The Effects of Steroid and Calcium Channel Blocker on Single High Dose Irradiation-induced Apoptosis in Rat Brain

ABSTRACT

OBJECTIVE: Radiation injury includes radiation necrosis and apoptosis. The purpose of this study is whether steroids and calcium channel blockers are effective for the prevention of single high dose irradiation-induced apoptosis in the rat brain. METHODS: Eighty Sprague-Dawley rats were divided into four experimental groups Control(nontreated, n=20), Dexamethasone-treated(0.1mg/kg, n=20), Prednisolone-treated(2mg/kg, n=20), Nimodipine-treated (0.5mg/kg, n=20). After drug was administered, the right hemisphere of rat's brain was exposed to a single 10Gy dose of gamma rays using Ir-192. All brains underwent histological examination at 1 week, 2 weeks, 4 weeks, and 8 weeks after irradiation to evaluate cortical thickness and number of apoptotic cells. Apoptotic cells were detected by TUNEL assay. RESULTS: In nimodipine-treated group, apoptotic cell count was reduced significantly, compared to that of control(non treated) group at 4 and 8 weeks after irradiation(p<0.05). The decrease of cortical thickness was reduced significantly in nimodipine-treated group, compared to that of control group(p<0.05). There was no significant changes in the number of apoptotic cells and cortical thickness in prednisolone and dexamethasone-treated groups compared with those of control. CONCLUSION: These results suggest that nimodipine treatment may have effects on the prevention of radiation-induced apoptosis. If it could be established that calcium channel blockers inhibit radiation injury, they might be useful in radiation therapy. Further investigation of calcium channel blockers including dosage effectiveness, intracellular calcium ion concentration and effects on tumor tissue are necessary to clarify the usefulness of nimodipine.