GSBS Student Publications

Title

Effects of mifepristone (RU-486) on heme metabolism and cytochromes P-450 in cultured chick embryo liver cells, possible implications for acute porphyria

GSBS Program

Biochemistry & Molecular Pharmacology

UMMS Affiliation

Graduate School of Biomedical Sciences; Department of Medicine, Division of Hematology/Oncology

Date

10-15-1994

Document Type

Article

Medical Subject Headings

5-Aminolevulinate Synthetase; Animals; Cells, Cultured; Chick Embryo; Cytochrome P-450 Enzyme System; Deferoxamine; Heme; Liver; Mifepristone; Porphyrias, Hepatic; Porphyrins; RNA, Messenger

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

Mifepristone (RU-486), a potent progesterone receptor antagonist and inducer of cytochromes P-450, is currently in use in Europe, particularly as a post-coital oral contraceptive. Soon it will be available in the United States, as well. Since progesterone has been implicated in the pathogenesis of acute attacks of porphyria, the use of RU-486 or related compounds might be considered in porphyric patients. However, as with other cytochrome P-450 inducers, RU-486 may have the ability to precipitate or exacerbate attacks of acute porphyria. The acute porphyrias in relapse are associated with an increase in activity of delta-aminolevulinic acid synthase, the first and normally rate-controlling enzyme in heme biosynthesis. We have used primary cultures of chick embryo liver cells to test the ability of RU-486 to induce delta-aminolevulinic acid synthase activity and mRNA, cytochromes P-450, porphyrin accumulation, and heme oxygenase. We found that RU-486, at concentrations observed in human plasma after a single oral dose, induced the mRNA and activity of delta-aminolevulinic acid synthase, both by itself and in the presence of deferoxamine, a potent iron chelator that inhibits ferrochelatase. RU-486 and deferoxamine together also produced significant accumulations of protoporphyrin. These results indicate that RU-486 may pose a risk in patients with known acute porphyria and should be used with caution. RU-486 increased the concentration of total cytochrome P-450, and the activity of erythromycin demethylase, an activity specifically catalyzed by cytochrome P-450 3A. Unlike several other porphyrogens (e.g. hydantoins, barbiturates), RU-486 does not produce accumulation of uroporphyrin or induction of heme oxygenase in chick embryo liver cells.

Rights and Permissions

Citation: Eur J Biochem. 1994 Oct 15;225(2):651-7

Related Resources

Link to article in PubMed

Journal Title

European journal of biochemistry / FEBS

PubMed ID

7957180