Influence of fasting and hemin on microsomal cytochromes and enzymes

Bock, Karl Walter; Fröhling, W; Remmer, H.

doi:10.1016/0006-2952(73)90021-x

Cited by 45 publications

(7 citation statements)

References 31 publications

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“…This suggestion is consistent with the reported inhibition by haematin of the synthesis of other hepatic enzymes, such as 5-aminolaevulinate synthetase and cytochrome P-450 (Marver et al, 1968;Tyrrell & Marks, 1972) and NADPH-cytochrome c reductase and p-nitrophenol-UDP-glucuronyltransferase (Bock et al, 1973). …”

Section: Discussionsupporting

confidence: 81%

Regulation of rat liver tryptophan pyrrolase by its cofactor haem: Experiments with haematin and 5-aminolaevulinate and comparison with the substrate and hormonal mechanisms

Badawy

Evans

1975

Biochemical Journal

156

117

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1. The administration of haematin or 5-aminolaevulinate to rats enhances the activity of liver tryptophan pyrrolase; both endogenous and newly formed apoenzymes become strongly haem-saturated. Haem activation does not stabilize tryptophan pyrrolase. 2. Actinomycin D, puromycin or cycloheximide prevent the activation of the enzyme by 5-aminolaevulinate but not that by haematin. The latter is inhibited by haem-destroying porphyrogens. 3. The combined injection of either haematin or 5-aminolaevulinate with cortisol does not produce an additive effect, whereas potentiation is observed when tryptophan is jointly given with either the cofactor or the haem precursor. 4. Further experiments on the substrate (tryptophan) mechanism of pyrrolase regulation are reported, and a comparison between this and the cofactor and hormonal mechanisms is made., 5. It is suggested that the substrate mechanism may also involve increased haem synthesis. 6. The role of tryptophan pyrrolase in the utilization of liver haem, and as a possible model for the exacerbation by drugs of human hepatic porphyrias, is discussed.

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Section: Discussionsupporting

confidence: 81%

Regulation of rat liver tryptophan pyrrolase by its cofactor haem: Experiments with haematin and 5-aminolaevulinate and comparison with the substrate and hormonal mechanisms

Badawy

Evans

1975

Biochemical Journal

156

117

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“…Our findings are in agreement with those of Bock et al (7), who demonstrated that the content of cytochrome P 450 and of microsomal enzymes decreased (or ex hibited no change at all) if the results were calculated on a whole-liver basis and not as the specific activity per gram of liver.…”

Section: Resultssupporting

confidence: 83%

“…These changes of the metabolic activity are different with various substrates (3,4). Moreover, the conditions of liver perfusion as seen in the preliminary fasting of the organ donor (7), the composition of the perfusion medium (8) and the presence of extrahepatic tumors (2,6,21) may influence the results and alter their significance to a large extent.…”

mentioning

confidence: 99%

Differential Effects of Fasting and Nicotinic Acid on Various Enzymatic Activities of the 9,000 <i>g</i> Fraction of the Perfused Rat Liver

1975

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“…Cytochrome P-450 content was particularly lowered by the low protein diet. The amount of cytochrome P-450 is known to be very sensitive to the quality and quantity of the protein in the diet [18]. Interestingly, epoxide hydrolase activity followed the same pattern.…”

Section: Discussionmentioning

confidence: 49%

Effect of a Dietary Protein Deficiency on the Development of Hepatic Drug-Metabolizing Enzymes in Young Rats

Kiffel¹,

Magdalou²,

Batt³

et al. 1982

Dev Pharmacol Ther

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The effect of protein deprivation on the activities of hepatic drug-metabolizing enzymes was studied in young rats whose mothers had previously been on a proteinrestricted diet during pregnancy. Dietary protein deficiency (5 % lactic casein as the protein source) lowered the amount of cytochrome P-450 and the activities of epoxide hydrolase and UDP-glucuronosyltransferase (UDPGT) (l-borneol as the substrate) by about 45, 63, and 48%, for the first 8 weeks, respectively. Interestingly, UDPGT estimated with p-nitrophenol as the substrate was far less affected than that estimated from l-bomeol glucuronidation. This finding provides further evidence of the heterogeneity of UDPGT. Restoration of a balanced diet for 15 days following protein deprivation quickly restored cytochrome P-450 and enzyme activities to control values. Our experiments showed that the development of drug-metabolizing enzymes was changed more by the diet in young rats than in older rats. This could affect the toxicity of drugs that are normally metabolized by these pathways.

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Influence of fasting and hemin on microsomal cytochromes and enzymes

Cited by 45 publications

References 31 publications

Regulation of rat liver tryptophan pyrrolase by its cofactor haem: Experiments with haematin and 5-aminolaevulinate and comparison with the substrate and hormonal mechanisms

Regulation of rat liver tryptophan pyrrolase by its cofactor haem: Experiments with haematin and 5-aminolaevulinate and comparison with the substrate and hormonal mechanisms

Differential Effects of Fasting and Nicotinic Acid on Various Enzymatic Activities of the 9,000 <i>g</i> Fraction of the Perfused Rat Liver

Effect of a Dietary Protein Deficiency on the Development of Hepatic Drug-Metabolizing Enzymes in Young Rats

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