TY - JOUR T1 - Neonatal Imprinting and Hepatic Cytochrome <em>P</em>-450 JF - Molecular Pharmacology JO - Mol Pharmacol SP - 543 LP - 549 VL - 18 IS - 3 AU - LELAND W. K. CHUNG AU - HAIYEN CHAO Y1 - 1980/11/01 UR - http://molpharm.aspetjournals.org/content/18/3/543.abstract N2 - Rat hepatic microsomal cytochrome P-450s were resolved by DEAE-cellulose column chromatography. A comparison was made between the elution profiles of the cytochrome P-450 from the neonatally imprinted (adult male and adult male castrated at 4 weeks of age) and nonimprinted (adult female and adult male castrated at birth) rats. Four peaks of cytochrome P-450 (designated peaks I, II, III, and IV) were eluted by a linear salt gradient from 0 to 0.25 M NaCl. No consistent qualitative difference was found in the elution profiles of cytochrome P-450 from the solubilized microsomes of these rats. However, further resolution of the catalytic activities of the various peaks of cytochrome P-450 in a reconstituted system revealed a form or forms of cytochrome P-450 in the peak II fraction that can be imprinted by gonadal hormones during the neonatal period. Only the form of cytochrome P-450 isolated from the neonatally imprinted animals was capable of hydroxylating testosterone at the 16α position to a significant degree similar to that reported for the intact microsomes. Phenobarbital treatment enhanced the total as well as the various peaks of cytochrome P-450 content in the hepatic microsomes of both adult male and female rats. Cytochrome P-450 content in peak III/IV, however, was differentially induced by the phenobarbital treatment. This differentially induced form or forms of cytochrome P-450 hydroxylated testosterone in a reconstituted system at the 16α but not at the 7α or 6β positions. ACKNOWLEDGMENTS This study was formulated during LWKC’s tenure at McGill University. The excellent secretarial help from Ms. Pamela Lingenfelter and the critical reading of the manuscript by Dr. Richard J. Kraemer are appreciated. ER -