A Biochemical Study of the X-Radiation-Induced Inhibition of Sodium Transport (Na Pump) in Human Erythrocytes

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Abstract
In human erythrocytes under aerobic conditions, glycolysis is not decreased during the first hour after X-irradiation with 890 to 8900 rads. A slight increase is observed after larger doses:[image]20% and [image]35% after 4450 rads and 8900 rads, respectively. The ATP, ADP, and AMP content of the cells 1 hour after 890 rads or 1780 rads is not changed; 4450 rads and 8900 rads induce a decrease of ADP and AMP which is accounted for by an increase in ATP content. The ATPase activity of membranes of erythrocytes consists of 2 components. The 1st requires the presence of Mg, occurs in the absence of Na and K, and it is not inhibited by cardiac glycosides. This component is slightly impaired by x-rays:[image] 31% decrease after 8900 rads. The 2nd component requires Mg, NaandK; it is inhibited by cardiac glycosides,and corresponds to the mechanism of the Na pump in the membrane. This component is more radiosensitive, and its curve of inhibition coincides with the curve of inhibition of active Na transport (Na pump) in intact erythrocytes; the dose-effect curve can be decomposed into 2 pure exponential functions of dose, with D37 740 rads and 10,700 rads. X-rays inhibit active Na-transport by interfering with the "pumping" mechanism in the membrane.