Urine glyoxylic acid

Ethyl benzene distributes to the adipose tissues. It is metabolized to mandelic acid (64%) and phenyl-glyoxylic acid (25%). The percentage of metabolites may vary according to the route of exposure with mandelic acid formation being favored with inhalation. The primary route of excretion is via the urine. Experimental evidence indicates that the percutaneous absorption rate of ethyl benzene is 37 pgcm... 

When introduced via the oral or inhalation routes, tetrachloroethane is metabolized primarily to tri-chloroethanol, trichloroacetic acids that are subsequently broken down to glyoxylic acid, oxalic acid and carbon dioxide and are excreted chiefly as metabolites in the breath and urine. A small amount is expired in the breath as carbon dioxide and as the parent compound. 

Glyoxylic Acid. Trace amounts of glyoxylic add have been detected by some workers in normal blood and/or urine (B18, H19, Kl, VI, Z2), whereas others did not find it on normal chromatograms of... 

A carboxylic acid, normally excreted in the urine in small amounts. It is a constituent of many urinary tract stones. High levels of oxalic acid are excreted in the urine in the rare inborn error of metabolism, primary hyperoxaluria. In this disorder renal stones composed of oxalate are formed and death results from progressive renal failure. The increase in the urinary excretion of oxalic acid appears to be derived from glycine as a result of deficient glyoxylic acid-glycine transamination. 

When styrene is inhaled, about two-thirds are resorbed it can also be absorbed through the skin [197]. It accumulates in all organs, but principally in the liver, kidneys and blood and is also found in faeces [197]. It is oxidized at the double bond and decomposed to mandelic acid and phenyl glyoxylic acid which are easily identifiable in the urine [195]. Benzoic acid has also been detected in rabbits [197]. As with the xylenes, excretion takes about three days [197]. If guinea-pigs are exposed to only about 1 ppm styrene (0.005 mg/1), however, no mandelic acid is detected in the urine - only at higher concentrations [197]. 

More recently, Henning and Ammon (H19) described 10 aliphatic keto and aldehydic adds in normal urine. In addition to a-ketoglutaric, oxalacetic, pyruvic, glyoxylic, and a-ketoisocaproic acids, they found hydroxypyruvic, a-keto-y-methylthiobutyric, a-keto-fi-hydroxybutyric, a-keto-P-methylvaleric and a-keto-n-butyric acids, that is to say, the keto acids corresponding, respectively, to serine, methionine, threonine, isoleucine, and a-amino-n-butyric acid. They conclude that one finds in normal human urine the keto acids corresponding to all the amino adds normally present in urine, with the exception of those correspond-... 

The oxidation of glyoxylate to oxalate is catalyzed by xanthine dehydrogenase (30). The reaction also takes place in pigeon liver homogenate which contains no xanthine dehydrogenase. Oxalic acid cannot be an important intermediate in the catabolism of glycine because of its inertness to further oxidation. Apparently any oxalate formed in the body is eliminated by excretion in the urine. 

The resultant purine bases, guanine and hypo-xanthine (from AMP and dAMP), may be either salvaged (Section 16.6) or converted to xanthine. The oxidation of xanthine by xanthine oxidase yields urate (uric acid) which is excreted in the urine of man and primates. Other organisms are capable of the synthesis of various enzymes which permit the continuation of the pathway to various end products, e.g. allantoin in mammals, urea and glyoxylate in most fishes (not teleost fishes) and amphibians, and ammonia and COj in crustaceans. 

Fig. 16.4 Chromatogram of organic acids extracted using DEAE-Saphadex from the urine of a patient with primary hyperoxaluria type I, separated as their ethoxime and trimethylsilyl derivatives on 10 per cent OV-101 on HP Chromosorb W (80-KX) mesh) using temperature programming from 110°C to 285°C at 4°C min with a 5 min initial isothermal delay. Peak identifications are 1, glyoxylate 2, glycollate 3, oxalate 4, sulphate 5, phosphate 6, tetronates 7, citrate 8, undecanedioate (internalstandard) 9, Az-tetracosane (standard) 10, -hexaxosane (standard).

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