The Radioprotective Activities of Turpentine-induced Inflammation and α_2-Macroglobulin : The Effect of Dexamethasone on the Radioprotective Efficacy of the Inflammation

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This work was aimed at the radioprotective efficacy of turpentine oil (TO), α_2-Macroglobulin (α_2-M), Amifostine (Ami) and/or dexamethasone (Dex). These agents were administrated, alone or in combination, prior to irradiation of rats with 6.7 Gy (LD_<50/30>). The survival was recorded daily for 4 weeks after irradiation and body weight, peripheral leukocytes and thrombocytes were measured. The plasma concentration of α_2-M and other acute phase proteins were determined by crossed immunoelectrophoresis. All rats receiving α_2-M and Ami alone or in combination survived the radiation injury, whereas the rate of survival of TO-treated rats was 90%. Radiation and therapy-induced changes in the expression of acute phase protein genes were atypical for the acute phase reaction. Dex alone was lethal for 45% and 55% of control and irradiated rats, respectively. Pretreatment with 1mg Dex reduced radioprotective efficacy of TO and Ami to 30% and 40%, respectively. Given together TO and Ami provided 70% protection to rats receiving Dex. The TO and α_2-M enhanced the rate of survival from 50% to 90% and 100%, respectively. In the presence of 1mg Dex the TOinduced radioprotectors and Ami exhibited radiosensitizing rather than radioprotecting activities.