A noninvasive method for measuring urea kinetics with a single dose of [15N15N]urea in free-living humans
Jackson, A.A.; Danielsen, M.S.; Boyes, S.
Journal of Nutrition 123(12): 2129-2136
1993
ISSN/ISBN: 0022-3166 PMID: 8263607 Document Number: 408501
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 (15N-15N)urea was given orally, and the amount of label excreted as (15N-15N)urea and (15N-14N)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 cntdot 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 cntdot d)). We conclude that urea kinetics can be measured noninvasively with a single dose of (15N-15N)urea and that this method may be suitable for use in free-living individuals to determine urea production rates for habitual dietary intakes.