CHARACTERISTICS OF ACIDIC AMINO ACID TRANSPORT IN MAMMALIAN KIDNEY

Abstract

A series of clearance experiments on dogs were carried out which were designed to confirm and characterize the renal tubular reabsorption of glutamic and aspartic acids. Tubular reabsorption was measured and found to reach a maximum of about 100 μmole/minute for L-glutamic and L-aspartic acids and a slightly lower level for D-aspartic. Competitive studies using substituted amino acids were performed and three patterns of inhibition of amino acid reabsorption observed. Acidic amino acids inhibited the reabsorption of each other, while neutral amino acids (and an acidic amino acid substituted so as to have a neutral side chain) inhibited the reabsorption of a wide range of other amino acids. Compounds with the amino group or either carboxyl group substituted or absent, but not resembling neutral amino acids, were not inhibitory. There appears to be a specialized mechanism for acidic amino acid transport which probably requires all three functional groups but which may be interfered with by a compound with alpha carboxyl and amino groups and a neutral side chain.