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H Remmer

Publications and source records attributed to H Remmer.

At least 55 records · Page 3Linked to original sources
PubMed1977

The significance of covalent binding of catechols to proteins in vivo.

When rats were dosed with 14 microgram/kg 3H-isoproterenol, 3H-radioactivity was measurable in the liver until 48 h. This amount was not different in livers of animals which have been pretreated with diethyl maleate. After exhaustive extraction, a significant amount of 3H-radioactivity from isoproterenol could be detected in the proteins of total liver (homogenate), of cytosol and of microsomes. In the cytosol fraction of diethyl maleate pretreated animals twice the amount of isoproterenol-radioactivity was found in the extracted proteins compared to controls. In the microsomal fraction there was no difference between diethyl maleate pretreated and control animals in the amount of radioactivity incorporated into proteins. In all fractions the radioactivity measurable in the extracted proteins declined with a half life time of about 24 h. The in vivo results on covalent binding of isoproterenol are compared to the irreversible protein binding of ethinyloestradiol in vivo. Quantitatively, these in vivo data are compared to the results on irreversible protein binding obtained during incubations of isoproterenol or ethinyloestradiol with rat liver microsomes.

Animals↗
PubMed1976

Implication of rifampicin-quinone in the irreversible binding of rifampicin to macromolecules.

1. When [3H]rifampicin is incubated with rat liver microsomes or rat liver homogenate, minor amounts are bound irreversibly to protein. This effect does not depend on the presence of NAD, NADH, NADP or NADPH. 2. Rifampicin is autoxidized at physiological pH. The product of autoxidation, rifampicin-quinone, if incubated with albumin, shows a much greater irreversible binding to the protein than the parent compound rifampicin. Hence it is concluded that rifampicin may bind irreversibly to proteins in a non-enzymic reaction after autoxidation to rifampicin-quinone. 3. Rifampicin-quinone also binds irreversibly to RNA and poly-L-lysine, if incubated with these compounds. This suggests that free amino groups of protein or RNA are involved in the binding. 4. 48 h after dosage of [3H]rifampicin (33 mg/kg) to rats, 29-2 +/- 4-1 (S.D.) pmol are bound irreversibly to 1 mg liver RNA, 15.8 +/- 8-1 pmol to 1 mg liver protein and 5-0 +/- 0-47 pmol to 1 mg protein in brain tissue. 5. Microsomal NADPH-cytochromcin-quinone to rifampicin. The KM of this reaction is 10(-4) M. Induction of the NADPH-cytochrome c reductase by pre-treatment of rats with 20 mg/kg rifampicin over 5 days results in a corresponding increase of increase of rifampicin-quinone reduction. 6. These results suggest that microsomal NADPH-cytochrome c reductase prevents accumulation of higher amounts of possibly toxic rifampicin-quinone by reduction to rifampicin.

Animals↗
PubMed1976

[Effect of 2-hydroxyestradiol-17beta on NADPH-dependent electron transfer in rat liver microsomes in vitro (author's transl)].

If rat liver microsomes are incubated with NADPH and 2-hydroxyestradiol-17beta in vitro, the following is observed: 1. Inhibition of lipid peroxidation, 2.inhibition of cytochrome P-450 reduction, and 3.inhibition of cytochrome b5 reduction. Beyond this the catechole inhibits lipid peroxidation of liposomes in vitro. These phenomena can be explained by interaction of different states of oxidation of the estrogen with the NADPH-cytochrome reductase and with 0-2 radicals, which leads to terminal "uncoupling" of microsomal electron transport.

Animals↗
PubMed1975

Relationship between microsomal hydroxylase and glucuronyltransferase.

These experiments did not answer the question of whether one or several UDG-glucuronyltransferases are present in endoplasmic membranes of the liver. However, they present results which indicate that the glucuronlytransferase (s) have several properties in common with the hydroxylating cytochrome P-450 dependent enzyme system: the inducibility (which differs considerably after pretreatment with phenobarbital or 3-methylcholanthrene), the sex specificity, and the inhibition by the same compounds. The most obvious difference between the systems is the alteration of the enzyme activities after solubilization of the membranes by sonication or use of detergents.. On solubilization, the activity of the glucuronyltransferase (s) increases, whereas the opposite is true for the hydroxylating system which may lose one or several components essential for its activity (such as the NADPH dependent reductase). Our experiments can best be interpreted by assuming a common micro-environment around the enzymes produced by lipids and proteins which modulate both the rate of hydroxylation and that of glucuronyl-conjugation of drugs.

Aminopyrine↗