Sex Differences in the Constitutive Gene Expression of Sulfotransferases and UDP-glucuronosyltransferases in the Pig Liver: Androgen-mediated Regulation

Summary:Using two breeds (Meishan and Landrace) of pigs and their crossbred offspring (ML, Meishan χ Landrace; LM, Landrace χ Meishan), of which males have genetically different serum androgen levels, we examined whether or not serum androgen plays a crucial role in the constitutive gene expression of hepatic sulfotransferases (SULTs) and UDP-glucuronosyltransferases (UGTs). Real-time RT-PCR analyses showed that in Meishan, ML, and LM pigs, SULT1A1 and SULT2A1 mRNA levels were lower in males having high levels of serum androgen (> 38ng/ml) than in females, whereas those of UGT1A1, UGT1A6, and UGT2B31 were just the opposite. In Landrace pigs having low levels of serum androgen (< 22ng/ml), no such sex differences in expression levels were observed. Moreover, castration of male Meishan pigs altered the gene expression patterns of SULTs and UGTs to female levels. Testosterone-treatment to the castrated males and intact females of either pig breed resulted in decreased SULT1A1 and SULT2A1 and increased UGT1A1, UGT1A6, and UGT2B31 mRNA levels. These findings demonstrate that androgen is one of the physiological factors that determine sexual dimorphism on the constitutive gene expression of SULTs and UGTs in the pig liver.