The extent and time course of the impairments occurring in whole blood and erythrocyte cells stored under blood bank conditions were studied by monitoring the reduction of MAL-6 spin label added to the media containing whole blood or erythrocyte cells using electron spin resonance (ESR) technique. Impairments forming in the erythrocyte cells incubated for various times at 37degreesC were also studied. Erythrocyte cells were found to undergo changes during the storage or incubation, leading to fast decay of MAL-6 spin labels signal height. The extent of the changes depends on storage or incubation time. However, the reduction in incubated or artificially aged erythrocyte (AAE) cells was faster than the reduction in whole blood (WB) and aged erythrocyte (AE) cells stored under blood bank conditions. Two exponential curves attributed to the liquid and cellular parts of a given samples were found to be described best in the reduction of MAL-6 spin label in WB, AE and AAE. (C) 2003 Elsevier B.V. All rights reserved.