Abstract
Extract: The excretion of 15N in the urine following the oral administration of compounds labeled with 15N was evaluated in an infant with congenital hyperammonemia while the infant was receiving a low protein diet. When she received either 15N-glycine or 15NH4Cl, the ratio of [15N-NH3] to [15N-urea] in urine was strikingly elevated with respect to [15N-NH3]/[15N-urea] found in studies of other infants receiving high protein diets. However, reduction of the protein in the diet of the control infants resulted in elevation of the ratio of [15N-NH3] to [15N-urea] in urine after the administration of 15N-glycine or 15NH4Cl. No mode of metabolism specific for congenital hyperammonemia was demonstrated in the studies of orally administered 15NH4Cl. In the metabolism of 15N-glycine, the hyperammonemic infant receiving a low protein diet was different from other infants on both high and low protein diets.
In the hyperammonemic infant, 15N-urea was much more readily formed from 15N-citrulline than from 15NH4Cl. On the other hand, the addition of unlabeled citrulline to the diet of this infant did not enhance the synthesis of 15N-urea from ingested 15NH4Cl when compared with the addition of unlabeled ornithine-HCl to the diet.
Speculation: The data presented lead to the conjecture that inborn errors of ammonia detoxification which result in clinical disease in surviving patients are “partial” defects, and that “complete” defects in ammonia detoxification are so rapidly lethal as to be seldom recognized clinically.
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Nicholson, J., Freeman, J. Metabolism of Compounds Labeled with 15N by an Infant with Congenital Hyperammonemia. Pediatr Res 6, 252–260 (1972). https://doi.org/10.1203/00006450-197204000-00007
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DOI: https://doi.org/10.1203/00006450-197204000-00007
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