We have previously demonstrated differences between Meishan and Landrace pigs in their serum androgen levels (Meishan > Landrace) and the expression of genes encoding hepatic cytochrome P450 (CYP) 1A subfamily enzymes (Meishan < Landrace). In the present study, to clarify whether such differences are genetically controlled, we crossbred these pigs (female Meishan x male Landrace, ML; female Landrace x male Meishan, LM) and examined the expression levels of serum androgen and hepatic CYP family genes (CYP1A1, CYP1A2, CYP2A19, and CYP2E1) among ML, LM, and their parents. In sexually mature (5-month-old) male ML or LM pigs, not only the serum androgen level, but also the hepatic expression levels of all the CYPs examined were similar to those in male Meishan pigs. In addition, there were few breed differences among the females of Meishan, Landrace, ML and LM pigs in the expression of all the CYP genes examined. Furthermore, the expression levels of these CYPs in the females of Meishan and Landrace pigs could be decreased to the corresponding levels in male Meishan pigs by administration of testosterone propionate. The present findings demonstrate that serum androgen level is determined by autosomal dominant inheritance and that the level of serum androgen is one of the host factors regulating the constitutive expression of CYP1A1, CYP1A2, CYP2A19, and CYP2E1 in the pig liver. (C) 2012 Elsevier Inc. All rights reserved.