Effect of ionizing radiation on the transport of spin-labelled compounds across the porcine erythrocyte membrane

Using the transport of nitroxide spin labels as a method of estimating the permeability of erythrocyte membranes (Ross and McConnell 1975), an investigation was made of the effect of 60Co radiation (10 kGy/hour) on the transport of non-electrolytes TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), cation TEMPO-choline and anion 3-carboxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl across the porcine erythrocyte membrane. The sequence of transport rates was TEMPO, TEMPOL, the anion, and TEMPO-choline. An increase in the reduction of TEMPO was noted after a dose of 1 kGy. Changes in the reduction of TEMPOL were observed only after a dose of 2 kGy. An acceleration of TEMPO-choline reduction was brought about by a dose of 0.5 kGy, while enhanced reduction of anion was found at doses of 1-2 kGy. It was concluded that the spin-label method applied to studies of the effect of radiation on the transport of different compounds allows not only for determination of the rate of permeation of the molecules into the cells but also enables elucidation of species differences in the properties of cell membranes and in their sensitivity to the action of external factors. (U.K.)