Glycocholic acid-d4 is intended for use as an internal standard for the quantification of glycocholic acid by GC- or LC-MS. Glycocholic acid is a glycine-conjugated form of the primary bile acid cholic acid and has roles in the emulsification of fats.1,2 It reduces expression of the gene encoding the farnesoid X receptor (FXR) and increases expression of the genes encoding the bile acid receptors TGR5 and S1PR2 in SNU-245 cells when used at a concentration of 1.6 μmol/ml.3 Glycocholic acid (250 μM) increases the intracellular accumulation and cytotoxicity of epirubicin in Caco-2 cells, as well as decreases expression of the genes encoding multidrug resistance protein 1 (MDR1), MDR-associated protein 1 (MRP1), and MRP2 when used alone or in combination with epirubicin.4 It increases absorption of epirubicin into everted sacs of rat ileum and jejunum when used at a concentration of 250 μM. The bile acid composition ratio of glycocholic acid is elevated in bile of patients with cholangiocarcinoma compared with patients with pancreatic cancer or benign biliary diseases.3 Serum levels of glycocholic acid are elevated in patients with hepatocellular carcinoma compared with healthy individuals.2

1.Lefebvre, P., Cariou, B., Lien, F., et al.Role of bile acids and bile acid receptors in metabolic regulationPhysiol. Rev.89(1)147-191(2009) 2.Guo, C., Xie, C., Ding, P., et al.Quantification of glycocholic acid in human serum by stable isotope dilution ultra performance liquid chromatography electrospray ionization tandem mass spectrometryJ. Chromatogr. B. Analyt. Technol. Biomed. Life Sci.1072315-319(2018) 3.Song, W.-S., Park, H.-M., Ha, J.M., et al.Discovery of glycocholic acid and taurochenodeoxycholic acid as phenotypic biomarkers in cholangiocarcinomaSci. Rep.8(1)11088(2018) 4.Lo, Y.L., Ho, C.T., and Tsai, F.L.Inhibit multidrug resistance and induce apoptosis by using glycocholic acid and epirubicinEur. J. Pharm. Sci.35(1-2)52-67(2008)