Respiratory mutant and liquid holding recovery inhibition in yeast cells

Cell ability to recover from radiation damage is of great relevance in cancer treatment. It is often believed that the inhibition of cell ability to the liquid holding recovery (LHR) may be an indicator of the overall suppression of cell ability to recover from potentially lethal radiation damage. However, the literature contains no experimental evidence whether the LHR inhibition may always serve as marker of the significant increase in cell sensitivity to damaging agents.
In experiments described here the yeast cells were used as a model for eukaryotic cells. The dose-response curves and recovery kinetics were determined by colony assay after simultaneous treatment of heat with ionizing or UV radiations as well as after the simultaneous action of ionizing radiation and cisplatin. The cell survival was estimated by both microscopic method and colony forming ability.
It is demonstrated that the recovery may take place on nutrient media. The complete inhibition of cell recovery after simultaneous heat treatment with ionizing radiation or UV light is accompanied with the significant increase in cell sensitivity to these agents, the actual increase being more appreciable than that expected after the inhibition of the LHR only. This rule is not universal as it was demonstrated for diploid yeast cells exposed to ionizing radiation and cisplatin.
The LHR takes place on nutrient media during the delay of the first postirradiation division. The LHR inhibition may not always indicate the suppression of other dark recovery processes and the corresponding increase in cell radiosensitivity.