The Increased Passive Efflux of Sodium and Rubidium from Rabbit Erythrocytes by Microwave Radiation

The passive efflux rates of sodium-22 and rubidium-86 from the red cells of male New Zealand white rabbits were measured in vitro after 1-hr irradiations at 2.45 GHz. The temperature of the samples and the power absorbed were controlled. Arrhenius plots of measurements made in the absence of radiation exposure revealed that both the sodium and rubidium efflux have four separate linear regions with transitions at 8-13, 22.5, and 36°C. The efflux rates with microwave exposure were identical to the control rates, except at the critical temperatures, where irradiation increased the efflux of both cations. This response was examined at the 22.5°C transition at three specific absorption rates (100, 190, and 390 mW/g). At all three levels the cation efflux was statistically greater than one would predict from a strictly thermal response. The response does not increase monotonically as a function of absorbed power. Similar increased cation efflux was also observed near the 36°C and 8-13°C transitions. Possible mechanisms for this effect are discussed.