Effects of Dose Rate on Response of Synechococcus lividus to Very Low Doses of Chronic γ Radiation: Influence of Enzymatic Equipment of Starting Cells

• Published in: Radiation research 1986-03, Vol.105 (3), p.379-386
• Main Authors: Conter, A., Dupouy, D., Planel, H.
• Format: Article
• Language: English
• Subjects: Cell growth; Cellular metabolism; Cultured cells; Dehydrogenases; Enzymes; Inoculation; Ionizing radiation; Irradiation; Radiation dosage; Superoxides
• ISSN: 0033-7587; 1938-5404
• DOI: 10.2307/3576693

The effects of chronic γ irradiation at dose rates ranging from 1.50 to 74.5 mGy/year on cell proliferation of Synechococcus lividus in culture are studied. Responses are different when medium is inoculated with cells selected from different cultures in different phases of growth. Cells in deceleration phase and early stationary phase are stimulated when resuspended in fresh medium and chronically irradiated up to 31 mGy/year, while cultures inoculated with log cells are inhibited when irradiated with chronic γ radiation. Determination of enzymatic activities shows that a stimulatory effect occurs only for cells that present oxidative stress manifested by high protective enzyme activities (superoxide dismutase and glutathione reductase) and respiratory activity (glucose-6-phosphate dehydrogenase). The stimulatory effect disappears when the dose level received by the cells becomes too high compared to enzymatic equipment. An inhibitory effect occurs in log cells that present low protective enzyme activities and high photosynthetic activity. Results suggest that metabolism of cultures at the inoculation is very important in the mechanism of adaptation to very low doses of chronic γ radiation.