title: Characteristics of NO cycle coupling with urea cycle in non-hyperammonemic carriers of ornithine transcarbamylase deficiency.
abstract: Urea cycle deficient patients with prominent hyperammonemic often exhibit abnormal production of nitric oxide (NO), which reduces vascular tone, along with amino acid abnormalities. However, information related to the metabolic changes in heterozygotes of ornithine transcarbamylase deficiency (OTCD) lacking overt hyperammonemia is quite limited. We examined vascular mediators and amino acids in non-hyperammonemic heterozygotes. Twenty-four heterozygous OTCD adult females without hyperammonemic bouts, defined as non-hyperammonemic carriers, were enrolled. We measured blood amino acids constituting urea cycle and nitric oxide (NO) cycle. Blood concentrations of nitrate/nitrite (NOx) as stable NO-metabolites, asymmetric dimethylarginine (ADMA) inhibiting NO synthesis, and endothelin-1 (ET-1) raising vascular tone were also determined. NOx concentrations were significantly lower in non-hyperammonemic carriers (p < 0.01). However, ADMA and ET-1 levels in this group were comparable to those in the age-matched control group. Arginine and citrulline levels were also significantly lower in non-hyperammonemic carriers than in controls (p < 0.01). Of the 24 non-hyperammonemic carriers, 10 often developed headaches. Their daily NOx and arginine levels were significantly lower than those in headache-free carriers (p < 0.05). In three carriers receiving oral l-arginine, blood NOx concentrations were significantly higher. In two of those three, the occurrence of headaches was decreased. These results suggest that NO cycle coupling with the urea cycle is altered substantially even in non-hyperammonemic OTCD carriers, predisposing them to headaches.
authors.affiliation: Department of Pediatrics, Takarazuka City Hospital, 4-5-1 Kohama-cho, Takarazuka 665-0827, Japan. nagasa-hirono@k2.dion.ne.jp
authors.forename: Hironori
authors.initials: H
authors.lastname: Nagasaka
authors.forename: Tohru
authors.initials: T
authors.lastname: Yorifuji
authors.forename: Hiroto
authors.initials: H
authors.lastname: Egawa
authors.forename: Ayano
authors.initials: A
authors.lastname: Inui
authors.forename: Tomoo
authors.initials: T
authors.lastname: Fujisawa
authors.forename: Haruki
authors.initials: H
authors.lastname: Komatsu
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Tsukahara
authors.forename: Shinji
authors.initials: S
authors.lastname: Uemoto
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Inomata
mesh_terms: D000596:Amino Acids / Q000097:blood; D000641:Ammonia / Q000097:blood; D002675:Child, Preschool; D019332:Endothelin-1 / Q000097:blood; D005260:Female; D006579:Heterozygote; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D053858:Metabolic Networks and Pathways; D009569:Nitric Oxide / Q000378:metabolism*; D020163:Ornithine Carbamoyltransferase Deficiency Disease / Q000235:genetics* / Q000378:metabolism*; D014508:Urea / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D019332:Endothelin-1; D009569:Nitric Oxide; D000641:Ammonia; D014508:Urea