AMINOACIDURIA

From Big Medical Encyclopedia

AMINOACIDURIA (amines + lat. acidus — acid and Greek uron — urine; synonym hyper aminoaciduria) — the increased removal with urine of one or several amino acids or an intermediate product of the amino-acid exchange which normal is not contained in urine. The aminoaciduria concerns to group of biochemical deviations which can be established long before emergence of clinical symptoms of a disease. In one cases of Aminoatsiduriya is the major laboratory indicator for diagnosis, in others — only supplements the main biochemical syndrome of a disease. Aminoatsiduriya's development

is the cornerstone of disturbance of intermediary exchange or transport of amino acids at the level of cellular membranes of renal tubules. Proceeding from a pathogeny, Aminoatsiduriya is subdivided into several groups.

Prerenal, or reloading, Aminoatsiduriya arises at increase in level of amino acids in a blood plasma owing to defect in the enzymes participating in exchange of amino acids or as the secondary phenomenon at the diseases damaging the deaminizing function of a liver. Prerenal Aminoatsiduriya's example is the phenyl-pyruvic oligophrenia (see. Oligophrenias ), histidinemia (see), a disease of «maple syrup» (see. Dekarboksilaznaya insufficiency ), glitsinemiya (see), homocystinuria (see), arginineamber aciduria, β-hydroxy-isobutyric aciduria and other diseases.

The renal aminoaciduria appears at insufficiency of transport enzymatic systems. Healthy people have 98% and more amino acids reabsorbirutsya by renal tubules. In this regard renal clarification of the majority of amino acids makes 2 — 6 ml/min. / 1,73 m 2 [Kusvort, Dent (D. Page of Cusworth, E. S. of Dent), 1960].

The delay of maturing of amino-acid transport systems of kidneys at newborn children leads to emergence physiological nonspecific And. Daily excretion of amino nitrogen reaches 10 mg/kg at norm no more than 2 mg/kg for children of advanced age and adults. Huge impact on transport of amino acids is exerted by ions of sodium. The reabsorption of amino acids considerably accelerates upon transition of sodium to extracellular space. A mediator in transport of amino acids is vitamin B 6 in the form of pirpdoksal-5-phosphate. ATP as the accumulator of the energy necessary for active process of a reabsorption and phosphorylation of vitamin B has a direct bearing on transport of amino acids 6 . Transport of amino acids can be suppressed at high concentration in a gleam of a renal tubule of glucose, fructose, a galactose and their metabolites.

It is established that there are at least four groups of enzymatic systems for active transport of amino acids in intestines and renal tubules [Milne (M. of D. Milne), 1964; Hollerman, Kalkanyo (S. E. Hollerman, P. L. Calcagno), 1968]; in each of them existence of additional transport systems for separate amino acids is possible. The first transport system provides a reabsorption of neutral monoamino monocarboxylic amino acids (alanine, series, threonine, valine, a leucine, an isoleucine, phenylalanine, tyrosine, tryptophane, asparagine, a glutamine, a histidine, cysteine, methionine, citrulline).

An example of disturbance in the first group of enzymatic system of amino acids is Hartnupa disease (see). Dibasic amino acids (ornithine, arginine, a lysine) and cystine have also organonespetsifichesky transport system (the second group of enzymatic system). Hereditary defects in this system are shown very often in a look cystinurias (see). Transport of dicarboxylic (acid) amino acids (asparaginic and glutamnnovy) is carried out by the third group of enzymatic system. Hereditary diseases at defeat of this system are unknown. The fourth, iminoglycine, enzymatic system exists for proline, oxyproline and glycine. A prototype renal Ampere-second disturbance of a reabsorption of amino acids and glycine can serve a family renal prolinuriya and a glycinuria.

The mixed aminoaciduria of reloading and renal genesis is characterized by the increased removal not only that amino acid, concentration a cut in plasma is high, but also other acids having the general transport system owing to an overload of the last. Examples mixed And. the prolinemiya and a tsitrullinuriya are. At a tsitrullinuriya, except the increased removal citrulline (see), increase in excretion with urine of alanine, asparagine, a histidine, serine and glycine which concentration in a blood plasma is normal is observed. Prolinempya and a prolinuriya cause secondary renal And. at the expense of two amino acids, other, close on transport system — oxyproline and glycine.

Secondary renal aminoacidurias arise owing to toxic action on a proximal part of nephron of various exogenous N of endogenous substances: lead, oxalic and apple acids, lysol, phosphorus, uranium, cadmium, copper at Wilson-Konovalov's disease (see. Hepatocerebral dystrophy ), Bens-Jones's squirrel at a myeloma. Similar changes are noted at a vitamin deficiency, rickets, a nephrotic syndrome, Tony — Debra — Fankoni a syndrome (see), Lowe syndrome (see), cystinosis (see), galactosemia (see), fruktozemiya (see), glycogenosis (see) and other diseases. And. at the listed states it is not specific and therefore is of secondary importance for diagnosis of a basic disease, but it can serve as criterion for evaluation of treatment — permanent disappearance And. demonstrates progress of therapy. Aminoatsiduriya's diagnosis along with definition of the general amino nitrogen of urine requires carrying out a hromatografichesky research of amino acids of blood and urine with determination of their clearance (see. Clearance test ). For early diagnosis various rapid tests for amino acids and their metabolites [Berry (N. K. of Berry), can be used 1960; Nayen and W. L. Nyhan, 1967].



Bibliography: Lebedev V. P., etc. Primary and secondary hyper aminoacidurias at children, Vopr. okhr. mat. also it is put., t. 15, No. 11, page 64, 1970, bibliogr.; Netakhata Zh. N. and Lyapun S. N. Amino-acid exchange and pathology of children's age, Pediatrics, No. 12, page 63, 1970, bibliogr.; Ninov of I. N. Aminoatsiduriya at children, in book: New probl. in pediatrics, under the editorship of L. Bakalova. the lane with bolg., century 5, page 131, Sofia, 1968, bibliogr.; Amino acid metabolism and genetic variation, ed. by W. L. Nyhan, N. Y., 1967, bibliogr.; Woolf L. J. Renal tubular dysfunction, Springfield, 1966.


V. P. Lebedev.

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