Effect of dietary sodium restriction on mrna for aldosterone synthase cytochrome P-450 in rat adrenals

Changes in the level of mRNA for aldosterone synthase cytochrome P-450 (cytochrome P-450_aldo) in rats on dietary sodium restriction were studied by means of Northern and slot blot hybridization using an oligonucleotide probe that allowed differentiation of the message for this enzyme from that for cytochrome P-450_11β. These two enzymes have been shown to be highly homologous with each other, exhibiting 88% homology in their nucleotide sequences in the coding region. Upon sodium restriction for 2 weeks, cytochrome P-450_aldo mRNA in rat adrenals increased 7-fold, whereas the cytochrome P-450_11β mRNA level in the same adrenals did not change significantly. The increase in cytochrome P-450_aldo mRNA paralleled that in cytochrome P-450_aldo protein, as analyzed by immunoblot technique. These results, together with our previous finding that angiotensin II induced cytochrome P-450_aldO in rat adrenocortex [Shibata, H., Ogishima, T., Mitani, F., Suzuki, H., Murakami, M., Saruta, T., &Ishimura, Y. (1991) Endocrinology 128, 2534-2539], suggest that the production of cytochrome P-450_aldo is regulated by angiotensin II at the pretranslational level, most likely at the transcriptional level.