Activity of human 11-cis-retinol dehydrogenase (Rdh5) with steroids and retinoids and expression of its mRNA in extra-ocular human tissue

This report describes the activity of recombinant human Rdh5 (11-cis-retinol dehydrogenase) with steroids and retinoids and expression of the Rdh5 mRNA in extra-ocular human tissue. The data show that Rdh5 catalyses 9-cis-retinol metabolism equally efficiently as 11-cis-retinol metabolism and recognizes 5 alpha-androstan-3 alpha,17 beta-diol and androsterone as substrates (3 alpha-hydroxysteroid dehydrogenase activity), but not testosterone, dihydrotestosterone, oestradiol and corticosterone (lack of 17 beta-hydroxysteroid and 11 beta-hydroxysteroid dehydrogenase activities). Rdh5 mRNA expression was widespread in extra-ocular tissues with human liver (100 % relative expression in extra-, relative to liver) ocular tissues only) and mammary gland (97 % showing the most intense signals. Other noteworthy relatively intense expression sites included colon (45 %), thymus (43 %), small intestine (39 %), kidney (37 %), bladder (29 %), pancreas and spleen (28 % each), heart (26 %), uterus and ovary (25 % each), testis (22 %) and spinal cord (24 %). Human fetal tissues also expressed Rdh5 with fetal liver showing the most intense expression among the fetal tissues (20 %). Considered along with the identical nucleotide sequences in the untranslated regions of human Rdh5 and human 9-cis-retinol dehydrogenase cDNAs and the nearly identical nucleotide sequences overall (99 % identity), the current results suggest that the two cDNAs represent a single gene product.