Changes in the activity of acetylcholinesterase and Na,K-ATPase in human erythrocytes irradiated with X-rays.

The response of human erythrocytes to X-rays in the dose range from 40 Gy to 600 Gy was determined on the basis of changes in the activities of AChE and ATPase. The Na,K-ATPase activity increased above the control value at doses below 200 Gy, while at the doses higher than 200 Gy, it decreased, reaching 96% of the control value at a dose of 600 Gy. In the range of doses up to 200 Gy, the AChE activity, expressed as Vmax, did not change. At higher doses, it fell drastically, reaching 33% of the control value at a dose of 600 Gy. Simultaneously, the enzyme substrate affinity decreased at 200 Gy, and then started to increase at lower values of Vmax. The obtained results suggest that under appropriate conditions, low doses of radiation may have the opposite effects to high doses.