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Transport of dibasic amino acids, cystine, and tryptophan by cultured human fibroblasts: absence of a defect in cystinuria and Hartnup disease

Ulrich Groth and Leon E. Rosenberg

Division of Medical Genetics, Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06510Division of Medical Genetics, Department of Medicine, Yale University School of Medicine, New Haven, Connecticut 06510

Published August 1972

Transport of lysine, arginine, cystine, and tryptophan was studied in cultured skin fibroblasts from normal controls and from patients with cystinuria and Hartnup disease. Each of these amino acids was accumulated against concentration gradients by energy-dependent, saturable mechanisms. Lysine and arginine were each transported by two distinct processes which they shared with each other and with ornithine. In contrast, cystine was taken up by a different transport system with no demonstrable affinity for the dibasic amino acids. The time course and Michaelis-Menten kinetics of lysine and cystine uptake by cells from three cystinuric patients differed in no way from those found in control cells. Similarly, the characteristics of tryptophan uptake by cells from a child with Hartnup disease were identical to those noted in control cells. These findings indicate that the specific transport defects observed in gut and kidney in cystinuria and Hartnup disease are not expressed in cultured human fibroblasts, thus providing additional evidence of the important role that cellular differentiation plays in the regulation of expression of the human genome.

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