Expression of 11 beta-hydroxylase and aldosterone synthase genes in the rat brain

The terminal stages of cortisol and aldosterone production in the human adr enal gland are catalysed by the enzymes 11 beta-hydroxylase and aldosterone synthase, which are encoded by the CYP11B1 and CYP11B2 genes respectively. Recent studies have suggested that aldosterone and cortisol are also made in other tissues such as the brain, heart and vascular system and may play a role in cardiovascular homeostasis. The aim of this study was to confirm the presence of these enzymes and localise them precisely in the rat brain. Reverse transcription-polymerase chain reaction (RT-PCR)/Southern blotting confirmed transcription of CYP11B1 and CYP11B2 in whole brain and hypothala mus minces from Wistar-Kyoto rats. 11 beta-Hydroxylase and aldosterone synt hase were immunolocalised in paraffin-embedded rat adrenal and brain sectio ns using mouse monoclonal antibodies. Negative controls utilised a mouse mo noclonal antibody raised against a non-mammalian epitope. In the brain, 11 beta-hydroxylase and aldosterone synthase were detected in the cerebellum, especially the Purkinje cells, as well as the hippocampus. The specificitie s of the 11 beta-hydroxylase and aldosterone synthase antibodies were confi rmed by positive immunostaining of the relevant regions of the adrenal cort ex. This is the first direct evidence that steroid hydroxylases involved in the final stages of corticosteroid biosynthesis are present in specific region s of the central nervous system.