American-Eurasian Journal of Toxicological Sciences 6 (1): 25-29, 2014 ISSN 2079-2050 © IDOSI Publications, 2014 DOI: 10.5829/idosi.aejts.2014.6.1.83259 Corresponding Author: Parinaz Mehnati, Department of Medical Physics, School of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran. Tel/Fax: +98-411-3364660. 25 Gamma-Radiation Induced Endoreplication in Exposed CHO Cell Line Parinaz Mehnati Department of Medical Physics, School of Medicine and Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Abstracts: Several studies have highlighted the possibility of radiation induced chromosomal aberrations. The present study explains the susceptibility of numerical and structural chromosomal alterations, specifically endoreplication in irradiated Chinese Hamster Ovary (CHO) cell line. A total of 426 metaphase spreads prepared from CHO cells, exposed to 2 or 6 Gy of Co -rays were analyzed. The frequency of dicentric chromosomes 60 was 48 %, endoreplications 12.6 % and acenteric fragments 12.7 %. The manifestation of endoreplication after exposure to ionizing radiation in comparison with control cells was significant. Also, dicentric chromosomes were appeared to be created in a dose-dependent manner and observed more frequently than acentric fragments. However, the dose-dependent effect of irradiation was not seen in the case of endoreplication. This study suggests the possible hazardous effect of radiation on spindle function, microtubule motor or structure, resulting in endoreplication. Key words: Gamma-Radiation Endoreplication CHO Cell Chromosomal Aberrations INTRODUCTION on animal cells have frequently shown that exposure of Radiation biology has been challenged with the in the incidence of numerical [3, 4] and structural genetic effects of radiation exposure in recent years. chromosome anomalies [5, 6]. A variety of cell types has These effects are attributed to the immediate, direct and been used to study the radiation-induced chromosomal targeted action of radiation on DNA. In the initiation damage and a cell dependent pattern of aberrations has stage of ionizing, radiation causes molecular damage by been detected. However studies on potential induced modification of the primary structure of DNA due to the numerical and structural chromosome anomalies in passage of the particle through the cell. The initial transmission to the next generations are appear to be radiation damage to the DNA structure could lead to inadequate [7]. specific biological lesion, such as chromosomal Duplication is a chromosomal rearrangement that aberration, genetic instability and mutation in a specific results in an increase in the copy number of a particulate somatic cell target [1]. Molecular damage is the result of chromosomal region, but endoreplication or deposition of the energy and production of ionized and endoreduplication is the replication of DNA during S excited state of the molecule’s physical events, radical phase of the cell cycle without subsequent completion of species and other molecular products in the environment mitosis or cytokinesis. It is one of the numerical of chemical events of the DNA. Goss and Harris [2] were chromosomal abnormalities and referred to duplicated described that ionizing radiation breaks chromosomes into number of all chromosomes including in respected cell. smaller fragments with sizes that are proportional to the A chromosomal base study on cultured human radiation dose. They explained that the closer two genes lymphocytes showed that a single dose of radiation are together more likely to segregate within a segment of causes the eventual endoreplication of many lymphocytes DNA following treatment with ionizing radiation. Studies even from any stage of interphase [8]. Although many of cells to ionizing radiation causes dose-dependent increase