Glucocorticoid receptor is involved in the breed-dependent transcriptional regulation of 3[beta]-hydroxysteroid dehydrogenase in the liver of preweaning piglets

Background Hepatic 3[beta]-hydroxysteroid dehydrogenase (3[beta]-HSD) plays an important role in steroid inactivation and catabolism. Serum concentrations of steroid hormones differ significantly between breeds in pigs, however the molecular mechanism regulating hepatic 3[beta]-HSD expression in different breeds of pigs is poorly understood. In the present study, we used preweaning purebred male Large White (LW) and Erhualian (EHL) piglets as model to investigate the breed difference in the expression and regulation of 3[beta]-HSD gene in porcine liver. Results The hepatic expression of 3[beta]-HSD mRNA was significantly lower (P < 0.01) in EHL piglets compared to that in LW piglets. Significant breed differences were detected for the hepatic expression of transcription factors such as androgen receptor (AR), glucocorticoid receptor (GR), and CCAAT/enhancer binding protein [beta] (C/EBP[beta]). The nucleoprotein contents of AR (P < 0.05), GR (P < 0.01) and phospho-Ser.sup.211GR (P < 0.01) were significantly higher in the liver of EHL piglets. Chromatin immunoprecipitation (ChIP) assay demonstrated significantly lower binding of GR, but not AR or C/EBP[beta], to 3[beta]-HSD gene promoter in EHL piglets (P < 0.05). GR was not detected to interact with C/EBP[beta] or AR in the co-immunoprecipitation analysis. Conclusions These results indicate that GR binding to 3[beta]-HSD promoter is involved in the breed-dependent 3[beta]-HSD expression in the liver of piglets. Keywords: AR, C/EBP[beta], GR, Liver, Pig, 3[beta]-HSD