DETERMINATION OF TAURINE METABOLISM BY MEASUREMENT OF N-15-ENRICHED TAURINE IN CAT URINE BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

To understand the biological function of taurine, a study of taurine k inetics in the cat was undertaken. This paper describes a method devel oped for the accurate determination of N-15-taurine enrichment in cat urine by gas chromatography-mass spectrometry. N-15-Taurine was given to six animals as an oral bolus dose of 20 mg/kg body weight, and the urine was pooled on a daily basis. The hydrolysed or non-hydrolysed ur ine samples (for total and free taurine, respectively) were directly d erivatized without further purification. The N-pentafluorobenzoyl di-n -butyl amide derivative obtained was analysed, and the fragment [M-(di -n-butyl amide)]+, carrier of the labelled nitrogen atom, was selectiv ely recorded at m/z 302 (N-14-taurine) and m/z 303 (N-15-taurine). Cal ibration curves prepared in hydrolysed and non-hydrolysed urine sample s spiked with N-15-taurine gave similar slopes to the calibration curv e prepared in water. The average coefficient of variation observed for the mole percent excess in the non-hydrolysed samples was 1.22% (n = 92) and for the hydrolysed urine 1.00% (n = 98). There was no signific ant difference between free and total taurine enrichment. The half-lif e of taurine in cat body was found to be 29.3 +/- 2.9 h and 35.0 +/- 1 .4 h for free and total taurine, respectively (non-significant). The t aurine body pool, calculated by extrapolation of the curve to zero tim e, had a value of 137 +/- 22 ng/kg and 157 +/- 11 mg/kg for free and t otal taurine, respectively.