Temperature‐specific inhibition of human red cell Na + /K + ATPase by 2,450‐MHz microwave radiation

The ATPase activity in human red blood cell membranes was investigated in vitro as a function of temperature and exposure to 2,450‐MHz continuous wave microwave radiation to confirm and extend a report of Na + transport inhibition under certain conditions of temperature and exposure. Assays were conducted spectrophotometrically during microwave exposure with a custom‐made spectrophotometer‐waveguide apparatus. Temperature profiles of total ATPase and Ca +2 ATPase (ouabain‐inhibited) activity between 17 and 31 °C were graphed as an Arrhenius plot. Each data set was fitted to two straight lines which intersect between 23 and 24 °C. The difference between the total and Ca +2 ATPase activities, which represented the Na + /K + ATPase activity, was also plotted and treated similarly to yield an intersection near 25 °C. Exposure of membrane suspensions to electromagnetic radiation, at a dose rate of 6 W/kg and at five temperatures between 23 and 27 °C, resulted in an activity change only for the Na + /K + ATPase at 25 °C. The activity decreased by approximately 35% compared to sham‐irradiated samples. A possible explanation for the unusual temperature/microwave interaction is proposed.