Variant of canine erythrocytes with high potassium content and lack of glutathione accumulation.

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.