TIME COURSE OF CEREBELLAR CATALASE LEVELS FOLLOWING NEONATAL IONIZING RADIATION EXPOSURE

L. G. CÁCERES; A. DI MEGLIO; F. M. SERRANO; L. M. ZIEHER; L. R. GUELMAN

Atlanta, Ga., USA

Congreso; 36th Annual Meeting of the Society for Neuroscience (SFN); 2006

Society for Neuroscience (SFN)

Time course of cerebellar catalase levels following neonatal ionizing radiation exposure L. G. Cáceres, A. Di Meglio, F. M. Serrano, L. M. Zieher and L. R. Guelman 1ª Cátedra de Farmacología, Facultad de Medicina, UBA and Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET). Email: lguelman@fmed.uba.ar   Reactive oxygen species (ROS) are physiologic products of normal metabolism that might increase in response to oxidant agents, such as ionizing radiations. Developing Central Nervous System (CNS) is vulnerable to ROS-mediated, ionizing radiation damage, being cerebellum (CE) especially sensitive. The aim of the present work was to test if the high susceptibility of developing CE to ROS-mediated, radiation-induced injury could be explained by an impairment of the cellular antioxidant defense system, in particular the activity of the antioxidant enzyme catalase, an heme protein that removes toxic hydrogen peroxide from the cell. Neonatal rats were X-irradiated in their cephalic ends and the levels of cerebellar catalase were measured at 15, 30, 60 and 90 days post-irradiation (PI). Results show a decrease in cerebellar total catalase activity in irradiated animals at 15 and 30 days PI (in % of control: 65.6 ± 14.8 and  51.35 ± 5.8, respectively), followed by a additional decline at 60 days PI (in % of control, 9.3 ± 0.34). However, at 90 days PI, a rise in cerebellar catalase levels was observed in irradiated animals (in % of control: 93 ± 17.8). These data suggest that, although at 15 and 30 days the decrease in cerebellar catalase activity of irradiated animals can be explained by the decrease in cerebellar weight, the subsequent greater decline in cerebellar catalase levels observed at 60 days could be due to a direct effect of radiation-induced oxidative damage on catalase itself. However, since cerebellar catalase levels rise at 90 days PI up to control values, it would be suggested that some compensatory mechanisms could be triggered to avoid the exacerbation of the oxidative stress. These data demonstrate a complex temporal time course of an antioxidant enzyme of a developing tissue following ionizing radiation exposure.