Inhibition of the adaptive response of human lymphocytes to very low doses of ionizing radiation by the protein synthesis inhibitor cycloheximide

When human lymphocytes are preirradiated with 1 cGy of X-rays, the cells become less sensitive to subsequent exposures to high doses of about 150 cGy in that approximately one-half as many chromatid aberrations are induced as expected. This adaptation has been attributed to the induction of repair enzymes (proteins) some 4-6 h after the initial low-dose exposure. Experiments have now been carried out showing that application of the protein synthesis inhibitor cycloheximide at this time, but not earlier, prevents the adaptive response.