Microwave bioeffects in the erythrocyte are temperature and pO2 dependent: cation permeability and protein shedding occur at the membrane phase transition.

Microwave exposure (2450 MHz, 60 mW/g, CW) of rabbit erythrocytes increases Na passive transport only at membrane phase transition temperatures (Tc) of 17-19 degrees C. This permeability effect is enhanced for relative hypoxia which is characteristic of intracellular oxygen tension (pO2 less than or equal to 5 mm Hg). Neither the permeability nor the pO2 effects are observed in temperature-matched (+/- 0.05 degrees C), sham-exposed controls. In addition, at Tc, microwave exposure is observed to induce the shedding or release of two erythrocyte proteins not seen in sham-exposed controls. Moreover, the enhanced shedding of at least seven other proteins all of molecular weight less than or equal to 28,000 D was detected in the microwave-treated samples. Using sensitive silver staining we estimate that approximately 450 fg of protein were shed per erythrocyte. These results demonstrate that temperature and pO2 are important influences on both functional and structural responses of cell membranes to microwave radiation.