Summary
Although the cation composition of mature erythrocytes in clinically normal dogs comprises low K concentration and high Na concentration because of lack of a Na/K pump, a dog was found that had erythrocytes with high K and reduced glutathione (gsh) concentrations attributable to the existence of a Na/K pump (hk/hg cells). However, 2 dogs were subsequently found that had erythrocytes with high K concentration and increased Na/K pump activity, but without high gsh accumulation (hk/lg cells). In those hk/lg cells, Na-dependent glutamate and aspartate influxes were about a sixth of the values in hk/hg cells, despite a steep Na gradient, and cellular glutamate concentration was not accumulated in hk/lg cells as it was in hk/hg cells. In the latter cells, glutamate and aspartate accumulated because of high activity of Na-dependent amino acid influxes. Therefore, low concentration of glutamate may be the reason for the low gsh concentration in hk/lg cells. In such cells, however, aspartate and glutamine were accumulated similarly as they were in hk/hg cells. The hk/lg cells also had a defect in amino acid metabolism. This defect was different from that in hk/hg cells. Thus, hk/lg cells might be a new model for study of defects in amino acid transport and amino acid metabolism.
