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 parental K1 cells. Several ultrastructural parameters (increased nuclear envelope membrane separation, cell and nuclear volume, nuclear to cytoplasmic ratio, and the nuclear surface area per unit volume of the cell) were measured and correlated with radiation sensitivity. A trend in increased cell size and radiosensitivity was observed. However, only the substantially increased nuclear envelope membrane separation in sensitive xrs-5 cells significantly correlated with radiation sensitivity. The maximal nuclear envelope membrane separation in sensitive xrs-5 cells was 270.8 nm. The maximal K1 cell nuclear envelope membrane separation was 134.8 nm, although, on average the K1 cell nuclear envelope membrane separation was 36.8 nm. The reverted xrs-5 cells had a smaller nuclear envelope membrane separation (maximal 83.6 nm), but the measured space did not completely revert to that for K1 cells. Therefore, we conclude that the nuclear envelope membrane separation is correlated with radiation sensitivity of xrs-5 cells, but it cannot be considered as the only defect correlatable with the radiation sensitivity.