Cortisol metabolism and its inhibition by glycyrrhetinic acid in the isolated perfused human placental lobule.

We have previously reported the placental metabolism of prednisolone to prednisone, 20alpha- and beta-dihydroprednisone and 20beta-dihydroprednisolone. In this study, the disposition of cortisol was investigated in vitro in the dual perfused, isolated human placental lobule after the addition of cortisol (1.2 micromol, n = 3 and 12 micromol, n = 4) to the maternal compartment. Analysis of 5 h maternal and fetal perfusate samples by high performance liquid chromatography-electrospray-tandem mass spectrometry (HPLC-ESI-MS/MS) revealed that cortisol was mainly metabolized to cortisone, but a significant production of 20alpha-dihydrocortisone, 20beta-dihydrocortisone, 20alpha-dihydrocortisol and 20beta-dihydrocortisol was also detected. Saturability of metabolism but not transfer was demonstrated. Metabolism was eliminated by co-perfusion with the potent 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzyme inhibitor 18beta-glycyrrhetinic acid (GA). The disposition of GA was analysed using HPLC-atmospheric pressure chemical ionisation-MS/MS (HPLC-APCI-MS/MS). GA was found to transfer from the maternal to the fetal circulations without detectable metabolism during 6 h of perfusion.