Melatonin may play a role in modulation of bax and bcl-2 expression levels to protect rat peripheral blood lymphocytes from gamma irradiation-induced apoptosis

► Exposure to gamma irradiation increased the expression of bax. ► Exposure to gamma irradiation decreased the expression of bcl-2. ► Melatonin pretreatments reduced the percentage of apoptotic lymphocytes. ► Melatonin pretreatments modified the expression of bax and bcl-2. ► Melatonin pretreatment may improve the therapeutic index in radiation oncology.