MARKED REDUCTION OF RADIATION-INDUCED MICRONUCLEI IN HUMAN BLOOD-LYMPHOCYTES PRETREATED WITH MELATONIN

Human peripheral blood lymphocytes which were pretreated in vitro with melatonin, an endogenously synthesized pineal hormone, for 20 min at 37 +/- 1 degrees C exhibited a significant and concentration-dependent reduction in the frequency of gamma-radiation-induced micronuclei com pared with irradiated cells which did not receive the pretreatment. Th e extent of the reduction observed with 2.0 mM melatonin was similar t o that found in lymphocytes pretreated for 20 min with 1.0 M dimethyls ulfoxide, a known free radical scavenger, These observations indicate that melatonin may have an active role in protection of humans against genetic damage due to endogenously produced free radicals, and also m ay be of use in reducing damage due to exposure to physical and chemic al mutagens and carcinogens which generate free radicals. (C) 1995 by Radiation Research Society