Abstract
It has been suggested that lysine inhibits urea cycle function both in vivo and in vitro mainly by decreasing arginase activity. We gave an L-alanine load to a patient with hyperlysinemia (fasting plasma lysine 860 μM on a 1.5 g protein/kg diet) at age 5 and 10 years, and to a patient with saccharopinuria (and hyperlysinemia) at age 3, 12.5 and 16 years. The alanine was given as a 5% aqueous i.v. infusion (6.6 mmol/kg) over 90 min and changes in blood ammonia, serum urea urinary orotic acid were measured.
In healthy subjects, serum urea increases rapidly, but blood ammonia and urinary orotic acid remain unchanged after such a load. The patient with hyperlysinemia developed hyperammonemia (peak values 760 and 210 μM at 5 and 10 years of age), and orotic aciduria increased 10-fold in the first 6-h collection. Serum urea increased slowly. The saccharopinuric patient's peak ammonias were 60, 280 and 410 μM at 3, 12.5 and 16 years of age, respectively; serum urea increased always slowly. Orotic acid excretion in the latest test increased 320-fold. Addition of 1.1 mmol/kg of l-ornithine to the alanine loads abolished the hyperammonemic response totally in both, and urinary orotic acid increased only 2-3 fold. The findings suggest that patients with constant hyperlysinemia or with saccharopinuria have decreased nitrogen tolerance and may benefit from ornithine supplementation.
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Simell, O., Luukkainen, P. & Sipilä, I. 1260 ALANINE-INDUCED HYPERAMMONEMIA IN HYPERLYSINEMIA AND IN SACCHAROPINURIA. Pediatr Res 19, 320 (1985). https://doi.org/10.1203/00006450-198504000-01290
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DOI: https://doi.org/10.1203/00006450-198504000-01290
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