Arginine therapy of argininosuccinase deficiency

Argininosuccinic acid (A.S.A.) contains the two waste nitrogen atoms later excreted in urea in healthy people, and it has a renal clearance similar to the glomerular filtration-rate. Therefore, argininosuccinic acid might provide a vehicle for the excretion of waste nigrogen in patients with argininosuccinase deficiency, providing that stoichiometric amounts of ornithine are available. When two infants with no, or very little, erythrocyte argininosuccinase activity who were in neonatal hyperammonaemic coma were treated with supplementary arginine (4-5 mmol/kg/day) plasma ammonium, glutamine, and alanine concentrations became normal. One infant grew and developed normally during the first month of life on a protein intake of 2 g/kg/day. The other infant had sustained lathal brain damage before arginine therapy was tried and she died aged 17 days. Arginine supplementation may be effective therapy for argininosuccinase deficiency because it promotes A.S.A. synthesis and hence excretion of waste nitrogen. The effects of high plasma-A.S.A. concentrations are unknown.