Urine glutamine

Excretion into urine of ammonia produced by renal mbu-lar cells facilitates cation conservation and regulation of acid-base balance. Ammonia production from intracellular renal amino acids, especially glutamine, increases in metabolic acidosis and decreases in metabolic alkalosis. 

Hyperammonemia Type 2. A deficiency of ornithine transcarbamoylase (reaction 2, Figure 29-9) produces this X chromosome-linked deficiency. The mothers also exhibit hyperammonemia and an aversion to high-protein foods. Levels of glutamine are elevated in blood, cerebrospinal fluid, and urine, probably due to enhanced glutamine synthesis in response to elevated levels of tissue ammonia. 

One trick is the administration of benzoate or phenylac-etate. These acids react with glycine or glutamine, respectively, to produce complexes (conjugates) which are excreted in the urine (Figure 10.10). This decreases the plasma level of either of these non-essential amino acids... 

Tin metabolic acidosis (p. 652) there is an increase in glutamine processing by the kidneys. Not all the excess NH4 thus produced is released into the bloodstream or converted to urea some is excreted directly into the urine. In the kidney, the NH% forms salts with metabolic acids, facilitating their removal in the urine. Bicarbonate produced by the decarboxylation of a-lcetoglutarate in the citric acid cycle can also serve as a buffer in blood plasma. Taken together, these effects of glutamine metabolism in the kidney tend to counteract acidosis. ... 

FIGURE 18-14 Treatment for deficiencies in urea cycle enzymes. The aromatic acids benzoate and phenylbutyrate, administered in the diet, are metabolized and combine with glycine and glutamine, respectively. The products are excreted in the urine. Subsequent synthesis of glycine and glutamine to replenish the pool of these intermediates removes ammonia from the bloodstream. 

Column chromatography yields quantitative results even for constituents present in only small amounts (with the exception of tryptophan, methionine, and glutamine, in which cases the recovery is not complete see below, (b) Dowex 50-X4 columns). It lends itself also to extraction on a preparative scale for further analysis of a particular constituent it does not require previous desalting of urine. The major inconvenience of ion exchange column chromatography for routine analyses is that the technique is elaborate and time consuming, and requires experienced personnel and expensive equipment. Recent developments, however, have allowed for considerable reduction in time consumption, and the latest completely automatic devices open the way to serial analyses. 

The chromatograms always indicate the excretion of considerable amounts of glutamine (and glutamic acid), but it is not possible to arrive at accurate values for glutamine (see text). The values for this amide are therefore to be considered as very approximate, indicating merely that it is found in urine in considerable amounts. 

An adolescent went into delirium after eating a high-protein meal. He had an extremely high blood ammonia level and excreted orotic acid and uracil in the urine. His blood also contained increased glutamine and lysine levels. Despite heroic symptomatic treatment, the patient expired after 2 weeks. His liver tissue showed normal urea cycle enzyme levels, except that for ornithine transcar-bamylase (OTC), whose activity was only 10% that of normal liver. The Km of OTC was normal. Liver carabmylphosphate levels were about 10 times normal. Theoretical computer simulations indicated that urea can be produced at normal rates when liver OTC levels are higher than 0.3% of normal. 

All enteral feeds were stopped. The baby was given intravenous glucose, L-arginine, sodium benzoate, and sodium phenylacetate. Hemodialysis was initiated. At this time, there were no spontaneous respirations, there was no response to painful stimuli, and brainstem reflexes were absent. The plasma amino acid results revealed a glutamine level of 1500 pmol/L (normal 254-823), and citrulline was undetectable (normal 10-34 pmol/L). Quantitative carnitine, plasma acylcarnitine, and urine organic acid profiles were normal. The urine orotic acid concen-... 

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