title: A noninvasive method for measuring urea kinetics with a single dose of [15N15N]urea in free-living humans.
abstract: A noninvasive method is described in which the endogenous rate of urea production can be determined in normal, free-living adults. A single dose of [15N15N]urea was given orally, and the amount of label excreted as [15N15N]urea and [15N14N]urea in urine over the subsequent 48 h was measured. From the rates of excretion of labeled and unlabeled urea the rate of urea production was derived. Using this single-dose protocol the rate of urea production was 207 +/- 56 (mean +/- SD) mg N/(kg.d) in six normal adult men consuming 74 g protein/d. These results were not different when compared with rates of urea production obtained with a prime/intermittent protocol in an earlier study in the same individuals [199 +/- 20 mg N/(kg.d)]. We conclude that urea kinetics can be measured noninvasively with a single dose of [15N15N]urea and that this method may be suitable for use in free-living individuals to determine urea production rates for habitual dietary intakes.
authors.affiliation: Department of Human Nutrition, University of Southampton, U.K.
authors.forename: A A
authors.initials: AA
authors.lastname: Jackson
authors.forename: M S
authors.initials: MS
authors.lastname: Danielsen
authors.forename: S
authors.initials: S
authors.lastname: Boyes
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000641:Ammonia / Q000652:urine; D006801:Humans; D008297:Male; D009587:Nitrogen Isotopes; D010865:Pilot Projects; D013997:Time Factors; D014508:Urea / Q000008:administration & dosage / Q000378:metabolism / Q000652:urine*
chemical_list: D009587:Nitrogen Isotopes; D000641:Ammonia; D014508:Urea