MORPHOLOGICAL CHARACTERIZATION OF THE RADIATION-SENSITIVE CELL-LINE, XRS-5

Morphometric analysis was performed on the radiation sensitive Chinese hamster ovary (CHO) xrs-5 cell line, reverting xrs-5 cells and parent al K1 cells. Several ultrastructural parameters (increased nuclear env elope membrane separation, cell and nuclear volume, nuclear to cytopla smic ratio, and the nuclear surface area per unit volume of the cell) were measured and correlated with radiation sensitivity. A trend in in creased cell size and radiosensitivity was observed. However, only the substantially increased nuclear envelope membrane separation in sensi tive xrs-5 cells significantly correlated with radiation sensitivity. The maximal nuclear envelope membrane separation in sensitive xrs-5 ce lls was 270.8 nm. The maximal K1 cell nuclear envelope membrane separa tion was 134.8 nm, although, on average the KI cell nuclear envelope m embrane separation was 36.8 mm. The reverted xrs-5 cells had a smaller nuclear envelope membrane separation (maximal 83.6 nm), but the measu red space did not completely revert to that for K1 cells. Therefore, w e conclude that the nuclear envelope membrane separation is correlated with radiation sensitivity of xrs-5 cells, but it cannot be considere d as the only defect correlatable with the radiation sensitivity.