Effects of X Irradiation on Cell Kinetics in Cultured Rat Tooth Germ Cells.

Research Project

Project/Area Number	60480437
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	外科・放射線系歯学
Research Institution	Kagoshima University
Principal Investigator	NOIKURA Takenori Kagoshima University, School of Dentistry, 歯学部, 教授 (40102561)
Co-Investigator(Kenkyū-buntansha)	吉元絹代鹿児島大学, 歯学部, 教務職員 IKIMORI Rie Kagoshima University, School of Dentistry, 歯学部, 助手 (90176074) TOMOMURA Akito Kagoshima University, School of Dentistry, 歯学部附属病院, 助手 (60188810) KAWANO Kazunori Kagoshima University, School of Dentistry, 歯学部, 助手 (50108750) YOSHIMOTO Kinuyo Kagoshima University, School of Dentistry
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥6,600,000 (Direct Cost: ¥6,600,000) Fiscal Year 1986: ¥200,000 (Direct Cost: ¥200,000) Fiscal Year 1985: ¥6,400,000 (Direct Cost: ¥6,400,000)
Keywords	Tooth germ cell / Radiation effect / Cell cycle / Flow cytometry / 【G_2】ブロック
Research Abstract	Tooth germ of rat incisor was cultured in vitro and the epithel like cells were established. Cultured rat tooth germ cells ( RTG-2 ) and mouse fibroblastic cell lin ( L-5 cells ) were exposed to 2, 5 and 10 Gy of X-rays. The cellular DNA contents were measured by a flow cytometry and the effect of X irradiation was compared with the DNA histograms. The results were as follows, 1. In every dose group of asynchronous L cells, cell accumulation of <G_2> +M phases ( <G_2> block ) occured after irradiation. The histogram pattern of cells exposed to 2 Gy returned to the unirradiated one within 20 hours after irradiation. When the cells were exposed 10 Gy, cell accumulation into <G_2> +M phases persisted even at 30 hours after irradiation. After irradiation to synchronized cells in M phase, the cells were prevented from entering in S phase and the accumulation in <G_1> phase ( <G_1> block ) was observed. 2. RTG-2 cells showed slow growth and the doubling time was about 70 hours. DNA histogram of RTG-2 showed that the proportion of <G_1> , S and <G_2> +M phases were 66, 28 and 6%, respectively. When the RTG-2 cells were irradiated with 2 Gy of X-rays, cell accumulation in S phase was occured, indicating the <G_1> block and/or prevention of S phase from entering <G_2> phase. These results suggested the possibility of different mechanism between L-cells and slow proliferating RTG-2 cells as to the sensitivity to X irradiation.