COMPARISON OF GLUTAMATE METABOLISM IN LOW K (LK), HIGH K AND HIGH GLUTATHIONE (HK HG) AND HIGH K AND LOW GLUTATHIONE (HK/LG) DOG RED-BLOOD-CELLS/

The reasons for the high accumulation of glutamate (Glu), aspartate (A sp) and glutamine (Gln) in high K and high glutathione (HK/HG) dog red blood cells (DRBCs) have been explained as due to enhanced Glu/Asp in fluxes. However, in our study, Glu/Asp influxes in high K and low glut athione (HK/LG) DRBCs were low, whereas their cellular Asp and Gin con tents were high. In low K (LK) DRBCs, there were also other variant ce lls with high Asp accumulation, but extremely low Glu/Asp influxes. So , the high amino acid accumulation in DRBCs of these new variants migh t not be due to Glu/Asp influxes. To examine the high accumulation of these amino acids in these variant DRBCs, first, LK and HK/LG DRBCs we re classified into two subgroups with their Na-dependent Glu/Asp influ xes; one had clear Na-dependent Glu/Asp transport (GAT(+)), and the ot her failed to have any transport (GAT(-)). The influxes of both Glu an d Asp in HK/HG DRBCs were the highest, and the order was HK/HG> LK/GAT (+)> HK/LG/GAT(+)> >LK/GAT(-) = HK/LG/GAT(-). LK/GAT(+) cells represen ted normal DRBCs. Glu/Asp influxes were only trace in both LK/GAT(-) a nd HK/LG/GAT(-) cells, but Glu and Asp concentration was high in HK/LG /GAT- cells whereas Asp concentration was high in LK/GAT(-) cells. In HK/HG cells, the conversion of Glu into Gin in whole cells was several fold higher than in the other cell groups due to the differing amount of the substrate of glutamine synthetase, Glu, but glutamine syntheta se activity itself was not different among these cell groups. Furtherm ore, glutamine synthetase and glutaminase activities were not differen t among the cell groups. Therefore, these enzymes were not involved in the high amino acid accumulation.