Kinetics of extracellular potassium concentration in irradiated red blood cells.

Abstract

Irradiation of cellular blood components prevents onset of transfusion-associated graft-versus-host disease. The present study was designed to monitor the post-irradiation changes of the extracellular potassium concentration in red blood cells (RBC) stored in SAG-M (saline adenine glucose-mannitol), in order to estimate the right time for their prophylactic irradiation and the right span of post-irradiation storage. Ten units each of fresh, 10 days and more than 20 days stored SAG-M RBCs were divided into 2 equal portions each. One portion was gamma-irradiated with 30 Gy (137Cs-source). Another 10 fresh RBC units were separated, and portions were irradiated with 15, 30, 60 or 120 Gy. The determination of potassium was performed simultaneously in corresponding irradiated and non-irradiated portions; immediately after irradiation, after 1 and 5 days, and every 10 days of additional storage (up to 30 days). All measurements were performed in the cell-free supernatant, using flame emission photometry. The extracellular potassium concentration increased permanently with the duration of storage both in non-irradiated and irradiated specimens. At the end of the period of storage this increase in the irradiated portions was approximately 2 times the potassium concentration of the non-irradiated portions (60 mmol/l vs. 38 mmol/l, p < 0.001). Thereby no significant differences of the potassium efflux rates were estimated at the end of the period of storage between fresh RBCs irradiated and stored RBCs irradiated. The mean 5 days post-irradiation potassium release from fresh RBC units was similar to that in 25-30 days stored non-irradiated portions (34.3 mmol/l vs. 38 mmol/l). The extracellular potassium increase was irradiation dose-dependent (r = 0.89, p < 0.001). SAG-M RBCs can be irradiated with 30 Gy immediately post-harvest and subsequently stored for a couple of days prior to transfusion without producing critically high extracellular potassium concentrations.