Inhibition of vein graft intimal proliferative lesions in the rat by heparin.

The authors investigated the effect of heparin on the development of myointimal proliferative lesions in a rat vein graft model. Intimal thickening in this model was most pronounced in the anastomotic regions, and was composed principally of vascular smooth muscle cells, as identified by immunocytochemistry with anti-muscle actin antibody, HHF-35. Medial thickening was less cellular, and evenly distributed throughout the grafts. Continuous, intravenous infusion of whole heparin at 0.3 mg/kg/hr effectively inhibited the development of myointimal proliferative lesions, although with no effect on medial thickening. The authors suggest that heparin, through its antiproliferative activity for vascular smooth muscle cells, may have a potentially important pharmacologic role in preventing vein graft failure, which most commonly results from the development of myointimal proliferative lesions.     

Haem and drug-metabolizing enzymes in regenerating rat liver.

Various parameters of haem and drug metabolism were measured during the course of liver regeneration after two-thirds hepatectomy. Partial hepatectomy produced a significant depression in delta-ALA synthetase and delta-ALA dehydratase, and induction in haem oxygenase at an early stage of regeneration. The values returned to normal within 7-14 days. These changes were also accompanied by a marked decline in benzo(a)pyrene hydroxylase and aminopyrene demethylase. The level of glutathione and the activity of glutathione reductase also increased during the early stage of proliferation. The increased level of glutathione with concomitant decrease in drug-metabolizing enzymes and induction in haem oxygenase could be considered as a protective mechanism for the detoxication process, although a contribution from other biotransforming mechanisms cannot be excluded.     

Role of interleukin-1 in the depression of liver drug metabolism by endotoxin.

Endotoxin-resistant C3H/HeJ mice were used to test the hypothesis that a macrophage product, possibly interleukin-1, might mediate the depression of liver cytochrome P-450-dependent drug metabolism in endotoxin-treated mice. Depression of liver drug metabolism by endotoxin was observed in normal mice (C3H/HeN) but not in C3H/HeJ mice. Serum transfer experiments demonstrated that a serum factor was responsible for the depression of liver drug metabolism. Experiments of passive transfer of peritoneal macrophages showed that this endotoxin-induced factor might be a macrophage product. In vitro experiments showed that endotoxin-stimulated monocytes produced a factor that depressed cytochrome P-450-dependent metabolism in cultured hepatocytes. Homogeneous human monocyte and recombinant interleukin-1 also depressed liver drug metabolism both in vivo and in vitro, suggesting that this macrophage product might be involved in the regulation of liver function by the immune system.     

Effects of ischemia on drug-metabolizing microsomal enzymes in rat liver.

The activities of some enzymes and the content of some coenzymes associated with membranes of the endoplasmic reticulum are affected by ischemia in a way which is progressive with the duration of ischemia and selective for the various enzymes. Aminopyrine demethylation and aniline hydroxylation are strongly inhibited; cytochrome P-450 content decreases, though with a different pattern; NADPH- and NADH-cytochrome c reductases and cytochrome b₅ are unchanged; NAD(P)⁺ glycohydrolase is only slightly reduced. In the microsomal enzyme systems which catalyze drug metabolism the step affected by ischemia seems to be at the level of the hydroxylating enzymes proper or at the site of coupling between these enzymes and the rest of the pathway. Phenobarbital pretreatment exerts a marked protective effect on the decay of induced aminopyrine demethylase and aniline hydroxylase and on the content of newly formed cytochrome P-450. Differences in turnover and/or in location and stability within the membranes of these enzymes and coenzymes are discussed as possible causes of the differential damage caused by ischemia. Increased oxidation of NADH and NADPH added to microsomal preparations from ischemic livers is another sign of disturbed function which can be tentatively ascribed to some as yet undefined biophysical change of the microsomal membranes.     

Inhibition of human immunodeficiency virus gene amplification by heparin.

Gene amplification of virus-specific sequences is widely used as a method to detect or confirm human immunodeficiency virus (HIV) infection. In this study we used an enzyme-linked affinity assay to quantify polymerase chain reaction products from whole blood, plasma, and separated mononuclear cells collected in the presence of four common anticoagulants: acid citrate dextrose, sodium EDTA, potassium oxalate, and sodium heparin. Attenuation of the product signal was observed after amplification of nucleic acid extraction from whole blood, washed mononuclear cells, and plasma from specimens collected in sodium heparin. These inhibitory effects on gene amplification could be reversed with heparinase. The addition of as little as 0.05 U of heparin completely inhibited amplification of an HLA-DQa sequence from placental DNA. We conclude that heparin can cause attenuation or inhibition of gene amplification. Acid citrate dextrose and EDTA, which lack inhibitory activity, are the most appropriate anticoagulants for clinical blood samples when polymerase chain reaction amplification is anticipated.     

The effects of iron deficiency on rat liver enzymes.

The effect of iron deficiency on a number or iron containing enzymes in rat liver has been examined. In addition, 6-phosphogluconate dehydrogenase and glucose 6-phosphate dehydrogenase have been assayed. Of the mitochondrial electron transport reactions only succinate-cytochrome C reductase activity was decreased in iron deficient animals. Microsomal reductase enzymes associated with the NADPH-oxidase system were also markedly decreased although cytochrome P450 concentrations were unaffected. Both 6-phosphogluconate dehydrogenase and glucose 6-phosphate dehydrogenase were reduced in young iron deficient rats but the former had returned to control levels at the age of 14 weeks.     

Effects of ethanol on microsomal drug metabolism in aging female rats. II. Inhibition

The effect of aging on the inhibition by ethanol of drug metabolism activity was examined in liver microsomes of female Fischer 344 rats aged 4, 14 and 24 months. Inhibition of aniline hydroxylase activity in microsomes from 4-month-old females occurred at low concentrations of ethanol (0.1 mM) and was predominantly competitive. Aging was associated with a significant increase in apparent Km for aniline in the absence of ethanol (24 +/- 2, 20 +/- 2 and 32 +/- 1 microM in microsomes from 4-, 14- and 24-month-old rats, respectively) and a change from competitive to non-competitive inhibition by ethanol. Inhibition of benzphetamine N-demethylase activity occurred only at high concentrations of ethanol (100 mM) and was non-competitive in nature. There were no significant effects of aging on the kinetics of the reaction or the type of inhibition produced by ethanol. Microsomal ethanol oxidation rates were measured in liver microsomes of 4-, 15- and 25-month-old Fischer 344 rats of both sexes. Ethanol oxidation in males was greater than in females and was decreased significantly in old age. Ethanol oxidation in female rats was unaffected by aging. The results suggest that significant changes in drug/ethanol interactions can occur as a consequence of aging.     

The inhibition of drug metabolism by cimetidine in patients with liver cirrhosis

Summary The effect of cimetidine treatment, 1 g daily over 6 days, on the disposition of theophylline was studied in nine patients with liver cirrhosis and in nine patients without liver disease. Plasma elimination half-life tended to increase from 14.6±8.2 h to 24.3±14.1 h in the cirrhotic patients (P>0.05) and from 8.3±4.2 h to 10.3±4.1 h in the control patients (P<0.05). Total plasma clearance decreased from 0.50±0.23 ml/kg/min to 0.41±0.21 ml/kg/min (P<0.05) in the cirrhotics and from 0.77±0.34 ml/kg/min to 0.58±0.18 ml/kg/min (P<0.05) in the controls. Pretreatment clearance values were also significantly reduced in the cirrhosis group. No change was observed in the volume of distribution of theophylline. The degree of inhibition of theophylline metabolism did not depend on whether the patients were smokers, or whether they had low pretreatment clearance values. In liver cirrhosis, inhibition of drug metabolism by cimetidine varies widely and is unpredictable in the individual patient.Supported by the Deutsche Forschungsgemeinschaft (Gu 86/8-3)     

Changes in cytoplasmic and mitochondrial enzymes in rat liver after ischemia followed by reperfusion

The behavior of cytoplasmic and mitochondrial enzymes has been studied in rat liver at 1, 5, and 24 hr after 60 min of ischemia using histochemical methods. This period of ischemia resulted 24 h after ischemia in liver cell necrosis in about 15% of the volume of the ischemic liver lobes. As early as after 1 hr reperfusion lactate dehydrogenase (LDH, cytoplasm) activity decreased in a certain proportion of the liver parenchymal cells, whereas glutamate dehydrogenase (GDH, mitochondrial matrix) activity started to decrease after 5 hr reperfusion; the activities of mitochondrial membrane enzymes, monoamine oxidase and succinate dehydrogenase, did not decrease before 24 hr of reperfusion. It has been concluded that the early decrease in LDH activity is caused by leakage into the blood and reflects reversible damage; when this decrease is accompanied by a decrease in GDH activity irreversible liver cell damage is assumed. Diminished activity of mitochondrial membrane enzymes, due to leakage and denaturation, is observed when real necrosis can be assessed.     

Alpha-naphthyl-isothiocyanate-induced cholestasis in the rat: studies of liver plasma membrane enzymes.

Oral administration of a single dose of alpha-naphthyl-isothiocyanate (ANIT) to rats produced a conjugated hyperbilirubinaemia, maximal at 2 days and which subsided by 7. The activities of 3 liver plasma membrane enzymes, Mg-2+-ATPase, (Na-+-K-+)-ATPase and 5-nucleotidase, and serum bilirubin levels were studied for up to 7 days after treatment. Activities of the 3 enzymes were significantly decreased at 2 days after treatment and returned to normal by 7, thus varying inversely with the degree of hyperbilirubinaemia. Enzyme histochemistry used to demonstrate canalicular localization of Mg-2+-ATPase in sections of whole liver and of isolated plasma membrane pellets showed that the reduction in activity was not a uniform partial loss, but represented a range of reductions in most canaliculi with a few retaining normal staining intensity. The results suggest that after ANIT intoxication there is a membrane lesion which may be responsible for the observed hyperbilirubinaemia due to the failure of secretion of biliary constituents into the canaliculus. However, more direct studies are necessary to determine whether any one of these enzymes is directly involved in the transport of biliary constituents across the bile canalicular membrane.