Organic acids in blood and urine from normal healthy adults and children

Abstract

The organic acid profile in urine from normal subjects has been studied by several groups using a variety of extraction and chromatographic techniques and normal subjects defined and selected using different criteria. Prior to the application of GC and MS methods to the study of organic acids in urine, a considerable amount of information was obtained on the occurrence of these compounds in physiological fluids (Nordmann and Nordmann, 1961). Citric acid was among the first organic acids to be reported in urine (Amberg and McClure, 1917), and later application of paper chromatography and silicic acid chromatography revealed the presence of most of the other acids of the tricarboxylic acid cycle, including cis-aconitic, isocitric, 2-oxoglutaric, succinic, fumaric and malic acids at varying concentrations. Most of these acids were also reported to occur in blood and detected using specific enzymic and other analytical techniques (see Nordmann and Nordmann, 1961). The acids of the tricarboxylic acid cycle are partially affected by diet and particularly by alterations in the acid-base balance. For example, citrate excretion may be affected by alterations in carbohydrate (starch) intake, and increases (as does 2oxoglutarate excretion) in metabolic alkalosis, being reduced in acidosis (Nordmann and Nordmann, 1961; Gamble et al., 1961). Pyruvic acid is the dominant oxo acid of blood, whereas 2-oxoglutarate predominates in urine. Lactic acid also occurs in predominating amounts in blood, whereas it does not occur in urine to any extent in normal rested individuals.