Expression of cytochrome P45011B1 mRNA in the brain of normal and hypertensive transgenic rats

Cytochrome P45011B1 (11β-hydroxylase) was detected in the brain of male rats by in situ hybridization methods. Normal Sprague-Dawley rats were compared to the transgenic strain TGR(mRen2)27, characterized by the expression of the murine Ren-2(d) renin gene and the development of severe hypertension. Specific riboprobes were generated by in vitro transcription of a 152 base-pair long cDNA template. ³⁵S-labeled riboprobes were hybridized to cryostat sections from adrenal glands and from two different levels of the brain using standard protocols and varying washing conditions. After exposure of the radiolabeled sections to X-ray film, the signals were quantified and compared. Following autoradiography and counterstaining, cytochrome P45011B1 mRNA was clearly localized in the zona fasciculata/reticularis of the adrenal cortex and in distinct layers of the cerebral cortex. High signal densities were obtained in the layers II-IV of the neocortex and in the layer II of the piriform cortex, although the concentrations of cytochrome P45011B1 mRNA were remarkably lower in the central nervous system as compared to adrenal glands. As revealed by the semi-quantitative analysis, there was a slight increase in adrenal 11β-hydroxylase mRNA in the transgenic rats,whereas the brain seems to express nearly the same amount of this enzyme in both strains. The cytochrome P45011B1 mRNA expression in distinct cells, probably nerve cells, and especially in regions with high densities of glucocorticoid receptors points to a possible function of brain derived corticosterone in receptor activation.