STUDY DESIGN AND METHODS: Within 24 hours of collection, blood concentrates were split in 250 ml and irradiated with 25 Gy. At days 1, 7, 14 and 28, fractions were removed and centrifuged. Plasma Na⁺, K⁺, Ca²⁺, LDH activity, and pH were measured. Na⁺,K⁺-ATPase and Ca²⁺-ATPase from ghost membranes were assessed. Inside-out vesicles from ghosts were used to evaluate [⁴⁵Ca]Ca²⁺-uptake and release.

RESULTS: The plasma pH, LDH activity, and Ca²⁺ concentrations were not affected by irradiation. The plasma K⁺ of irradiated samples doubled within the first day, and increased thereafter until day 28. The plasma Na⁺ decreased, this effect was more pronounced in irradiated samples. The Na⁺,K⁺-ATPase activity was not immediately affected by irradiation, but was inhibited by 40% by day 14. The Ca²⁺-ATPase was not affected by irradiation. The rate and the end level of [⁴⁵Ca]Ca²⁺ uptake were reduced, and the passive efflux of Ca²⁺ was increased.
CONCLUSION: Irradiation of blood concentrates did clearly not alter the plasma pH nor disrupted erythrocyte membranes, but increased the permeability of the membrane and decreased Na⁺,K⁺-ATPase activity. Although the Ca²⁺-ATPase activity was not affected, the sum of these effects would lead to altered ion homeostasis and cell function.