Protection of Tissue-culture Cells against Ionizing Radiation

Summary

Protection against x-irradiation by hypoxia, glycerol, dimethyl sulphoxide, dimethyl sulphone, cysteamine and a combination of glycerol and cysteamine was investigated at + 20°c and −196°c. The protective power of the treatment was assayed as the degree to which it prevented radiation damage, i.e. the loss of the reproductive integrity of tissue-culture cells.

Using cells attached to a Melinex sheet the following dose-reduction factors (DRF) were found:

15 volume per cent glycerol, 1·9; 15 per cent glycerol + 4 mM cysteamine, 2·8; 0·5, 1, 2, 4, 6, 8, 15 and 30 volume per cent dimethyl sulphoxide, 1·13, 1·3, 1·36, 1·65, 1·58, 1·98, 2·3 and 2·4 respectively; 4 mM cysteamine, 1·9 and anoxia, 2·6. Dimethyl sulphone did not protect against irradiation.

Cells in suspension were protected against freezing and thawing by glycerol and dimethyl sulphoxide. Dimethyl sulphone showed no protective activity. Freezing to a temperature of −196°c made cells in suspension less sensitive to x-irradiation (DRF 1·9–2·8). In these conditions 15 volume per cent glycerol, 1 and 4 volume per cent dimethyl sulphoxide and a combination of 15 per cent glycerol and 4 mM cysteamine gave the same DRF at room temperature and at −196°c (if survival was compared with controls irradiated at the same temperature). However, if for hypoxia similar calculations were made, a much better protection was found at room temperature than at −196°c (DRF 2·2 and 1·1).