Comparative uptake of statins by hepatic organic anion transporting polypeptides

Uptake into hepatocytes by the organic anion transporting polypeptides (OATP) 1B1, 1B3, and 2B1 can form a rate-determining step in drug clearance. While several lipid-lowering statin drugs are substrates of the hepatic OATPs, the literature statin uptake profiles form a wide range with values obtained from different laboratories and systems. Therefore, this study aimed to characterize hepatic OATP-mediated transport of statins in a single-laboratory experimental setup, allowing comparison between the statins and OATPs. The uptake of atorvastatin, 3R,5S-fluvastatin, 3S,5R-fluvastatin, pravastatin, rosuvastatin, and simvastatin acid was assessed in human embryonic kidney 293 cells overexpressing OATP1B1, 1B3, or OATP2B1. All the three OATPs transported atorvastatin with K_m values 2.6 μM (1B1), 1.9 μM (1B3), and 1.1 μM (2B1). Also rosuvastatin was transported by all the OATPs: OATP1B1 (as previously reported from our lab) and 2B1 affinities were similar (13 μM) while OATP1B3 had a K_m of 40 μM. Although all OATPs also transported pravastatin, the uptake by OATP2B1 was not saturated at the studied concentration range, and affinity parameters could be determined only for OATP1B1 and 1B3 at K_m 37 μM and 28 µM, respectively. OATP2B1 was the high-affinity transporter of the fluvastatin enantiomers (K_m 0.57 μM for 3S,5R- and 2.5 μM for 3R,5S-fluvastatin) which were not taken up by OATP1B3. Importantly, active simvastatin acid uptake was observed only for OATP1B1 with a K_m value of 2.1 μM. Taken together, only OATP1B1 could transport all statins and, in general, the affinities of the hydrophobic statins (atorvastatin, fluvastatin, simvastatin acid) were higher compared to the hydrophilic statins (pravastatin, rosuvastatin). These differences between the OATPs and statins can help to explain differences in clinically observed statin gene-drug interactions and have utility in the pharmacokinetic modeling of statins.