The sheep red blood cells (SRBCs) were labelled with a concanavalin A-luminol-bovine serum albumin conjugate specific for the transmembrane anion transport protein (Band 3; i.e. the conjugate binds to Band 3). The band 3 transmembrane protein is the predominant membrane transport protein in red blood cells and plays a central role in structure and function of those cells.
The authors consider a mechanism involving the anion (superoxide) channel (composed of dimeric units of the transmembrane protein Band 3) and membrane-associated haemoglobin and enzymes.
Following exposure to microwave or air heating, the decrease in residual chemiluminescence was measured as an indication of oxidase activity (important in the oxygen release process from haemoglobin). The source of the chemiluminescence is the oxidation of luminol (of the conjugate) by superoxide, hydrogen peroxide and, perhaps, hydroxyl-free radical formed during the thermally induced autoxidation of oxyhaemoglobin; superoxide escapes the erythrocytes through the anion channel (composed of dimeric units of the transmembrane protein Band 3; see above).
The temperature was held constant at 25, 37, 40, 42 or 45°C.
|Exposure duration||10 min|
Air heating resulted in a significant decrease in residual chemiluminescence at temperatures above 37°C. Microwave radiation inhibited the decline in residual chemiluminescence above 37°C (at 45°C the inhibition was 40%).
The results suggest microwave irradiation either reversibly altered the thermodynamics of oxygen binding to haemoglobin or failed to energize a significant portion of the haemoglobin molecules to the thermal threshold of haemoglobin autoxidation.
The release of superoxide and peroxides from red blood cells in small blood vessels subjected to hyperthermia could result in oedema and an influx of granulocytes into surrounding tissues. Microwave radiation, with exposure parameters based on these results, is expected to minimize these effects.