In vitro radioprotective effects of histamine H2 receptor antagonists against gamma-rays induced chromosomal aberrations in human lymphocytes

Background: Radioprotective capability of histamine H2 receptor antagonists have been shown in several in vivo studies mainly using animal models. However, to verify the effectiveness of these agents in clinical applications, studies should be performed on human cells. In the present study radioprotective properties of these agents was examined in vitro on human lymphocytes using metaphase analysis. Materials and Methods: In vitro metaphase analysis technique was used to test the effects of cimetidine, ranitidine and famotidine on radiation induced clastogenic effects. Lymphocytes in whole peripheral blood were exposed to 3 Gy gamma-rays at a dose rate of 73.7 cGy/min in the presence or absence of various doses of the drugs used in this study. The frequency of chromosomal aberrations were determined after standard metaphase preparations and staining slides in 5% Giemsa. Results: Results show that radiation produced a high number of chromosomal aberrations in lymphocytes compared to controls (p<0.001). All three drugs used in this study effectively reduced the frequency of chromosomal aberrations at all doses. Famotidine was found to be more effective than the other two drugs. Conclusion: From the results obtained it can be concluded that H2-receptor antagonists used in this study effectively reduced the clastogenic effects of radiation with a dose reduction factor (DRF) of 1.5-2 in human lymphocytes in vitro. The way in which these drugs reduce the clastogenic effects of radiation might be via radical scavenging mechanism. Iran. J. Radiat. Res.; 2003; 1(2): 99 – 104.