| Popis: |
It is now well established that the loss of proliferative capacity of mammalian cells exposed to either X-rays or ultraviolet light (UVL) is dependent on the phase of the cell cycle occupied by the cells at the time of irradiation (1-4). Erikson and Szybalski (1), using the D98/AG cell line derived from human sternal marrow, found that the loss of proliferative capacity after exposure to either X-rays or UVL decreased as the cells progressed through the phase of DNA synthesis (S phase), but, as the cells left the S phase and approached mitosis, the response to X-rays increased, whereas the response to UVL reached a minimum value. Similar results were reported by Sinclair and Morton (2) for the V79 line of Chinese hamster cells. It thus appears that the patterns of response to UVL and X-rays may differ. Results obtained by Whitmore et al. (3) with X-rays indicated that the pattern of response is also dependent on the cell line used and the dose of radiation to which the cells are exposed. For low doses (greater than 5 % survival) there is a maximum survival in the middle of S phase. For higher doses of radiation this maximum in survival decreases, and a minimum appears at the end of S or at the beginning of G2. It was of interest, therefore, to determine the pattern of response of L cells to UVL at different stages in the cell cycle and to compare this pattern with that obtained with X-rays. The results of these experiments provide the basis for this report. The data indicate that the pattern of response of L cells to UVL is similar to that reported for the D98 and V79 cell lines, and confirm that the patterns of loss of proliferative capacity of cells exposed to UVL differ from those obtained for X-rays. |
