KINETICS OF EXTRACELLULAR POTASSIUM CONCENTRATION IN IRRADIATED RED-BLOOD-CELLS

Background: Irradiation of cellular blood components prevents onset of transfusion-associated graft-versus-host disease. The present study w as designed to monitor the post-irradiation changes of the extracellul ar potassium concentration in red blood cells (RBC) stored in SAG-M (s aline adenine glucose-mannitol), in order to estimate the right time f or their prophylactic irradiation and the right span of post-irradiati on storage. Materials and Methods: Ten units each of fresh, 10 days an d more than 20 days stored SAG-M RBCs were divided into 2 equal portio ns each. One portion was gamma-irradiated with 30 Gy (Cs-137-source). Another 10 fresh RBC units were separated, and portions were irradiate d with 15, 30, 60 or 120 Gy, The determination of potassium was perfor med simultaneously in corresponding irradiated and non-irradiated port ions: immediately after irradiation, after 1 and 5 days, and every 10 days of additional storage (up to 30 days). All measurements were perf ormed in the cell-free supernatant, using flame emission photometry. R esults: The extracellular potassium concentration increased permanentl y with the duration of storage both in non-irradiated and irradiated s pecimens. At the end of the period of storage this increase in the irr adiated 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 irrad iated and stored RBCs irradiated. The mean 5 days post-irradiation pot assium 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 extrac ellular potassium increase was irradiation dose-dependent (r = 0.89, p < 0.001). Conclusions: SAG-M RBCs can be irradiated with 30 Gy immedi ately post-harvest and subsequently stored for a couple of days prior to transfusion without producing critically high extracellular potassi um concentrations.