Rifampicin Transport by OATP1B1 Variants

Abstract

Single nucleotide polymorphisms in the OATP1B1 transporter have been suggested to partially explain the large interindividual variation in rifampicin exposure. HEK293 cells overexpressing wild-type (WT) or OATP1B1 variants *1b, *4, *5, and *15 were used to determine the in vitro rifampicin intrinsic clearance. For OATP1B1*5 and *15, a 36% and 42% reduction in intrinsic clearance, respectively, compared to WT was found. We consider that these differences in intrinsic clearance most likely have minor clinical implications.

Keywords: OATP1B1; SNP; drug transport; rifampicin.

FIG 1

(A and B) Concentration-dependent uptake curve for OATP1B1-mediated uptake of rifampicin (A) and corrected for transporter expression by Western blotting (B). The transport velocity was determined by examining the uptake of rifampicin in OATP1B1 WT, *1b, *4, *5, and *15. The OATP1B1 mediated transport was obtained by subtracting the transport velocity in vector-transduced cells from those in OATP1B1 WT or variant-expressing cells. Each point and bar represents the mean ± standard error of the mean from three independent experiments. The solid/dotted lines represent the fitted lines.

FIG 2

Quantification of OATP1B1 protein expression in HEK293 cells of one of the three independent experiments. Membrane fractions were obtained from HEK293 cells and separated by SDS-PAGE (4% to 20%). The applied amount of protein was 25 μg, and total protein staining (Ponceau) confirmed equal loading across the lanes. The OATP1B1 proteins were detected using a polyclonal anti-OATP2 antibody for OATP1B1 followed by an Alexa Fluor 680 goat anti-rabbit IgG antibody secondary antibody.