We have developed a highly sensitive quantitative RT-PCR method for the measurement of CYP11B1 (11-hydroxylase) and CYP11B2 (aldosterone synthase) mRNAs to study their expression in the rat brain in response to dietary sodium manipulation and AngII infusion.

Male WKY rats (n = 6) were fed normal, high or low sodium diets for 12 days or were administered AngII or vehicle for 7 days. CYP11B2 and CYP11B1 expression were measured in RNA from adrenal gland and discrete brain regions using real-time quantitative RT-PCR. Sodium restriction increased adrenal CYP11B2 expression 57-fold from 1.0 x 10⁵ ± 0.6 x 10⁵ to 57 x 10⁵ ± 22 x 10⁵ copies/µg RNA (mean±SEM, P < 0.05), in the hippocampus 14-fold from 5.4 x 10² ± 0.8 x 10² to 74 x 10² ± 31 x 10² copies/µg RNA (P < 0.05) and in the cerebellum 5-fold from 1.9 x 10³ ± 0.7 x 10³ to 9.9 x 10³ ± 3.0 x 10³ copies/µg RNA (P < 0.01). CYP11B2 gene expression in the brain stem and hypothalamus was not affected. High sodium diet reduced adrenal CYP11B2 expression to 0.19 x 10⁵ ± 0.1 x 10⁵ copies/µg RNA (P < 0.05) but did not affect CNS expression significantly. AngII significantly increased adrenal CYP11B2 expression but did not affect CNS expression. Brain CYP11B1 mRNA levels were 10-1000-fold higher than CYP11B2 but were unaffected by dietary sodium or AngII.

To summarize, we have identified a local CYP11B2 response to sodium depletion in the hippocampus and cerebellum. This is the first such regulation of CYP11B2 transcription to be identified in the CNS.