Abstract
Excretion of succinic acid in large amounts has been demonstrated by the use of gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) in urine of a 9 year-old girl of Japanese extraction with low normal intellegence, exophthalmos, congenital contraction of elbows and dislocation of hip. A twenty four hour urine specimen was diluted to 1,000 ml with distilled water and prepared for gas chromatography and GC-MS in the following fashion. Firstly, 8 ml of urine was half-saturated with an equal volume of saturated NaCl solution and acidified with 6 N-HCl, then extracted with 8 ml of ethyl acetate and 8 ml of ethyl ether, twice respectively. The extracts were combined and dehydrated with magnesium sulfate prior to evaporation. Since the extraction procedure is, however, not necessarily of sufficient efficacy as far as fatty acids other than aromatic fatty acids are concerned, two ion-exchange chromatographic methods were applied as well. A DEAE-Sephadex column, 1.3 cm i. d. and 9 cm in height, was equilibrated with 0.5 M pyridine-acetate solution and 10 ml of urine was loaded. The adhering fatty acids were eluted with 150 ml of 1.4 M pyridine-acetate solution. The other chromatographic column contained 3.0 g of Dowex 2-×8 resin, 200-400 mesh, in formate form, to which 5 ml of urine, deproteinized with 30% perchloric acid, was transferred. Elution was performed with 20 ml of 12 N-formic acid. The eluates were then lyophilized and the residues were redissolved with methanol, dryed out in nitrogen stream, then trimethylsilylated for GC and GC-MS. The gas chromatograph used was equipped with dual columns, 2 m in length, packed with Gas chrom Q coated with 5% OV-1, and with hydrogen flame ionization detectors. The column temperature was programmed by 3°/ min from 80° up to 250°.
A characteristically high peak detected by GC in urine preparation from the patient in comparison with those from control subjects. Mass spectrum of the compound showed parent ion of m/e 262 corresponding to that of succinic acid, of which two carboxyl groups were trimethylsilylated. Elemental analysis based on either the high resolution mass spectrometry or the medium resolutional electrostatic field mass spectrometry were also compatible with succinic acid.
Physiological significance of massive excretion of succinic acid in urine of this patient remains obscure, though lesions in TCA cycle, especially in succinyl CoA synthetase and/or succinate dehydrogenase, resulting in reduction in energy production and presumably affecting GABA shunt secondarily, appear most persuasive.
