Regulation of expression of cytochrome P-450 2D mRNA in rat brain with steroid hormones.

Cytochrome P-450 2D is a subfamily of the cytochrome P-450-dependent mixed function oxidase system which is widely distributed in the various tissues of mammals. Sex steroid hormones have been shown to affect the expression of CYP2D in rat brain. Testosterone treatment of ovariectomized female rats elicits a dramatic increase in CYP2D expression, estrogen treatment brings about a modest increase in brain CYP2D expression and reduces the increase in CYP2D expression elicited with testosterone when the two hormones are coadministered. Polymerase chain reaction (PCR) has been used in our laboratory, as well as other laboratories, to measure the low levels of message for various P-450s in brain [Hodgson, A.V., White, T.B., White, J.W., Strobel, H.W., 1993. Expression analysis of the mixed function oxidase system in rat brain by the polymerase chain reaction. Mol. Cell. Biochem. 120, 171-179; Omiecinski, C.J., Redlich, C.A., Costa, P., 1990. Induction and developmental expression of cytochrome P450IA1 messenger RNA in rat and human tissues: detection by the polymerase chain reaction. Cancer Res. 50, 4315-4321]. In this study, competitive PCR (cPCR) approaches have been used to determine effects of progesterone and testosterone on CYP2D expression levels in brains of intact and ovariectomized female rats. When administered for seven treatments, testosterone significantly increases the expression of CYP2D in brain from intact female rats, while repeated treatment with progesterone elicits the opposite effect. Coadministration of testosterone and progesterone causes an intermediate effect such that the net result is an increase in expression only slightly above control levels. Interestingly, when ovariectomized female rats treated with testosterone and progesterone are used as a source of brain tissue for RNA preparation a similar trend toward an intermediate value is seen but the net result is an expression level of CYP2D below the control value. This approach utilizes cPCR to analyze the levels of CYP2D mRNA, semi-quantitatively and quantitatively, in the brains of female intact and ovariectomized Sprague-Dawley rats treated with testosterone, progesterone, a combination of the two or corn oil.