Bovine liver slices: A multifunctional in vitro model to study the prohormone dehydroepiandrosterone (DHEA)

Biotransformation of inactive prohormones like dehydroepiandrosterone (DHEA) can lead to the formation of potent androgens and subsequent androgenic responses in target tissues. In the present study, precision-cut bovine liver slices were used to study the effects of DHEA on the metabolite, transcript and androgenic activity level. Bovine liver slices were exposed for 6h to various concentrations of DHEA. Changes in androgenic activity of the DHEA containing cell culture media were measured using a yeast androgen bioassay and metabolites were identified using ultra performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOFMS), while gene expression in the DHEA-treated liver slices was examined using bovine microarrays and compared with the profile as obtained with 17ß-testosterone (17ß-T). An increase in androgenic activity was observed in the bioassay upon testing of samples from incubations of DHEA with liver slices and the formation of 4-androstenedione (4-AD), 5-androstene-3ß,17ß-diol, 17ß-T, 7α-hydroxy-DHEA, 7-keto-DHEA and 17α-T could be confirmed by UPLC-TOFMS analysis. Exposure of liver slices to DHEA and the strong androgen 17ß-T resulted in the identification of significantly up- and down-regulated genes and revealed similar gene expression profiles for both compounds. The results indicate that DHEA itself is biologically not very active, but is rapidly converted by the liver slices into the more androgen active compounds 4-AD and 17ß-T. Moreover, the present data highlight the multi-functionality of bovine liver slices as an in vitro bioactivation model, allowing the assessment of androgen activity or gene expression as effect-based endpoints for prohormone exposure.