RT Journal Article SR Electronic T1 Identification of 9,13-dicis-retinoic acid as a major plasma metabolite of 9-cis-retinoic acid and limited transfer of 9-cis-retinoic acid and 9,13-dicis-retinoic acid to the mouse and rat embryos. JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 928 OP 936 VO 22 IS 6 A1 G Tzimas A1 J O Sass A1 W Wittfoht A1 M M Elmazar A1 K Ehlers A1 H Nau YR 1994 UL http://dmd.aspetjournals.org/content/22/6/928.abstract AB 9-Cis-retinoic acid (9-cis-RA) has been proposed to be the endogenous ligand of retinoid X receptors. We examined the plasma pharmacokinetics of 9-cis-RA and its metabolites in nonpregnant female NMRI mice after oral dosing with 50 mg 9-cis-RA/kg body weight. Furthermore, we studied the metabolism of 9-cis-RA and its transfer to the embryo following oral administration of the precursor 9-cis-retinaldehyde (9-cis-RAL; 100 mg/kg body weight) to pregnant mice and rats on gestational days 11 and 13, respectively. Following 9-cis-RA administration, plasma levels of 9-cis-RA reached their maximum within 40-60 min and then declined in a monoexponential manner with an apparent half-life of 64 +/- 32 min. A great variety of polar metabolites of 9-cis-RA was found; among them, the beta-glucuronides of 9-cis-RA (9-cis-RAG) and of 9-cis-4-oxo-RA (9-cis-4-oxo-RAG) could be identified. A further prominent polar metabolite of 9-cis-RA in mouse plasma was shown to be an additional RA isomer (distinct from 13-cis-RA and all-trans-RA) whose concentrations weeesimilarly high as those of 9-cis-RA.(ABSTRACT TRUNCATED AT 250 WORDS)