@article {CHUNG543, author = {LELAND W. K. CHUNG and HAIYEN CHAO}, title = {Neonatal Imprinting and Hepatic Cytochrome P-450 }, volume = {18}, number = {3}, pages = {543--549}, year = {1980}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {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{\textquoteright}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.}, issn = {0026-895X}, URL = {https://molpharm.aspetjournals.org/content/18/3/543}, eprint = {https://molpharm.aspetjournals.org/content/18/3/543.full.pdf}, journal = {Molecular Pharmacology} }