Sex differences in cytochrome P4501B1, an estrogen-metabolizing enzyme, in the rhesus monkey telencephalon

The metabolic enzyme CYPIBI is a recently cloned member of the cytochrorne P450 superfamily, expressed widely throughout primate tissue, including the CNS. Although CYPIBI protein is known to metabolize estradiol to catecholestrogens in the uterus. its localization and function in brain have not yet been described. To better understand CYPIBI distribution, we have combined in situ hybridization (ISH) for its mRNA with immunohistochemistry (IHC) for the CYPIBI protein in selected brain regions of male and female adult rhesus monkey mulatta). Blocks of formalin-fixed tissue obtained from the frontal cortex, hippocampus. thalamus, and amygdala were processed and embedded in paraffin. The), were then sectioned and stained as described for human tissue [Muskhelishvili, L., Thompson. P.A., Kusewitt, D.F., Wang, C., Kadlubar. F.F. 2001. In situ hybridization and immunohistochemical analysis of cytochrome P450 I B I expression in human normal tissues. J. Histochem. Cytochern. 49, 229-236]. Results indicated widespread distribution of CYPIBI mRNA in both male and female monkey frontal cortex, hippocampus. thalamus, and amygdala. In contrast, although CYPIBI protein was co-localized with its mRNA in the female brains, it was primarily restricted to hippocampal pyramidal neurons in the male brains. These results suggest that CYPIBI may subserve widespread metabolic functions in the female primate brain but have more restricted actions within the hippocampal pyramidal neurons of the male. Published by Elsevier B.V.