Effects of 60Co gamma ray on MAO activity in rat brain

The effects of brain irradiation on the enzyme activity of MAO and the level of catecholamine were examined in whole brain of male rat. They were determined immediately after, 1, 2, and 3 hours after irradiation of 60Co γ ray. After irradiation of 1000 rad, MAO activity was significantly increased. However, no significant change was found after irradiation of 500 and 2000 rad. The catecholamine level did not change significantly after exposure to 1000 rad of 60Co γ ray. These results may that indicate increased MAO activity caused no significant change of catecholamine level because its level was regulated by the rate of not only degradation by MAO but also catecholamine synthesis. In 1000 rad irradiation, MAO was much activated by using β-phenylethlamine (β-PEA) than serotonin as substrates. This represents MAO-B was much activated than MAO-A, because β-PEA is specific substrate of MAO-B and serotonin is that of MAO-A. This result may represent MAO-B is much affected py free radical of irradiation because MAO-B is situated closer to peripheral hydrophoric region than MAO-A. (author)