Na-dependent glutamate transport in high K and high glutathione (HK/HG) and high K and low glutathione (HK/LG) dog red blood cells.
Na-dependent glutamate (Glu) influxes in the red blood cells of normal low K (LK), high K and high glutathione (HK/HG), and high K and low glutathione (HK/LG) dogs were compared. The ranges of the influxes in LK, HK/HG and HK/LG cells were 1.0-63, 62-174 and 1.3-26 mumol/1 cells per h, respectively. Some LK and HK/LG dogs had red blood cells with extremely low Glu influxes. In cells with extremely low Glu influxes, however, there were clear Na-dependent Glu influxes. In LK, HK/HG and HK/LG cells, the Km of Na-dependent Glu influx with respect to the medium Glu concentration were 17, 20 and 19 mM, respectively, and the half-maximal activation (K1/2) with respect to medium Na concentration was 39, 40 and 42 microM, respectively. By the addition of harmaline, a hallucinogenic alkaloid, the Vmax in LK cells was not affected and the Km was increased, while the Vmax was decreased and the Km increased in HK/HG and HK/LG cells. The Ki value with harmaline by means of Dixon plot in LK cells was 5.2 mM, against 1.8 and 1.9 mM in HK/HG and HK/LG cells, respectively. These results suggest that the difference in the Na-dependent Glu influxes between 2 HK groups was due to the varying quantity, not the quality, of the transporter.
Fujise
H
H
Department of Pathology, School of Veterinary Medicine, Azabu University, Kanagawa, Japan.
Hamada
Y
Y
Mori
M
M
Ochiai
H
H
D018528:ATP-Binding Cassette Transporters / Q000097:blood; D027322:Amino Acid Transport System X-AG; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004285:Dogs; D004912:Erythrocytes / Q000378:metabolism*; D018698:Glutamic Acid / Q000097:blood*; D005978:Glutathione; D006246:Harmaline / Q000494:pharmacology; D007700:Kinetics; D011188:Potassium; D012964:Sodium / Q000502:physiology
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D018698:Glutamic Acid; D012964:Sodium; D006246:Harmaline; D005978:Glutathione; D011188:Potassium