Cystinuria: Defective Intestinal Transport of Dibasic Amino Acids and Cystine*

Abstract

The clinical manifestations of cystinuria are lo- calized to the urinary tract and result from the formation of cystine calculi. The findings of in- creased excretion of cystine, lysine, arginine, and ornithine in the urine at a time when the plasma levels of these amino acids were normal or low suggested to Dent and Rose (2) that a renal tu- 1)ular reabsorptive site, shared by the involved amino acids, was defective. Investigations from our laboratory (3), using slices of human kidney, failed to confirm the hypothesis of Dent and Rose. Cystine did not compete with the dibasic amino acids in vitro, and although the transport of ly- sine and arginine was defective in cystinuria, cys- tine transport was unimpaired.