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 gluc uronide group from UDP-glucuronic acid to several exogenous or endogenous c ompounds, 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 ti ssues such as the prostate. Measurement of androgen metabolites in human pr ostate revealed high levels of C-19 steroid glucuronides such as androstero ne glucuronide and 3 alpha -diol glucuronide, thus suggesting an important role of UGT2B enzymes in androgen metabolism. To investigate the cellular l ocalization of UGT2B expression in the human prostate, the present in situ hybridization studies demonstrated the presence of UGT2B transcripts in epi thelial cells lining the acinii. All basal cells were intensively labeled, whereas the luminal secretory cells were moderately labeled. To confirm the se results, an immunohistological analysis was performed using a specific a nti-UGT2B antibody. The presence of UGT2B proteins was observed in both bas al and luminal cells of prostate epithelium, in fibrocytes of stroma and bl ood vessels, and in endothelial cells of blood vessels. Using a specific an ti-UGT2B17 antibody, the expression of this androsterone-conjugating UGT en zyme was found exclusively in basal cells of the epithelium. These results demonstrate the expression of androgen-conjugating UGT2B enzymes in human p rostatic epithelium. Moreover, they show for the first time a cell type-spe cific expression of an UGT2B isoform.