Previously, the steroid hormone progesterone has been demonstrated to stimulate OATP2B1-mediated transport of estrone-3-sulphate (E(1)S), dehydroepiandrosterone sulphate (DHEAS) and pregnenolone sulphate (PS), which may influence the uptake of precursor molecules for steroid hormone synthesis. However, it is unclear whether OATP2B1 drug substrates like atorvastatin or glibenclamide are also affected by this phenomenon. In addition, it has not been studied so far if this stimulatory effect is specific for OATP2B1. To address these questions, we examined the influence of progesterone on OATP2B1-mediated atorvastatin and glibenclamide uptake and studied the impact of steroid hormones on the transport activity of OATP1A2, OATP1B1 and OATP1B3. Comparison of the substrate spectrum of the investigated OATPs revealed that DHEAS and atorvastatin are substrates of all transporters, while E(1)S was only significantly transported by OATP1A2, OATP2B1 and OATP1B1. Glibenclamide uptake was limited to OATP1A2, OATP1B1 and OATP2'B1. Subsequent interaction studies indicated that progesterone only increases OATP2B1-mediated E(1)S and DHEAS transport, whereas uptake of BSP, atorvastatin and glibenclamide was either inhibited or not affected. Moreover, the steroid hormone effect was specific for OATP2B1; neither OATP1B1, OATP1B3 nor OATP1A2 function was stimulated in the presence of progesterone. Similar to progesterone, the glucocorticoide dexamethasone stimulated OATP2B1-mediated transport of E(1)S and DHEAS (EC(50) for E(1)S: 10.2 ± 5.6 μM and 17.9 ± 15.4 μM for DHEAS). In conclusion, our data demonstrate that among the tested compounds the stimulatory effect of progesterone is specific for OATP2B1 and restricted to sulphated steroids like E(1)S and DHEAS while the OATP-mediated drug transport is not enhanced.
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