Cytochrome P450 and steroid hydroxylase activity in mouse olfactory and vomeronasal mucosa

The aims of this study are to identify the sex steroid-metabolizing cytochr ome P450 enzymes of the vomeronasal organ (VNO) and to determine the activi ties of VNO microsomes to metabolize estradiol, progesterone, and testoster one. Several P450 isoforms, including CYP1A2, CYP2A, CYP2B, CYP2C, CYP2G1, and CYP3A, NADPH P450-reductase, and microsomal epoxide hydrolase were dete cted in mouse VNO, although their expression levels were much lower than th ose in the main olfactory epithelium, VNO microsomes were active toward the three steroid hormones, producing metabolite profiles similar to those see n with olfactory mucosal microsomes, Thus, the mammalian VNO, a steroid hor mone target tissue, contains multiple steroid-metabolizing P450 isoforms an d is capable of metabolic disposition of the three major sex steroid hormon es, These findings support the proposed roles of olfactory mucosal and VNO microsomal P450 enzymes in maintaining cellular hormonal homeostasis and ot her perireceptor processes associated with olfactory chemosensory function. (C) 1999 Academic Press.