A Comparison of Total and Plasma Membrane Abundance of Transporters in Suspended, Plated, Sandwich-Cultured Human Hepatocytes vs. Human Liver Tissue Using Quantitative Targeted Proteomics and Cell-Surface Biotinylation.

Suspended (SH), plated (PH) and sandwich-cultured hepatocytes (SCH) are commonly used models to predict in vivo transporter-mediated hepatic uptake (SH or PH) or biliary (SCH) clearance of drugs. When doing so, the total and plasma membrane abundance (PMA) of the transporter is assumed not to differ between hepatocytes and liver tissue (LT). This assumption has never been tested. Here, we tested this assumption by measuring the total and PMA of transporters in human hepatocyte models vs. LT (total only) from which they were isolated. Total abundance of OATP1B1/2B1/1B3, OCT1, and OAT2 was not significantly different between the hepatocytes and LT. The same was true for the PMA of these transporters across the hepatocyte models. In contrast, total abundance of the sinusoidal efflux transporter, MRP3, and the canalicular efflux transporters, MRP2 and P-gp, was significantly greater (P<0.05) in SCH vs. LT. Of the transporters tested, only the percent PMA of OATP1B1, P-gp and MRP3, in SCH (82.8±7.3%, 57.5±10.9%, 69.3±5.7%) was significantly greater (P<0.05) than in SH (73.3 ±6.4%, 27.4±6.4%, 53.6±4.1%). If the transporters measured in the plasma membrane are functional and the PMA in SH is representative of that in LT, these data suggest that SH, PH, and SCH will result in equal prediction of hepatic uptake clearance of drugs mediated by the transporters tested above. However, SCH will predict higher sinusoidal efflux and biliary clearance of drugs if the change in PMA of these transporters is not taken into consideration.