Intestinal Absorption and Renal Extraction of Cystine and Cysteine in Cystinuria

A NUMBER of in vivo1 2 3 and in vitro4 5 6 studies in cystinuric patients have shown the presence of defects in renal and intestinal transport of the dibasic amino acids lysine, arginine and ornithine. However, studies of intestinal absorption of cystine and the mechanisms by which this amino acid appears in the urine in such marked excess in cystinuria have been far more difficult to interpret. An intestinal-transport defect for cystine has been demonstrated in vitro,5 , 6 and Milne and his co-workers3 have called attention to previous in vivo feeding studies suggesting defective absorption of this amino acid. Several studies7 8 9 have reported that . . .