An evaluation of erythrocytes as plasma glutamate scavengers for enhanced brain-to-blood glutamate efflux.

Several acute brain pathological conditions are characterized by the presence of excess glutamate in brain interstitial fluid. We have previously shown that decreasing blood glutamate levels increases the driving force for an enhanced brain-to-blood efflux of glutamate. The present study investigated the glutamate pumping ability of glutamate-depleted erythrocytes both in vitro and in vivo to determine whether the latter could potentially be used in a blood exchange procedure for neuroprotection. We have observed that glutamate is taken up in red blood cells only via a passive diffusive process with a diffusion constant of 0.144/h. When glutamate-depleted blood cells resuspended in 6% hetastarch were injected into recipient rats, using a blood exchange protocol, a decrease of blood glutamate was observed but attributed to plasma dilution. These observations are discussed in light of a novel neuroprotective strategy based on blood glutamate scavenging.