Transport of Neutral and Dibasic Amino Acids by Human Leukocytes: Absence of Defect in Cystinuria*

Abstract
Leukocyte suspensions, prepared from peripheral blood of normal volunteers by dextran sedimentation and hypotonic erythrocyte lysis, were noted to transport neutral and dibasic amino acids against chemical gradients in-vitro by processes that are saturable and are dependent on energy generated by anaerobic glycolysis. Studies with ouabain and with reduced medium Na concentration indicated that the transport of alanine and cystine but not of lysine and arginine depends on a functioning membrane cation transport mechanism or critical transmembrance concentrations of Na and K, or on both. Lysine, arginine, and ornithine shared a single transport system not utilized by cystine. Kinetic analysis suggested that this common transport mechanism differs from that in gut and kidney. No defect in the transport of the dibasic amino acids or cystine was found in leukocytes from cystinuric subjects. The complexities apparent in studies of dibasic amino acid transport in several human tissues and their possible genetic control mechanisms are discussed.