Transport of neutral amino acids across the human red blood cell membrane.

1. Genetic markers are important in the search for genetically transmitted entities related to clinical nosology with implications for etiology, prophylaxis and treatment. 2. Rafaelsen (1976) has proposed a membrane transport model of affective disorders focusing on phase-independent transport deficiencies. 3. The transport of some neutral amino acids (L-leucine, L-phenylalanine and L-tryptophan) has been studied in the human erythrocyte at 25 degrees C. 4. A group- and a tryptophan-specific amino acid transport system have been described. 5. The relation to the model of Rafaelsen is discussed. 6. It is concluded that clinical studies should be undertaken to test whether these biological characteristics consistent with a specific theory are biological-etiological markers.