Measurement of urinary total 13C and 13C urea by isotope ratio mass spectrometry after administration of lactose [13C]-Ureide

✍ Scribed by Douglas J. Morrison; Brian Dodson; Tom Preston

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 90 KB
• Volume: 13
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(19990715)13:13<1252::aid-rcm565>3.0.co;2-j

✦ Synopsis

A method of measuring total 13 C excreted in urine after oral administration of lactose [ 13 C]-ureide was developed using isotope ratio mass spectrometry. Furthermore, a method to measure 13 C urea excreted in the urine was developed. Each urine sample collected over a 24 hour period, after administration of the tracer dose, was analysed for both total 13 C and 13 C urea. Combustion of the dried urine samples allowed measurement of the total 13 C content. Treatment of urine samples with urease (EC 3.5.1.5) and analysis by isotope ratio mass spectrometry of the CO 2 evolved allowed measurement of 13 C urea in the urine sample. The total 13 C and 13 C urea contents of each urine sample, obtained throughout the protocol, were compared to total 13 C and 13 C urea contents of a urine sample taken before the test. This allowed calculation of the fraction of tracer incorporated into urea and the fraction of tracer excreted in total. Analyses showed that approximately 15% of the dose administered, in terms of 13 C, was recovered in the urine over the sampling period. Further analysis for urinary 13 C urea showed that less than 1% of the label was incorporated into urea excreted over the sampling period.