Measurement of transport activities of bile acids in human multidrug resistance-associated protein 3 using liquid chromatography-tandem mass spectrometry.

A method has been developed for the measurement of transport activities in membrane vesicles obtained from human multidrug resistance-associated protein 3-expressing Sf9 cells for 1 beta-hydroxy-, 6 alpha-hydroxy- and unsaturated bile acids by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. Calibration curves for the bile acids were linear over the range of 10 to 2000 pmol/mL, and the detection limit was less than 2 pmol/mL for all bile acids using selected reaction monitoring analysis. The method was applied to measurements of adenosine triphosphate-dependent transport activities of the membrane vesicles for the above-mentioned hydroxylated and unsaturated bile acids. The present study demonstrated that the human multidrug resistance-associated protein 3 vesicles accepted 1 beta-, 6 alpha-hydroxylated and unsaturated bile acids along with common bile acids, such as glycocholic acid and taurolithocholic acid 3-sulfate. The developed method is useful for measurements of bile acid transport activities.