IN-VIVO PROTECTION BY CIMETIDINE AGAINST FAST NEUTRON-INDUCED MICRONUCLEI IN MOUSE BONE-MARROW CELLS

We have previously shown that cimetidine is capable of reducing the cl astogenic effect of gamma-rays. In this research the radioprotective p roperty of this drug was examined against low doses of fast neutrons u sing the miconucleus assay. Swiss albino male mice (12 weeks old) were irradiated by fast neutrons emitted from a Am-241-Be-9 source. The ab sorbed doses were 1.5, 2.25, 3.375 and 5.06 cGy at a dose rate of 0.71 8 cGy/h. Two hours prior to neutron irradiation mice were treated by c imetidine at a concentration of 15 mg/kg body weight injected i.p. Mic e were sacrificed by cervical dislocation at different post-irradiatio n times (24, 48 and 72 h). The results obtained show that the frequenc y of neutron-induced micronuclei in polychromatic erythrocytes (PCEs) is significantly higher than those of control groups (P < 0.05) at the neutron doses used in these experiments. Moreover, cimetidine effecti vely reduced (1.5-2-fold) the frequency of micronuclei in PCE (P < 0.0 5). These results show that cimetidine can protect bone marrow cells a gainst clastogenic effects of low dose fast neutrons and hence high li near energy transfer (LET) radiation. The mechanism by which cimetidin e reduces the clastogenic effects of fast neutrons is not fully unders tood. It might act through a free radical scavenging mechanism associa ted with the amplification of the glutathione system. Published by Els evier Science Ireland Ltd.