title: Absence of type 1 11beta-hydroxysteroid dehydrogenase enzyme in koala liver.
abstract: The 11beta-hydroxysteroid dehydrogenases (11beta-HSDs) interconvert 11beta-hydroxysteroids such as cortisol into 11-oxosteroids such as cortisone. In most mammals, 11beta-HSD 1 is expressed predominantly in the liver and is active in both the oxidative (cortisol to cortisone) and dehydrogenase (cortisone to cortisol) directions, whilst 11beta-HSD 2 is expressed predominantly in the kidney and functions as a pure oxidative enzyme. We have investigated 11beta-HSD 1 activity in the Australian koala (Phascolarctos cinereus) and have found no activity (either reductive or oxidative) in hepatic microsomes. Immunoblot analysis of koala hepatic microsomes, using an 11beta-HSD 1 antibody raised against the mouse enzyme, failed to identify immunoreactive protein. Reverse transcriptase-polymerase chain reaction (RT-PCR) of koala liver mRNA and genomic PCR using primers designed against highly conserved regions of 11beta-HSD 1 nucleotide sequences were also negative. Furthermore, Southern and Northern blot analysis of koala genomic DNA and mRNA, respectively, confirmed that the koala lacks the 11beta-HSD 1 gene and gene transcript. These results support the fact that the lack of hepatic 11beta-HSD 1 activity in the koala is due to the absence of the 11beta-HSD 1 gene, and this absence is novel among mammalian species studied to date.
authors.affiliation: Centre for Pharmaceutical Research, School of Pharmaceutical, Molecular and Biomedical Sciences, University of South Australia, North Terrace, SA 5000, Adelaide, Australia.
authors.forename: Sandra
authors.initials: S
authors.lastname: Kong
authors.forename: Ross A
authors.initials: RA
authors.lastname: McKinnon
authors.forename: Behnaz
authors.initials: B
authors.lastname: Mojarrabi
authors.forename: Ieva
authors.initials: I
authors.lastname: Stupans
mesh_terms: D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D000818:Animals; D015152:Blotting, Northern; D015139:Blotting, Southern; D016678:Genome; D006913:Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D008099:Liver / Q000201:enzymology*; D007614:Macropodidae; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar
chemical_list: D012333:RNA, Messenger; D006913:Hydroxysteroid Dehydrogenases; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1