Regional and cellular distribution of CYP2D subfamily members in rat brain

1. Human CYP2D6 is present in brain, metabolizes many drugs and has been im plicated in Parkinson's and Alzheimer's diseases and some cancers. It is st ill unclear which of the six known rat CYP2D subfamily members is/are homol ogous to human CYP2D6. 2. In this study, RT-PCR, Southern and Western blotting and immunohistochem ical techniques were used to study the distribution of CYP2D subfamily memb er mRNA and proteins across 10 rat brain regions. CYP2D subfamily mRNA and protein levels were correlated with brain dextromethorphan O-demethylation (DOD), a measure of human CYP2D6 and rat CYP2D1 activities. 3. The data showed a strong relationship between CYP2D1 and CYP2D1-18 with brain DOD activity. In addition, it was shown that CYP2D proteins are prese nt in brain mitochondrial as well as microsomal membranes. CYP2D subfamily member mRNA and proteins varied across brain regions and were highly concen trated in specific cell types. 4. These data strongly suggest that CYP2D1 and not CYP2D5 mediates DOD acti vity in rat brain, and may be the rat homologue of human CYP2D6. The highly localized nature of CYP2D indicates that in specific neurones enzyme level s may approach hepatic levels and, hence, contribute to local alterations i n brain drug metabolism.