Urinary amino acid nitrogen

An increase in one or more amino acids in urine is called amino acid urine. With the understanding of genetic diseases, the examination of amino acid urine has been valued. Due to the high renal threshold of plasma amino acids, only small amounts of amino acids can occur in normal urine. Even if it is filtered out by the glomerulus, it is easily reabsorbed by the renal tubules. Amino acids in urine are divided into two types: free and bound. The free type is about 1.1g / 24h, and the combined type is about 2g / 24h. Binding type is the product of amino acid conversion in the body, such as glycine and benzoic acid to form hippuric acid; N-2 acylglutamic acid and benzoic acid combine to form phenylacetylglutamic acid. The content of amino acids in normal urine is significantly different from that in plasma. The amino acids in urine are mainly glycine, histidine, lysine, serine and aminoethanesulfonic acid. There is a large difference in excretion in the age group. The excretion of some amino acids in children is higher than that in adults, which may be due to the immature renal tubular development and reduced reabsorption. But & beta; -aminoisobutyric acid, glycine, aspartic acid, etc. were significantly higher in adults. In addition to being related to age, urine amino acids are also significantly different due to diet, genetic and physiological changes, such as histidine and threonine in urine during pregnancy can be significantly increased. Examination of amino acids and their metabolites in urine can be used as a screening test for amino acid abnormalities in hereditary diseases. Increased amino acid concentration in the blood can overflow in the urine, seen in some congenital diseases. For example, due to kidney poison or drug damage, renal tubular reabsorption disorder, lower renal threshold, and renal amino acid urine, the amino acid concentration in the patient's blood is not high. Amino acid nitrogen in serum accounts for about 25% of non-protein nitrogen.