title: Different inhibitory effect of etomidate and ketoconazole on the human adrenal steroid biosynthesis.
abstract: The narcotic agent etomidate and the antimycotic drug ketoconazole are known to block steroid biosynthesis in man. To study the different effects of these imidazole derivatives on human adrenal steroid biosynthesis we incubated slices of human adrenal glands with 3H-labeled precursors and increasing concentrations of etomidate or ketoconazole (0-2000 microM). After extraction the labeled metabolites were separated by thin-layer chromatography and quantified by scintillation counting. Etomidate inhibited most potently 11 beta-hydroxylase activity by suppressing the formation of corticosterone from 11-deoxycorticosterone to 1% of control [50% inhibitory concentration (IC50) 0.03 microM] while ketoconazole suppressed 11 beta-hydroxylase to only 39% of control activity (IC50 15 microM). Ketoconazole however, most potently blocked the conversion of 17 alpha-hydroxy-progesterone to androstenedione by C17,20-desmolase to about 15% of control activity (IC50 1 microM) while etomidate showed a much weaker effect on this enzyme with a suppression to 50% of C17,20-desmolase control activity at a concentration of 380 microM. Both imidazole drugs showed a similar strong inhibitory effect on the activity of 17 alpha-hydroxylase (IC50 6-18 microM) and 16 alpha-hydroxylase (IC50 4-8 microM) and did not affect 21-hydroxylase. These in vitro data indicate a predominant inhibitory effect of etomidate on corticosteroid biosynthesis by relative selective inhibition of 11 beta-hydroxylase and of ketoconazole on the adrenal androgen biosynthesis by a predominant inhibition of C17,20-desmolase. This differential inhibitory effect of etomidate and ketoconazole on human steroid biosynthesis may be of clinical importance for a possible therapeutic use of these imidazole derivatives in endocrine disorders.
authors.affiliation: Medizinische Klinik II, Klinikum Grosshadern, Ludwig-Maximilians-Universität München.
authors.forename: M M
authors.initials: MM
authors.lastname: Weber
authors.forename: J
authors.initials: J
authors.lastname: Lang
authors.forename: F
authors.initials: F
authors.lastname: Abedinpour
authors.forename: K
authors.initials: K
authors.lastname: Zeilberger
authors.forename: B
authors.initials: B
authors.lastname: Adelmann
authors.forename: D
authors.initials: D
authors.lastname: Engelhardt
mesh_terms: D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism*; D000446:Aldehyde-Lyases / Q000037:antagonists & inhibitors; D000728:Androgens / Q000096:biosynthesis*; D001189:Aryl Hydrocarbon Hydroxylases; D065607:Cytochrome P-450 Enzyme Inhibitors; D005045:Etomidate / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007654:Ketoconazole / Q000494:pharmacology*; D013252:Steroid 11-beta-Hydroxylase / Q000037:antagonists & inhibitors; D039181:Steroid 16-alpha-Hydroxylase; D013254:Steroid 17-alpha-Hydroxylase / Q000037:antagonists & inhibitors; D013255:Steroid 21-Hydroxylase / Q000037:antagonists & inhibitors; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors
chemical_list: D000728:Androgens; D065607:Cytochrome P-450 Enzyme Inhibitors; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; D039181:Steroid 16-alpha-Hydroxylase; D013255:Steroid 21-Hydroxylase; D013254:Steroid 17-alpha-Hydroxylase; D013252:Steroid 11-beta-Hydroxylase; D000446:Aldehyde-Lyases; D007654:Ketoconazole; D005045:Etomidate