Studies on the Transport Mechanism of Aminoacids in the Renal Tubules : Part I Studies on the Mechanism of Aminoaciduria from the Analytical Standpoint of Titration Curve

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1) It has been revealed that glycine, threonine, and histidine have their own Tm. Experimentally an analysis is made of the titration curve of the aminoacids after loading of amino-acid-mixture and 1-histidine loading to patients with renal diseases and to normal subjects. A reabsorption ratio is decreased in renal disease cases in a range up to the load area of Tm. 2) An increase of loaded amounts of amino-acids resulted in a gentle continuous slope but never "shoulder" on the titration curve. This "shoulder" phenomenon observed on the glucose titration curve is considered to be due to the presence of the nephron population. It is therefore, not referable to aminoacids. Assuming that the transfer reaction proceeds as follows : A+B<ruluhar>AB<roarra6gt;B+A where A is transferred material B is carrier AB is complex, then, equation, K(x-y)(c-y)=y, can be introduced where x corresponds to loaded amount, c the number of carriers, y a transferred amount and K equilibrium constant. If K is of a finite value in the reaction of the first degree, one can not expect "shoulder" phenomenon in the titration curve. 3) A deformed titration curve in cases of diseased kidney suggests the presence of a decrease of c (carrier) and also of an apparent decrease of K. Although the decrease of K can be expected from transfer enzyme abnormalities in cases of congenital aminoaciduria, it is hard to expect its occurrence in non-specific renal lesions. 4) On the basis of the present data, a new classification is proposed of aminoaciduria. Renal aminoaciduria in a narrow sence is due to abnormalities of the transfer reaction system, manifested by a decrease of c (carrier) and K (equilibrium constant), characterized by a decrease of Tm and reabsorption ratio. In aminoaciduria of hepatic coma cases which has been , formerly grouped in overflow type, abnormalities are pointed out in the transfer reaction system as well as increase of plasma aminoacids. A new term of "overload amino aciduria" is proposed for cases with a filtered load below Tm. Phenylketonuria is considered to be a typical overload aminoaciduria.
社団法人日本循環器学会の論文
1967-03-20

Studies on the Transport Mechanism of Aminoacids in the Renal Tubules : Part I Studies on the Mechanism of Aminoaciduria from the Analytical Standpoint of Titration Curve

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