Effect of ethanol on glutathione concentration in isolated hepatocytes.
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ABSTRACT:
SUBMITTER: Vina J
PROVIDER: S-EPMC1161900 | biostudies-other | 1980 May
REPOSITORIES: biostudies-other
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Project description:The effect of extracellular Ca2+ concentration on ethanol oxidation and drug metabolism was studied in isolated rat hepatocytes. Both ethanol oxidation and drug glucuronidation showed similar dependence upon Ca2+, which was a stimulation of activity as Ca2+ was increased to physiological concentration, and inhibition at higher concentration.
| S-EPMC1161859 | biostudies-other
Project description:In hepatocytes isolated from fed rats, acute ethanol pretreatment (at a dose of 5.0 g/kg body wt.) did not change rates of O2 uptake. In cells from starved animals, acute ethanol pretreatment increased O2 uptake by 17-29%. The increased O2 uptake in hepatocytes from starved rats was not accompanied by increased rates of ethanol oxidation, but was accompanied by increased rates of gluconeogenesis under some conditions. The provision of ethanol (10 mM) as a substrate to cells from fed or starved rats decreased O2 uptake in the absence of other substrates or in the presence of lactate, and increased it in the presence of pyruvate or lactate and pyruvate. The results of this study show that the acute effects of ethanol on liver O2 uptake are dependent on the physiological state of the liver. Previously reported large (2-fold) increases in O2 uptake after acute ethanol pretreatment may have been an artefact owing to low control uptake rates (approximately 1.8 micromol/min per g wet wt. of cells) in the liver preparation used. The ATP contents (2.4-2.6 micromol/g wet wt. of cells) and rates of O2 uptake (2.5-5.0 micromol/min per g wet wt. of cells) of cells used in the present study were the same as values reported under conditions close to those in vivo. Therefore the increase in O2 uptake in cells from starved rats after acute ethanol pretreatment is likely to be of physiological significance.
| S-EPMC1152660 | biostudies-other
Project description:1. Hepatocytes isolated from starved rats and incubated without other substrates oxidized ethanol at a rate of 0.8-0.9mumol/min per g wet wt. of cells. Addition of 10mm-lactate increased this rate 2-fold. 2. Quinolinate (5mm) or tryptophan (1mm) decreased the rate of gluconeogenesis with 10mm-lactate and 8mm-ethanol from 0.39 to 0.04-0.08mumol/min per g wet wt. of cells, but rates of ethanol oxidation were not decreased. From these results it appears that acceleration of ethanol oxidation by lactate is not dependent upon the stimulation of gluconeogenesis and the consequent increased demand for ATP. 3. As another test of the relationship between ethanol oxidation and gluconeogenesis, the initial lactate concentration was varied from 0.5mm to 10mm and pyruvate was added to give an initial [lactate]/[pyruvate] ratio of 10. This substrate combination gave a large stimulation of ethanol oxidation (from 0.8 to 2.6mumol/min per g wet wt. of cells) at low lactate concentrations (0.5-2.0mm), but rates remained nearly constant (2.6-3.0mumol/min per g wet wt. of cells) at higher lactate concentrations (2.0-10mm). 4. In contrast, owing to the presence of ethanol, the rate of glucose synthesis was only slightly increased (from 0.08 to 0.12mumol/min per g wet wt. of cells) between 0.5mm- and 2.0mm-lactate and continued to increase (from 0.12 to 0.65mumol/min per g wet wt. of cells) with lactate concentrations between 2 and 10mm. 5. In the presence of ethanol, O(2) uptake increased with increasing substrate concentration over the entire range. 6. Changes in concentrations of glutamate and 2-oxoglutarate closely paralleled changes in the rate of ethanol oxidation. 7. In isolated hepatocytes, rates of ethanol oxidation are lower than those in vivo apparently because of depletion of malate-aspartate shuttle intermediates during cell preparation. Rates are returned to those observed in vivo by substrates that increase the intracellular concentration of shuttle metabolites.
| S-EPMC1185658 | biostudies-other
Project description:Hepatocytes were isolated from fed female rats and incubated with a redox indicator system consisting of cyclohexanone and unlabelled or perdeuterated cyclohexanol. The concentrations and deuterium contents of these were measured by g.l.c. and g.l.c.-m.s. of oxime t-butyldimethylsilyl derivatives. The equilibrium composition represented the redox state of the coenzyme bound to alcohol dehydrogenase, since 4-methylpyrazole inhibited the interconversion. Reduction appeared to be catalysed to a small extent also by an NADPH-dependent aldehyde reductase. The NADH/NAD+ ratio on alcohol dehydrogenase was 3 orders of magnitude higher in the presence of ethanol than in its absence. This redox shift has the degree expected from reported kinetic constants. The shift was due both to a decreased rate of oxidation and to an increased rate of reduction in the indicator system. The results indicate that the redox effect of ethanol on the free NAD system is due to efficient removal of acetaldehyde from a near-equilibrium system consisting of ethanol, acetaldehyde and bound coenzymes, together with dissociation of NADH from the enzyme. The effect on the redox state of the bound coenzyme was less marked when the ethanol was deuterated at C-1, indicating an isotope effect. The 2H excess in the cyclohexanol formed was about 70% of that in the [1,1-2H2]ethanol. This dilution, which is caused by binding of free NADH to the enzyme, indicates that reoxidation of cytosolic NADH partly limits the rate of ethanol oxidation.
| S-EPMC1148579 | biostudies-other
Project description:Isolated rat hepatocytes were cultured in a modified HI-WO/BA medium for 16 h. In the following 24 h oleate or oleate plus ethanol was added to the medium. After this period the medium was changed again and the cultures were further incubated with [1-14C]oleate alone or with [1-14C]oleate plus ethanol for 6 h. This allowed a comparison of effects of short-term (6 h) and long-term (24 + 6 h) exposure to ethanol on fatty acid metabolism. The increased intracellular accumulation of triacylglycerol in the presence of ethanol was quantitatively accounted for by increased fatty acid uptake, by decreased fatty acid oxidation in the tricarboxylic acid cycle and by decreased VLDL (very-low-density lipoprotein)-triacylglycerol secretion. Ketone-body production was not affected. After short-term exposure the rate of accumulation of triacylglycerol was increased by 50%. This increase was accounted for by increased fatty acid uptake (44%), decreased tricarboxylic acid-cycle activity (49%) and decreased VLDL-triacylglycerol secretion (7%). After long-term exposure, the rate of accumulation of triacylglycerol was increased by 74%. This increase was accounted for by increased fatty acid uptake (34%), decreased tricarboxylic acid-cycle activity (34%) and decreased VLDL-triacylglycerol secretion (32%). The larger increase in accumulation of triacylglycerol after long-term exposure to ethanol was entirely accounted for by increased inhibition of secretion of VLDL-triacylglycerol. The biochemical mechanisms underlying the observations are discussed.
| S-EPMC1145037 | biostudies-other
Project description:The ability of glucagon and of adrenaline to affect the concentration of fructose 2,6-bisphosphate in isolated hepatocytes was re-investigated because of important discrepancies existing in the literature. We were unable to detect a significant difference in the sensitivity of the hepatocytes with regard to the effect of glucagon to initiate the interconversion of phosphorylase, pyruvate kinase, 6-phosphofructo-2-kinase and fructose 2,6-bisphosphatase, and also to cause the disappearance of fructose 2,6-bisphosphate. In contrast, we have observed differences in the time-course of these various changes, since the interconversions of phosphorylase and of pyruvate kinase were at least twice as fast as those of 6-phosphofructo-2-kinase and of fructose 2,6-bisphosphatase. When measured in a cell-free system in the presence of MgATP, the cyclic AMP-dependent interconversion of pyruvate kinase was 5-10-fold more rapid than those of 6-phosphofructo-2-kinase and of fructose 2,6-bisphosphatase. These data indicate that 6-phosphofructo-2-kinase and fructose 2,6-bisphosphatase are relatively poor substrates for cyclic AMP-dependent protein kinase; they also support the hypothesis that the two catalytic activities belong to a single protein. Adrenaline had only a slight effect on the several parameters under investigation, except for the activation of phosphorylase. In the absence of Ca2+ ions from the incubation medium, however, adrenaline had an effect similar to that of glucagon.
| S-EPMC1152320 | biostudies-other
Project description:ObjectiveEthanol is a common excipient used in liquid medications to enhance solubility and inhibit -bacterial growth. While the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) have released guidance for how much ethanol is acceptable in medicines, many medications contain more than the recommended amount. The objective of this study was to determine what effect these medications would have on blood alcohol concentration (BAC) for pediatric patients, defined as those medications that would increase the BAC by ≥2.5 mg/dL.MethodsA list of medications dispensed to pediatric patients from a single hospital over a period of 4 months was obtained. The package inserts of these medications were reviewed to determine ethanol content. Typical doses were used to determine the amount of ethanol pediatric patients weighing 10, 20, and 40 kg would receive. The theoretical BAC was then calculated for each medication containing ethanol.ResultsSeven hundred ninety-six medications were dispensed for pediatric patients during the study period, of which 33 contained ethanol. Seven medications would be projected to increase the BAC above 2.5 mg/dL with a normal pediatric dose.ConclusionWhile most medications do not contain ethanol, we found 7 that contained enough ethanol to potentially raise the BAC above 2.5 mg/dL. Health care practitioners should consider the ethanol content of medications prior to recommending them in children and when assessing overdoses.
| S-EPMC11001219 | biostudies-literature
Project description:Alcohol abuse is a global health problem causing a substantial fraction of chronic liver diseases. Abundant TGF-β-a potent pro-fibrogenic cytokine-leads to disease progression. Our aim was to elucidate the crosstalk of TGF-β and alcohol on hepatocytes. Primary murine hepatocytes were challenged with ethanol and TGF-β and cell fate was determined. Fluidigm RNA analyses revealed transcriptional effects that regulate survival and apoptosis. Mechanistic insights were derived from enzyme/pathway inhibition experiments and modulation of oxidative stress levels. To substantiate findings, animal model specimens and human liver tissue cultures were investigated. RESULTS:On its own, ethanol had no effect on hepatocyte apoptosis, whereas TGF-β increased cell death. Combined treatment led to massive hepatocyte apoptosis, which could also be recapitulated in human HCC liver tissue treated ex vivo. Alcohol boosted the TGF-β pro-apoptotic gene signature. The underlying mechanism of pathway crosstalk involves SMAD and non-SMAD/AKT signaling. Blunting CYP2E1 and ADH activities did not prevent this effect, implying that it was not a consequence of alcohol metabolism. In line with this, the ethanol metabolite acetaldehyde did not mimic the effect and glutathione supplementation did not prevent the super-induction of cell death. In contrast, blocking GSK-3β activity, a downstream mediator of AKT signaling, rescued the strong apoptotic response triggered by ethanol and TGF-β. This study provides novel information on the crosstalk between ethanol and TGF-β. We give evidence that ethanol directly leads to a boost of TGF-β's pro-apoptotic function in hepatocytes, which may have implications for patients with chronic alcoholic liver disease.
| S-EPMC5833779 | biostudies-literature
Project description:Ethanol causes a transient activation of the phosphoinositide-specific phospholipase C in intact hepatocytes and mimics the action of receptor-mediated agonists [Hoek, Thomas, Rubin & Rubin (1987) J. Biol. Chem. 262, 682-691]. Preincubation of the hepatocytes with phorbol esters which activate protein kinase C prevented this effect of ethanol: phorbol ester treatment inhibited the ethanol-induced phosphorylase activation, the increase in intracellular free Ca2+ concentrations measured in quin 2-loaded hepatocytes, and the changes in concentrations of inositol phosphates, phosphoinositides and phosphatidic acid. Several lines of evidence indicate that these effects were mediated by protein kinase C. Phorbol esters acted in a concentration range where they activate protein kinase C; phorbol esters that do not activate protein kinase C were not effective in inhibiting the effects of ethanol. The permeant diacylglycerol oleoyl-acetylglycerol also inhibited the effects of ethanol, but other diacylglycerols were not effective in the intact cells. The inhibition of ethanol-induced Ca2+ mobilization by phorbol esters was prevented by preincubating the cells with the protein kinase C inhibitors 1-(5-isoquinolinesulphonyl)-2-methylpiperazine (H7) and sphingosine. H7 also enhanced the Ca2+ mobilization induced by ethanol in cells that were not pretreated with phorbol esters, indicating that the transient nature of the ethanol-induced Ca2+ mobilization may be due to an activation of protein kinase C caused by the accumulation of diacylglycerol. These data support a model whereby ethanol activates the phosphoinositide-specific phospholipase C, possibly by affecting receptor-G-protein-phospholipase C interactions in the membrane.
| S-EPMC1149082 | biostudies-other
Project description:The presence of adenosine (25-250 microM) or of 2-chloroadenosine (2.5-100 microM) in the incubation medium caused a marked decrease in the concentration of fructose 2,6-bisphosphate in isolated hepatocytes. This effect was accompanied by an increase in the concentration of cyclic AMP, an activation of phosphorylase and of fructose 2,6-bisphosphatase, and an inactivation of pyruvate kinase and of 6-phosphofructo-2-kinase. As a rule, the changes in the fructose 2,6-bisphosphate-modifying system were slower but more persistent than those in the activities of phosphorylase and pyruvate kinase. The effect of the nucleoside to decrease the concentration of fructose 2,6-bisphosphate was not affected by an inhibitor of adenosine transport and could not be obtained in a liver high-speed supernatant. These data indicate that the effect of adenosine to decrease the concentration of fructose 2,6-bisphosphate is mediated by the stimulation of adenylate cyclase, secondary to the binding of adenosine to membranous receptors. Like glucagon, 2-chloroadenosine stimulated gluconeogenesis in isolated hepatocytes, whereas adenosine had an opposite effect.
| S-EPMC1153319 | biostudies-other