Effect of carbon tetrachloride treatment on ethanol metabolism

Toxic effects of combined treatment of 1,2-dichloroethane and ethanol on mouse brain and the related mechanisms

The aim of this study was to explore the mechanisms of brain damage induced by the combined treatment of mice with 1,2-dichloroethane (1,2-DCE) and ethanol. Mice were divided into control group; 1,2-DCE-intoxicated group; ethanol-treated group; and low-, medium-, and high-dose combined treatment groups. Histological observations along with brain organ coefficients and water content were used to measure the brain damage directly and indirectly. The levels of nonprotein sulfhydryls, malondialdehyde (MDA), and superoxide dismutase activity were used as parameters to evaluate oxidative stress in the brain. Protein and messenger RNA (mRNA) levels of cytochrome P450 2E1 (CYP2E1), zonula occludens-1 (occludin and zo-1), aquaporin-4 (AQP4), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase (HO)-1, and the γ-glutamyl cysteine synthetase catalytic and modulatory subunits (γ-GCSc, GR, and γ-GCSm) in the brain were examined by Western blot analysis and quantitative polymerase chain reaction analysis, respectively. Effects of the combined treatment of 1,2-DCE and ethanol were evaluated by analysis of variance with a factorial design. The results suggested that combined exposure to ethanol and 1,2-DCE synergistically increased CYP2E1 protein and mRNA levels, accelerated the metabolism of ethanol and 1,2-DCE in the brain tissue, induced high production of reactive oxygen species (ROS), and increased MDA levels, thereby damaging the blood-brain barrier and causing obvious pathological changes in brain tissue. However, the increased level of ROS activated the Nrf2 signal transduction pathway, promoting the expression of HO-1 and glutathione-related antioxidant enzymes in the brain to protect the cells from oxidative damage.

A new approach to the determination of ethanol elimination rate in vivo: an extension of Widmark's equation

In order to provide more experimental data about a single ethanol elimination sequence, tracer amounts of 14C-labelled ethanol were given intravenously in fed and fasted rats into a preexisting pool of unlabelled ethanol. The profiles of the elimination curves of 14C-labelled ethanol were distinctly different from those of unlabelled ethanol. This necessitated the elaboration of a mathematical model based on a two-compartment system, which by using the early distribution phase of the 14C-labelled ethanol and the linear part of the elimination curve of unlabelled ethanol enables the determination of the time-rate constants for distribution of ethanol, K12 and K21 and ethanol elimination rate Q. It is shown that the ratio K21'/(K21' + K12') is "r", the distribution volume of ethanol in the sense of Widmark, K12' is K12 divided with Va (initial distribution space of ethanol) and K21' is K21 divided with Vb (the peripheral compartment). The mean value +/- S.E.M. is 0.57 +/- 0.05 for fed rats and 0.49 +/- 0.03 for fasted. The slope of the time-concentration curve of ethanol, Widmark's beta, is shown to be K12'/(K12' x K21') x Q where Q is ethanol elimination rate. The mean elimination rate is 0.303 +/- 0.036 mmol x l-1 x min-1 in fed rats and 0.219 +/- 0.015 mmol x l-1 x min.-1 in fasted (P less than 0.05). It is concluded that we are now able to extend Widmark's equation by an independent determination of the distribution factor "r".

Effect of ethanol, carbon tetrachloride, and methyl ethyl ketone on butanol oxidase activity in rat lung and liver

The ability of the rat liver to oxidize 2-butanol via a cytochrome P-450-mediated mixed-function oxidase reaction is well known. The purpose of this study was to examine this microsomal alcohol oxidizing system in rat lung and determine if it could be altered by treatments that inhibit or induce this activity. 2-Butanol was incubated with microsomal preparations from male rats, and methyl ethyl ketone production was measured by gas chromatography. The rate was six to eight times lower in lung than in liver. Administration of low doses of ethanol (0.5 ml/kg and 1.0 ml/kg) ip for 7 d did not alter activity in the liver but was inhibitory in the lung, as was a high dose of 3.0 ml/kg in the liver. Carbon tetrachloride (1.0 ml/kg, ip) decreased activity in both tissues, especially the lung. The effects of the two inhibitors were not additive. Methyl ethyl ketone induced 2-butanol oxidation in both tissues. The lung possesses butanol oxidase activity that is alterable by both inhibitors and inducers.

Time course of the carbon tetrachloride-induced decrease in mitochondrial aldehyde dehydrogenase activity

Hepatic microsomal enzymes like cytochrome P-450 and glucose 6-phosphatase are inhibited after exposure to CCl4 in vivo. Since comparatively less is known about the effects of CCl4 on nonmicrosomal enzymes, we investigated the rapidity by which CCl4 inhibits the low Km mitochondrial aldehyde dehydrogenase (ALDH) isozyme, an enzyme known to be inhibited 24 hr after CCl4 treatment. The activity of this ALDH isozyme was significantly lowered 6 and 12 hr after a single 1 ml/kg intragastric dose of CCl4. The mitochondrial low Km ALDH specific activities exhibited a similar pattern of destruction/inhibition to the documented target enzyme microsomal cytochrome P-450 in that lowest values were observed 6 hr after CCl4. These values were 44 and 37% of control for cytochrome P-450 content and the low Km ALDH activity, respectively. Alcohol dehydrogenase activity, expressed as activity per gram liver, was depressed 12 hr after CCl4 dosing. Finally, the activity of the low Km cytosolic ALDH, the isozyme that metabolizes malondialdehyde at low concentrations, was not affected by CCl4 treatment. The CCl4-induced decline in the activity of the matrix ALDH isozyme occurs earlier than previously reported mitochondrial damage. The study of sensitive enzymes like the low Km ALDH may provide valuable information by which it may be possible to determine the relationship of the truly rapid biochemical effects of CCl4 such as microsomal lipid peroxidation with later effects on nonmicrosomal components.

Studies on carbon tetrachloride-ethanol interactions in mice

Male C57BL/6J (C57) and DBA/2J (DBA) inbred mice were dosed with either corn oil or carbon tetrachloride (CCl4) in corn oil 24 h before a 3.25 g/kg i.p. dose of ethanol. The CCl4 doses were increased in approximate half-log intervals (5, 15, 50, 150 or 500 microliter/kg, intragastrically (i.g.)). Blood acetaldehyde concentrations were significantly increased 1, 2, 3 and 4 h after ethanol administration at CCl4 doses of 15 microliter/kg and higher, with DBA and C57 mice exhibiting similar dose-response effects up to the 150 microliter/kg dose. A CCL4 dose of 500 microliter/kg produced differences in blood acetaldehyde elevation between the two inbred strains (DBA - 5-fold, C57 - 3-fold). Associated with the elevation of blood acetaldehyde content was a decrease in the rat of elimination of ethanol from blood. Using male genetically heterogeneous stock (HS) mice it was shown that phenobarbital pretreatment potentiated the CCl4-induced decrease in in vivo acetaldehyde oxidation. An equimolar dose of CHCl3 (0.5 mmol/kg) was without effect in either control or phenobarbital-pretreated mice. Mice pretreated with 0.5 mmol/kg, i.g., 1,2-dichloroethane, 1, 1,2-trichloroethylene or bromobenzene did not exhibit significant interaction with ethanol. These data show that in vivo acetaldehyde oxidation is inhibited by very low doses of CCl4 (15 microliter/kg, i.g.) and that this inhibition is enhanced by the cytochrome P-450-inducing agent phenobarbital.

The effect of chronic poisoning with carbon tetrachloride on voluntary consumption of ethanol by mice

Mice were chronically poisoned with carbon tetrachloride injected twice weekly, intraperitoneally, in doses of 0.05-0.80 mg/g over 10 to 16 weeks. The poisoned animals, as compared to vehicle-injected controls, showed marginally significant increases in voluntary consumption of ethanol in a three-bottle choice (water, 10% and 20% ethanol continuously available), but not to a degree than could be considered alcoholic. The average daily intakes of ethanol remained within the range of variation for normal animals of this strain; there was no consistent shift in preference from 10% to 20% ethanol, and the distribution of drinking times within the 24-hour cycle remained normal. The relevance of these findings to the clinical problem of alcoholism is that the appetite for alcohol, a potential hepatotoxin, persists despite serious damage to the liver.

Microsomal ethanol oxidation: activity in vitro and in vivo

Studies by several investigators have confirmed that the microsomal fraction of mammalian liver oxidizes ethanol to acetaldehyde in a reaction that requires NADPH and oxygen. Efforts to identify the enzymes involved have produced conflicting opinions of the reaction mechanism, however. Initially, the microsomal mixed function oxidase system was assumed to be capable of oxidizing ethanol in a mechanism that did not involve either alcohol dehydrogenase or catalase. Later evidence suggested that the oxidative enzyme was, in fact, catalase, a contaminant of microsomal preparations and that the mixed function oxidase system merely furnished hydrogen peroxide to the reaction. Much current research supports the latter interpretation. Other workers provide evidence that favors a system in which catalase does not participate. Attempts to define the reaction process have involved studies with catalase inhibitors, kinetic studies of the different reaction systems, and physical separation of catalase from the microsomal components. Questions of the mechanism of microsomal ethanol oxidation may prove to be purely academic, however. Efforts to prove that the system has significant in vivo activity generally have not been successful.