Protein quality and urea kinetics in prepubertal Chilean schoolboys.
Urea kinetics were measured non-invasively in 12 Chilean schoolboys aged 8-10 years who were receiving one of two diets, either predominantly animal protein or predominantly vegetable protein. Both the diets provided an equivalent level of gross protein, 1.2 g/kg/day. The study diets were given for 10 days to enable adaptation to take place. On the eighth day a single oral dose of 15N15N-urea, 100 mg, was given and the amount of label excreted as 15N15-urea in urine over the subsequent 48 hours was measured. There was little difference in any aspect of urea kinetics between the two diets with urea production (animal, 173 +/- 50 mgN/kg/day; vegetable 179 +/- 53 mgN/kg/day), urea excretion (animal, 86 +/- 19 mgN/kg/day; vegetable, 105 +/- 13 mgN/kg/day), urea nitrogen hydrolysis (animal, 87 +/- 49 mgN/kg/day; vegetable, 74 +/- 42 mgN/kg/day), and the salvaged urea-nitrogen derived from hydrolysis which returned to urea formation (animal, 12 +/- 5 mgN/kg/day; vegetable, 17 +/- 9 mgN/kg/day) all being similar. A very high proportion of the salvage nitrogen derived from urea hydrolysis was maintained within the metabolic pool, about 80%, which was equivalent to 0.4 g protein/kg/day. This is the first time urea kinetics have been measured in children of this age and shows that 57% of the ura produced is excreted in urine on average with about 43% of the urea-nitrogen being salvaged for further metabolic interaction. It is concluded that the vegetable based protein diet taken habitually by Chilean children is metabolically equivalent in terms of urea kinetics to a diet based upon animal protein at this level of intake, but that high rates of salvage of urea nitrogen are found on both diets.
Bickerton
A S
AS
Department of Human Nutrition, University of Southampton, UK.
Birch
R
R
Jackson
A A
AA
Uauy
R
R
Persaud
C
C
Gattas
V
V
Barrera
G
G
D000375:Aging / Q000378:metabolism*; D001806:Blood Urea Nitrogen; D001827:Body Height / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002648:Child; D002677:Chile; D004044:Dietary Proteins / Q000494:pharmacology / Q000592:standards*; D006801:Humans; D006868:Hydrolysis; D008297:Male; D009584:Nitrogen / Q000378:metabolism / Q000652:urine; D011627:Puberty / Q000378:metabolism; D012885:Skinfold Thickness; D014508:Urea / Q000493:pharmacokinetics* / Q000652:urine
D004044:Dietary Proteins; D014508:Urea; D009584:Nitrogen