Deregulated Hepatic Metabolism Exacerbates Impaired Testosterone Production in Mrp4‐Deficient Mice

Abstract

The physiological role of multidrug resistance protein 4 (Mrp4, Abcc4) in the testes is unknown. We found that Mrp4 is expressed primarily in mouse and human Leydig cells; however, there is no evidence that Mrp4 regulates testosterone production. We investigated its role in the Leydig cells, where testosterone production is regulated by cAMP, an intracellular messenger formed when the luteinizing hormone (LH) receptor is activated. Because Mrp4 regulates cAMP, we compared testosterone levels in Mrp4−/− and Mrp4+/+ mice. Young Mrp4−/− mice had significantly impaired gametogenesis, reduced testicular testosterone, and disruption of Leydig‐cell cAMP homeostasis. Both young and adult mice had impaired testosterone production. In Mrp4−/− primary Leydig cells treated with LH, intracellular cAMP production was impaired and CREB phosphorylation was strongly attenuated. Notably, expression of CREB target genes that regulate testosterone biosynthesis was reduced in Mrp4−/− Leydig cells in vivo. Therefore, Mrp4 is required for normal Leydig‐cell testosterone production. However, adult Mrp4−/− mice are fertile with a normal circulating testosterone concentration. The difference is in 3‐wk Mrp4−/− mice, disruption of gonadal testosterone production upregulates hepatic Cyp2b10, a known testosterone‐metabolizing enzyme. Therefore, defective testicular testosterone production deregulates hepatic Cyp‐mediated testosterone metabolism to disrupt gametogenesis. These findings have important implications for understanding the side‐effects of therapeutics that disrupt Mrp4 function and are reported to alter androgen production. This work was supported by grants from the NIH and ALSAC.