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Biomedical subjects

R Teschke

Publications and source records attributed to R Teschke.

At least 73 records · Page 4Linked to original sources
PubMed1980

Alterations of hepatic alcohol metabolizing enzyme activities due to thyroid hormones.

In order to achieve a hyperthyroid state, rats were treated for 7 days with thyroxine (150 microgram/100 g BW) or triiodothyronine (10 microgram/100 g BW). This regimen resulted in an enhanced activity of the microsomal ethanol oxidizing system. In addition, a decrease of hepatic alcohol dehydrogenase activity was observed under these experimental conditions, whereas hepatic catalase activity remained unchanged. These findings suggest that if chronic ethanol consumption simulates a functional "hyperthyroid hepatic state", increased rates of ethanol metabolism observed following prolonged alcohol intake might therefore be attributed at least in part to an induced activity of the microsomal ethanol oxidizing system in the liver.

Aldehyde Oxidoreductases↗
PubMed1980

Decreased hepatotoxicity of dimethylnitrosamine (DMN) following chronic alcohol consumption.

Compared to controls receiving physiological saline, the i.p. administration of dimethylnitrosamine (DMN) on 5 consecutive days to rats fed a nutritionally adequate liquid diet resulted 24 hours after the last injection of significant increases in glutamic dehydrogenase (GDH), glutamic oxylacetate transaminase (GOT), and glutamic pyruvate transaminase (GPT) activities in the serum, indicating a striking hepatotoxic effect of this compound. This was confirmed by the histological demonstration of massive centrolobular necrosis. Conversely, following pretreatment of the rats with an ethanol containing liquid diet for 23 days and subsequent administration of DMN the increases of serum enzyme activities and massive centrolobular necrosis could not be observed. These results therefore suggest that chronic alcohol consumption protects from hepatotoxicity due to DMN, most probably due to an enhancement of detoxifying pathways of the parent component or one of its toxic metabolites.

Alanine Transaminase↗
PubMed1980

Alcoholic liver disease associated with increased gamma-glutamyltransferase activities in serum and liver.

Chronic alcohol consumption leads to increased activities of gamma-glutamyltransferase (GGT) in the serum which are associated with an enhancement of GGT activities in the liver. These findings suggest that increased GGT activities commonly found in alcoholic liver disease can be ascribed primarily to hepatic enzyme induction rather than to liver cell injury, since hepatic GGT activities were increased but not reduced. Moreover, at the fatty liver stage the fetal form of GGT in the serum is much higher in activity that the adult form, whereas the reverse constellation can be found in patients with alcoholic liver cirrhosis. Thus, these preliminary data suggest that the determination of various forms of GGT in the serum of alcoholics may be useful in establishing the particular stage of alcoholic liver disease by a simple enzyme test in the serum.

Alcohol Drinking↗
PubMed1978

[Biochemical and pathophysiological aspects of alcohol metabolism (author's transl)].

The metabolism of ethanol to acetaldehyde proceeds in the liver via alcohol dehydrogenase (ADH) and the microsomal ethanol oxidizing system (MEOS), whereas catalase plays no significant role. ADH is localized in the cytosol, required required NAD+ as cofactor and exhibits a pH optimum in the alkaline range and a Km of less than 2 mM for ethanol. Conversely, the MEOS resides in the endoplasmic reticulum, requires NADPH and O2, is inhibited by CO, and exhibits a Km of about 10 mM for ethanol. The microsomal system also metabolizes higher aliphatic alcohols such as butanol which is not a substrate for catalase. Moreover, it could be separated from ADH and catalase by column chromatography. The MEOS exhibits a variety of properties similar to those of other microsomal drug metabolizing enzymes and is characterized by inducibility of its activity following chronic alcohol consumption, which suggests the involvement of the microsomal system in the adaptive enhancement of ethanol clearance commonly observed in alcoholics.

Acetaldehyde↗
PubMed1978

[Clinical aspects of alcohol induced liver injury (author's transl)].

Chronic alcohol consumption results in early biochemical and ultrastructural alterations of the hepatocyte which in turn may lead to alcoholic fatty liver as well as alcoholic hepatitis and via the central hyaline sclerosis to fibrosis and cirrhosis of the liver. Already at the stage of the alcoholic fatty liver an isolated increase of serum gamma-glutamyltransferase activity can often be observed; it results from hepatic microsomal enzyme induction and may facilitate early recognition of alcoholic liver injury. To establish the diagnosis, however, a histological examination of the liver is necessary. The therapy of alcohol-induced liver injury is based upon an absolute alcohol abstinence since alcohol itself or one of its metabolites are hepatotoxic.

Albumins↗
PubMed1977

Metabolism of alcohol at high concentrations: role and biochemical nature of the hepatic microsomal ethanol oxidizing system.

At intermediate and higher alcohol concentrations, ethanol metabolism proceeds via alcohol dehydrogenase (ADH) and the microsomal ethanol oxidizing system (MEOS), whereas catalase plays no significant role. Following prolonged ethanol consumption, an enhancement of both MEOS activity as well as the rates of ethanol metabolism occurs; the latter persisted despite inhibition of ADH by pyrazole and catalase by sodium axide, suggesting the involvement of MEOS in the adaptive increase. MEOS exhibits characteristics similar to those of other microsomal drug metabolizing enzymes and can be differentiated and isolated from both ADH and catalase activities. Reconstitution of MEOS activity was achieved with partially purified cytochrome P-450 and NADPH-cytochrome c reductase in the presence of synthetic phospholipid.

Alcohol Oxidoreductases↗
PubMed1976

Characteristics of acetaldehyde oxidation in rat liver mitochondria.

Rat liver mitochondria oxidized acetaldehyde (180 muM) at the rate of approximately 12 nmol/min/mg of protein at 37 degrees. This was stimulated by 88% with the addition of ADP. The ADP/O ratio (2.6) was similar to that with glutamate as substrate. 2,4-Dinitrophenol and phenazine methosulfate also stimulated the rate of acetaldehyde oxidation in the mitochondria. By contrast, acetaldehyde metabolism was virtually abolished by rotenone and antimycin A. These results indicate that acetaldehyde oxidation is linked to the mitochondrial respiratory chain and coupled with mitochondrial oxidative phosphorylation. Indeed, little acetaldehyde was metabolized when mitochondrial membranes were disrupted by sodium deoxycholate. In the disrupted mitochondria, however, acetaldehyde oxidation was fully recovered by addition of NAD+, suggesting that the ability of mitochondria to supply NAD+ controls the rate of acetaldehyde oxidation in intact mitochondria. The stimulatory effect of ADP on mitochondrial acetaldehyde oxidation was diminished by increasing the acetaldehyde concentration. Concomitantly, the ADP/O ratio decreased, suggesting an inhibitory effect of high concentrations of acetaldehyde on mitochondrial respiration. Chronic feeding of ethanol significantly reduced the capacity of intact liver mitochondria to oxidize acetaldehyde. This was associated with a significant reduction of the mitochondrial respiration. By contrast, the activity of aldehyde dehydrogenase in disrupted mitochondria remained unchanged.

Acetaldehyde↗