Simultaneous determination of cholic acid and chenodeoxycholic acid pool sizes and fractional turnover rates in human serum using

A method has been developed for simultaneous determination of pool sizes and fractional turnover rates (FTR) of chenodeoxycholic acid (CDCA) and cholic acid (CA) in man by "C/"C isotope ratio measurements of bile acids in serum after oral administration of 20-50 mg of [24-"CC]-labeled bile acids. "CC/"C isotope ratio measurements were performed by capillary gas-liquid chromatography/electron impact mass spectrometry. CA and CDCA kinetics in serum measured by this method exhibited first order kinetics and permitted calculation of pool size and FTR of CA and CDCA. T h e validity of the measurements in serum was tested by simultaneous measurements in bile in three healthy volunteers and in five patients with various hepatobiliary disorders (three patients with cirrhosis, one with cholecystectomy and sphincterotomy, and one with sphincterotomy only). No consistent differences were found between the pool sizes and FTR's obtained from serum and bile. In a total of five healthy volunteers bile acid kinetics were measured in serum. T h e values found for the pool sizes and FTR's of CA and CDCA in these subjects were in excellent agreement with data reported in the literature based on "C or 'H measurements in bi1e. l T h e pool sizes (mean +SD) of CDCA and CA were 32.6 f 9.9 and 31.8 f 16.0 I.cmol* kg-I, respectively. T h e corresponding values for the FTR's were 0.24 f 0.13 and 0.48 f 0.22 d-I. These data demonstrate that pool sizes and fractional turnover rates of cholic and chenodeoxycholic acid can be measured simultaneously by blood sampling after oral administration of the respective "C-labeled bile acids.-Stellaard, F., M. Sackmann, T. Sauerbruch, and G. Paumgartner. Simultaneous determination of cholic acid and chenodeoxycholic acid pool sizes and fractional turnover rates in human serum using "C-labeled bile acids. J. Liprd Res. 1984. 45: 13 13-1 3 19. Supplementary key wo& mass spectrometry capillary gas-liquid chromatography Measurements of pool size and fractional turnover rate (FTR) of the primary bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA) in man have been carried out by many investigators using the isotope dilution technique introduced by Lindstedt in 1957 (1). For this purpose a tracer dose of 14Cor 'H-labeled bile acids is administered intravenously or orally and the exponential decay of the specific activity is measured in duodenal bile samples collected daily for up to 9 days. In order to modify the method for studies in pregnancy (2) and newborns (3,4), Klein and co-workers introduced stable isotope labeled "C and 2H bile acids and the measurement of isotope ratios in bile. These measurements were carried out with gas-liquid chromatographymass spectrometry-isotope ratiometry. A Stable Isotope Ratiometer Multiple Ion Detector (SIRMID) was deveioped in order to monitor the "C and 12C isotopes and accurately measure the isotope ratios after subtraction of background noise (5). Isobutane-chemical ionization mass spectrometry was used for the fragmentation of methyl ester acetate derivatives (6). DeMark and his colleagues (7, 8) finally described a modified method for measurement of isotope ratios of bile acids in serum using NH3-chemical ionization. The application, however, was limited to the measurement of natural abundance. So far, only abstracts have appeared, describing the measurement of serum kinetics of CDCA (9, 10) and CA (1 1) in small numbers of patients and no reports of simultaneous determination of CDCA and CA kinetics in serum have been published. Moreover, only limited data (9, 11) exist on the comparison of the bile acid kinetics measured in serum with the kinetics measured in bile. Recently, a method for 1sC/'2C isotope ratio measurements of CDCA in serum by capillary gas-liquid chromatography and electron impact mass spectrometry has been developed in our laboratory (1 2) and has now been adjusted for simultaiieous measurements of CDCA Abbreviations: FTR, fractional turnover rate; CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxycholic acid; El. electron impact; TMS, trimethylsilyl; GLC, gas-liquid chromatography. Joumd of Lipid Remearch Volume 25, 1984 1313 at P E N N S T A T E U N IV E R S IT Y , on F ebuary 3, 2013 w w w .j.org D ow nladed fom and CA kinetics. The measurements of the pool sizes and FTR’s by this method in serum were validated against simultaneous measurements in bile in healthy volunteers and in patients with various hepatobiliary disorders. This comparison not only tests the validity of the measurements, but also proves that, in healthy subjects and in patients with cholecystectomy, sphincterotomy, or cirrhosis, the bile acids in the systemic and the enterohepatic circulation are in equilibrium. MATERIALS AND METHODS