Simultaneous determination of pool sizes and fractional turnover rates, of deoxycholic acid, cholic acid and chenodeoxycholic acid in man by isotope dilution with 2H and 13C labels and serum sampling.
This paper describes a method for simultaneous determination of the kinetics of the three major bile acids in man using (2,2,4,4-2H4) deoxycholic acid, (24-13C) cholic acid and (24-13C) chenodeoxycholic acid. The gas chromatographic/mass spectrometric-selected ion monitoring technique used provided complete separation of deoxycholic acid, cholic acid and chenodeoxycholic acid, which permitted simultaneous measurement of isotope ratios for all three bile acids. Since measurement of all three pool sizes and fractional turnover rates in a single experiment requires different isotopic labels for deoxycholic acid and cholic acid, we investigated the in vivo stability and applicability of (2,2,4,4-2H4) deoxycholic acid as a stable isotope marker for isotope dilution studies in man. No consistent differences were observed between deoxycholic acid pool sizes and fractional turnover rates determined in serum samples after administration of (2,2,4,4-2H4) deoxycholic acid and (24-13C) deoxycholic acid. Simultaneous administration of (2,2,4,4-2H4) deoxycholic acid, (24-13C) cholic acid and (24-13C) chenodeoxycholic acid and isotope ratio measurements in serum permitted determination of pool sizes and fractional turnover rates of the three major bile acid and the 7 alpha-dehydroxylation fraction. Pool sizes, fractional turnover rates and synthesis rates (input rates) agreed well with data obtained previously with (24-13C) labels in independent studies.
D002247:Carbon Isotopes; D002635:Chenodeoxycholic Acid / Q000097:blood / Q000378:metabolism*; D019826:Cholic Acid; D002793:Cholic Acids / Q000097:blood / Q000378:metabolism*; D003840:Deoxycholic Acid / Q000097:blood / Q000378:metabolism*; D003903:Deuterium; D006801:Humans; D007553:Isotope Labeling; D007700:Kinetics; D013058:Mass Spectrometry / Q000379:methods*; D011865:Radioisotope Dilution Technique; D012016:Reference Values
D002247:Carbon Isotopes; D002793:Cholic Acids; D003840:Deoxycholic Acid; D002635:Chenodeoxycholic Acid; D003903:Deuterium; D019826:Cholic Acid