| Abstract: | The response of cultured CHO cells to U.V.L. irradiation during treatment with anisotonic solutions shows that treatment with hypotonic sucrose, NaCl or KCl solutions causes an increase in the cellular U.V.L. sensitivity, while exposure to hypertonic solutions causes a large decrease in U.V.L. sensitivity. Cells exposed to 1.8 M sucrose, NaCl or KCl solutions and given a U.V.L. dose of 252 erg/mm2 towards the end of the 20 min solution exposure time have survival levels which are respectively 228,26, and 23 times higher than the controls, i.e. cells irradiated in phosphate buffered saline. Cell volume data obtained using a Coulter counter, and nuclear area data of attached cells obtained using an optical microscope with a micrometer reticle, show that cell and nuclear size are related to U.V.L. sensitivity. That is, as cells shrink and the nuclear area decreases, the cells become more U.V.L.-resistant. During hypotonic treatment with 0.1 M NaCl, the cell volume, nuclear area and U.V.L. sensitivity increased in the first 2 to 4 min of exposure time, but at longer exposure times (greater than 3 to 4 min), cell volume, nuclear area and cellular U.V.L. sensitivity decreased. For 0.1 M KCl treatment the cells initially displayed a rapid increase in volume, nuclear area and U.V.L. sensitivity, but at the longer exposure times no decrease in cell and nuclear size were observed, and a slight increase in U.V.L. sensitivity occurred. Changes in U.V.L. sensitivity were related to changes in nuclear size and cell volume; however, calculations showed that during hypertonic treatment there is an ionic effect as well as an osmotic effect. That is, the cellular U.V.L. survival in equal hypertonic concentrations of NaCl or KCl was lower than in the same concentration of sucrose. |
