Decreased transport of ornithine across the inner mitochondrial membrane as a cause of hyperornithinaemia.
Hyperornithinaemia due to a transport of ornithine across the inner mitochondrial membrane was demonstrated in three patients by measuring ornithine uptake by fibroblast mitochondria. Particulate compartments and soluble cytoplasm of fibroblasts were separated by a slight modification of the digitonin method of Zuurendonk and Tager. Patients' fibroblast pellet fraction contained significantly less radioactivity than control fibroblast pellet fraction after incubation of fibroblasts with [14C]-ornithine. Since neither of the patients was deficient in ornithine-delta-oxoacid aminotransferase, we concluded that in these hyperornithinaemia patients a defect exists for transport of ornithine across the inner mitochondrial membrane. The exact nature of this transport defect remains to be elucidated.
D000592:Amino Acid Metabolism, Inborn Errors / Q000097:blood*; D000596:Amino Acids / Q000097:blood; D001692:Biological Transport; D002675:Child, Preschool; D004072:Digitonin; D005260:Female; D005347:Fibroblasts; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D006801:Humans; D007223:Infant; D007425:Intracellular Membranes / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000097:blood; D008928:Mitochondria / Q000378:metabolism*; D009952:Ornithine / Q000097:blood / Q000378:metabolism*
D000596:Amino Acids; D009952:Ornithine; D007770:L-Lactate Dehydrogenase; D005969:Glutamate Dehydrogenase; D004072:Digitonin