Cellular localization of uridine diphosphoglucuronosyltransferase 2B enzymes in the human prostate by in situ hybridization and immunohistochemistry.

UDP-glucuronosyltransferase (UGT) enzymes catalyze the transfer of the glucuronide group from UDP-glucuronic acid to several exogenous or endogenous compounds, including steroid hormones. Although it is widely recognized that the liver is a major site of steroid glucuronidation, RT-PCR analysis has shown the expression of UGT2B transcripts in extrahepatic steroid target tissues such as the prostate. Measurement of androgen metabolites in human prostate revealed high levels of C(19) steroid glucuronides such as androsterone glucuronide and 3alpha-diol glucuronide, thus suggesting an important role of UGT2B enzymes in androgen metabolism. To investigate the cellular localization of UGT2B expression in the human prostate, the present in situ hybridization studies demonstrated the presence of UGT2B transcripts in epithelial cells lining the acinii. All basal cells were intensively labeled, whereas the luminal secretory cells were moderately labeled. To confirm these results, an immunohistological analysis was performed using a specific anti-UGT2B antibody. The presence of UGT2B proteins was observed in both basal and luminal cells of prostate epithelium, in fibrocytes of stroma and blood vessels, and in endothelial cells of blood vessels. Using a specific anti-UGT2B17 antibody, the expression of this androsterone-conjugating UGT enzyme was found exclusively in basal cells of the epithelium. These results demonstrate the expression of androgen-conjugating UGT2B enzymes in human prostatic epithelium. Moreover, they show for the first time a cell type-specific expression of an UGT2B isoform.