ORGANIC SOLUTE PERMEABILITY IN ERYTHROCYTES OF THE LITTLE SKATE, RAJA-ERINACEA

Neutral, organic molecules with seven or less major atoms permeate erythrocytes of the little skate (Raja erinacea). Hypotonicity (80%) increased permeation up to 10-fold. Under both isotonic and hypotonic conditions solute influx occurred with the same size limitation, indicating that the number of permeation sites, but not their size, increases with hypotonicity. The maximum average diameter of these neutral molecules that penetrate the cell membrane is about 5.6 to 6.2 angstrom. This is similar to that found previously for amino acid permeation, but unlike amino acids, the entry of most of the organic, neutral molecules into skate erythrocytes is not affected by Band 3 inhibitors. These results suggest that the neutral molecules tested may enter the erythrocytes via the same channel as amino acids, but do not interact with the sites blocked by Band 3 inhibitors, or through a separate channel of similar size which is also volume activated. (C) 1993 Wiley-Liss, Inc.