PMID: 4905Jan 1, 1976Paper

Irreversible protein binding of norethisterone (norethindrone) epoxide

Steroids
H Kappus, H M Bolt

Abstract

14,15-3H-Norethisterone-4 beta, 5 beta-epoxide, a metabolite of norethisterone, was incubated with several proteins and nucleic acids. After 30 min incubation 0.19 nmol of the epoxide were irreversibly bound per mg albumin which contains free sulfhydryl groups; proteins without SH-groups, such as concanavalin A, gamma-globulin, DNA and RNA, did not irreversibly bind norethisterone epoxide. A superoxide (O2) generating enzyme system comprised of xanthine oxidase and hypoxanthine was capable of catalyzing the irreversible binding of the parent compound, norethisterone, to albumin, indicating that an oxidation product was formed which reacted with the protein. When norethisterone epoxide was incubated for 60 min with hepatic microsomes of rats in absence of NADPH, about 2.0 nmol of the epoxide were irreversibly incorporated per mg microsomal protein. This binding was increased to 5.2 nmol by addition of a NADPH regenerating system. Addition of glutathione and cytosol decreased only the NADPH-dependent protein binding; phenobarbital pretreatment of rats induced this NADPH-dependent binding of norethisterone epoxide to microsomal protein by a factor of 2. In presence of NADPH, binding of the epoxide to microsomal protein depended on...Continue Reading

References

May 15, 1975·Biochemical Pharmacology·H Kappus, H Remmer
Oct 1, 1974·Clinical Pharmacology and Therapeutics·J R MitchellH Keiser
Jun 1, 1972·Journal of Steroid Biochemistry·W G StillwellR N Stillwell

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Citations

Nov 1, 1980·Archives of Toxicology·H M Bolt, R J Laib
Oct 25, 1985·Pharmaceutisch Weekblad. Scientific Edition·A G SedeeC A Haasnoot
Jan 1, 1980·The Biochemical Journal·P H Jellinck, J H Bowen
Jun 1, 1978·Journal of Steroid Biochemistry·N Bedolla-TovarE Diczfalusy
Feb 1, 1979·Proceedings of the National Academy of Sciences of the United States of America·P R Ortiz de MontellanoB A Mico
Feb 1, 1982·Toxicologic Pathology·J SchupplerP Günzel
Feb 1, 1982·Toxicologic Pathology

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