chronic aggressive hepatitis showed similar mitochondrial and microsomal changes.
 ...
PMID:Mitochondrial functions and content of microsomal and mitochondrial cytochromes in human cirrhosis. 88 31

Serum zinc and copper levels were studied in relation to in vitro and in vivo drug metabolism in 25 alcoholics, in whom various diseases of the liver had been diagnosed by histology. Serum zinc was elevated in alcoholics with normal or fatty liver and was low in those with alcoholic hepatitis or cirrhosis. There was a significant positive correlation between serum zinc and cytochrome P-450 content of liver biopsies. The relationship between zinc and antipyrine half-life was significant and non-linear. Serum copper level was elevated in all the alcoholics and no significant relationship could be found between copper and drug metabolism in alcoholics. The findings suggest parallelism between changes in serum zinc and indices of drug metabolism in alcoholics.
 ...
PMID:Serum zinc and serum copper and indices of drug metabolism in alcoholics. 92 28

Five unrelated patients with protoporphyria (PP) had diagnostic liver biopsies performed to assess the degree of liver damage. The porphyrin content of the liver was quantitated and characterized and liver damage was assessed. Ultraviolet (UV) microscopy was performed in each case. Liver structure was assessed by light, polarization and electron microscopy. In 3 patients the liver was visualized directly before biopsy through a peritoneoscope. Liver damage ranged from minimal cell necrosis to portal fibrosis; the latter was observed in a 27-year-old sib of a patient (M.I.) who had died, aged 29, 3 years previously in liver failure from PP-related cirrhosis. Liver tissue from the latter patient which was obtained at the time of autopsy was re-examined by light and polarization microscopy. Hepatic pigment deposits, thought to be lipofuscin, showed birefringence on polarization microscopy in two cases, one of them being patient M.I. with PP-cirrhosis. Liver fluorescence on UV microscopy was centrizonal, punctate, faded rapidly and was easily distinguishable from that seen in porphyria cutanea tarda (PCT). The porphyrin content of the liver tissue in biopsied patients was between 5 mug and 80 mug, and in the autopsy case 1600 mug protoporphyrin/g wet weight liver, and on thin layer chromatography only dicarboxylic porphyrins were demonstrable. Hepatic cytochrome P-450 levels in protoporphyria were within normal range. Vmax and Km for aminopyrine-N-demethylation and benzpyrene hydroxylation did not differ significantly from our findings in PCT, variegate porphyria in remission and in non-porphyric controls. However, the activity of hepatic delta-aminolaevulinic acid (ALA) synthetase was significantly enhanced in 2 of the 3 patients in whom this measurement was performed.
 ...
PMID:The hepatic lesion in protoporphyria (PP): preliminary studies of haem metabolism, liver structure and ultrastructure. 100 82

Comparative studies have been conducted of the activity of microsomal mixed-function oxidases from livers of normal, precirrhotic and cirrhotic rats linked with the metabolism of type-I (aminopyrine, hexobarbital), type-II (aniline, metyrapone) and "modified type-II" (corticosterone) substrates. The following factors were investigated: the possible role of cytochrome P-450 content, the state of the "substrate-binding protein" of this enzyme, the degree of affinity of this hemoprotein for both type-I and type-II substrates and finally, the activity of the enzymes of the microsomal electron-transport chain (both in the absence and in the presence of type-I substrate) -- as rate-limiting reactions, "tight spots" in the biotransformation of drugs in experimental microsomes. It was found that the hydroxylation activity for type-II and "modified type-II" substrates during the entire period of liver cirrhosis development is determined by the cytochrome P-450 content and the amplitude of maximal spectral changes observed in the presence of excess substrate. Type-I substrate metabolism, however, is limited in the precirrhotic phase by the state of the "substrate-binding protein" contained in P-450 as well as by the NADPH-cytochrome P-450 reductase activity. On the other hand, the N-demethylating activity in CCl-4-cirrhotic liver microsomes does not depend on either the concentration of P-450, on the amplitude of the maximal spectral changes or on the Ks value. The rate-limiting step in this case is the rate of reduction of the P-450-substrate complex by NADPH.
 ...
PMID:Rate-limiting steps in drug metabolism by microsomes from CCl-4-cirrhotic rat liver. 112 2

Liver microsomes of rats poisoned with thioacetamide show a significant reduction of cytochrome P-450. Consequently, oxidative reactions of drug metabolism and the estrogen 2-hydroxylase are diminished. Enhancement of microsomal transformation of estradiol to estrone and 16alpha-hydroxyestrone is observed after treatment of rats with thioacetamide, due to diminished metabolism of estradiol by the alternative oxidation at C-2. Estriol formation is reduced by thioacetamide pretreatment. These changes in estrogen breakdown closely correlate with those observed in humans suffering from cirrhosis of the liver. It is concluded that the thioacetamide poisoned rat should be an experimental model suitable for studying estrogen metabolism in liver injury.
 ...
PMID:[The thioacetamide-poisoned rat as an animal experimental model for endocrinological studies of estrogen metabolism in chronic liver injury)]. 121 89

In erythropoietic protoporphyria, accumulation of protoporphyrin has been found in various tissues and liver cirrhosis occurs frequently in this disease, probably due to toxic dark effects of protoporphyrin. We have studied the effect of porphyrins on various enzymic functions in rat liver microsomes. Incubation of microsomes with protoporphyrin resulted in a concentration-dependent inhibition of the oxidation of 7-ethoxycoumarin and aminopyrine by the cytochrome P-450 system. Kinetic analysis showed a decrease in Vmax., whereas the Km was not affected (non-competitive inhibition). Furthermore, reduction of cytochrome c by the NADPH-cytochrome P-450 reductase and by the NADH-cytochrome b5 reductase was inhibited. However, the activity of the reductases was only affected when the microsomes were pre-incubated with protoporphyrin, and it was found that the inhibition was dependent on the duration of the pre-incubation. Kinetic analysis again revealed non-competitive inhibition. When these experiments were repeated with uroporphyrin, no inhibition could be observed. With Stern-Volmer plots it was demonstrated that this was most likely caused by the localization of the porphyrins: protoporphyrin is localized in the membrane, whereas uroporphyrin remains in solution. From these results it is concluded that accumulation of protoporphyrin in the liver may markedly affect the cytochrome P-450 system and thus its detoxification function.
 ...
PMID:Toxic dark effects of protoporphyrin on the cytochrome P-450 system in rat liver microsomes. 133 95

Cytochrome P-450 dependent monooxygenases play a dual role for xenobiotic metabolism. On one hand they initiate the primary rate limiting step for the elimination of a bulk of drugs and organic chemicals. On the other hand they catalyze the formation of toxic metabolites from chemical carcinogens and many other toxic chemicals. Numerous studies have shown that their activity in animals is subject to the influence of various modifying factors, such as strain, species, sex, age, diurnal rhythm and the effect of enzyme inducers. Less is known about the influence of these factors on human cytochrome P-450 enzymes. Here we report the results of an extended study on human liver cytochrome P-450 performed with liver biopsies of 178 individuals taken for diagnostic purposes. The enzymatic activity was determined by the aldrin epoxidase assay indicating a variety of enzymes inducible by phenobarbital and by glucocorticoid and androgenic hormones. The frequency histogram of individual aldrin epoxidase activities showed a unimodal distribution and a variation factor of 100 between maximal and minimal activity. Individuals with severe liver diseases, such as cirrhosis and fatty liver, exhibited a 50% loss of enzyme activity. Age and sex did not significantly influence the enzyme activity. No significant correlation was observable between the rate of aldrin epoxidation and debrisoquine 4-hydroxylation, a prototype of a genetically controlled cytochrome P-450 reaction. We assume that the broad interindividual variation of epoxidase activities is more likely due to the influence of exogenous and endogenous inducers rather than to a genetic polymorphism.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Endogenous and exogenous factors modifying the activity of human liver cytochrome P-450 enzymes. 144 64

Despite the epidemiological evidence of a correlation between ethanol abuse and hepatocellular carcinoma, some of the results of experimental and clinical studies remain controversial. Apart from inducing cirrhosis, which may be viewed as a precancerous liver lesion, ethanol may act as a cocarcinogen. Most investigations on this topic have focused on two aspects: ethanol's capacity to induce the cytochrome P-450-dependent microsomal biotransformation system and its interference with at least one DNA repair mechanism. Ethanol exposure enhances the capacity of mixed function oxidases to activate many chemical carcinogens, such as dimethylnitrosamine (DMN). On the other hand, ethanol exposure fails to influence DMN-induced liver carcinogenesis. The capacity of alcohol to inhibit DMN-demethylase activity has not been clearly demonstrated in experiments carried out with human tissue. In conclusion, both the effects of ethanol and their underlying mechanisms as regards liver carcinogenesis are open to debate. The link between ethanol abuse and hepatocellular carcinoma appears to be mediated mainly by its capacity to induce cirrhosis.
 ...
PMID:Hepatocellular carcinoma, alcohol, and cirrhosis: facts and hypotheses. 165 Jun 91


1 2 3 4 5 Next >>