Metalloporphyrin antioxidants ameliorate normal tissue radiation damage in rat brain

Purpose: We examined the effects of manganese (III) meso-tetrakis (diethyl-2-5-imidazole) porphyrin, a metalloporphyrin antioxidant (MPA), on neural tissue radiation toxicity in vivo and on tumour cell radiosensitivity in vitro.Materials and methods: MPA was administered directly into the right lateral ventricle of young adult, male Sprague-Dawley rats (0 or 3.4 μg) 3 h before treatment with a single fraction, 100 Gy radiation dose delivered to the left brain hemisphere. The effects of treatment on radiation responses were assessed at different time points following irradiation.Results: MPA treatment prior to brain irradiation protected against acute radiation-induced apoptosis and ameliorated delayed damage to the blood-brain barrier and radiation necrosis, but without producing a discernible increase in tissue superoxide disumtase (SOD) activity. In vitro, MPA pretreatment protected against radiation-induced apoptosis in primary neuronal cultures and increased clonogenic survival of irradiated rat gliom...