title: Induction of proline prototrophs in CHO-K1 cells by heavy ions.
abstract: Using an established mammalian cell line, Chinese hamster ovary cells (CHO-K1), we have observed the induction of prototrophs by various heavy ions. This cell line requires proline for normal growth in medium with low serum concentration. X-rays, three types of heavy particles (600 MeV/u iron, 670 MeV/u neon, and 320 MeV/u silicon ions), ethylmethane sulphonate and 5-azacytidine were used to induce revertants which were proline independent. Log-phase cells treated with 5-azacytidine showed a very high reversion frequency. The induction frequency per viable cell appears to be dose dependent for these four types of radiation, and the dose-response curves are approximately linear. Our results also indicate that the effectiveness of high-LET particles in inducing proline prototrophs is much greater than that of low-LET radiation. The RBE value for the induction of prototrophs was calculated for neon, silicon, and iron particles and found to be about 1.3, 1.7 and 4.5, respectively. At equal survival level, the reversion frequency for X-rays and EMS was about the same.
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000494:pharmacology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured / Q000528:radiation effects; D006224:Cricetinae; D003412:Cricetulus; D004601:Elementary Particles; D004735:Energy Transfer; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D005260:Female; D009154:Mutation; D010053:Ovary; D010315:Particle Accelerators; D011392:Proline / Q000378:metabolism / Q000528:radiation effects*; D012062:Relative Biological Effectiveness; D013997:Time Factors
chemical_list: D011392:Proline; D005020:Ethyl Methanesulfonate; D001374:Azacitidine