[Effects of x-rays on guinea pig cells cultivated in vitro. II. Influence of environmental factors on survival].

Various factors influencing radiosensitivity of cells of the RCP strain of guinea pigs were investigated. The number of colonies arising from cells exposed to 0-, l00-, a rate of 150 r/min, did not differ significantly, although at the three highest doses approximates 10% fewer colonies formed, compared to unirradiated cultures. The number of colories formed from cells irradiated with 300 r declined progressively as the number of cells in the irradiated culture increased from 10/sup 3/ cells/ml to 10/sup 6/ cells/ml. Fewer cells survived irradiation at 37 deg C than at 5, 13, 21, or 29 deg , but there was no difference in the survival rate of celis irradiated at the four latter temperatures. Cells irradiated in the presence of air showed approximates 0% reduction in survival compared to unirradiated cells; however, in the presence of nitrogen, survival of irradiated and unirradiated cells was similarly depressed. Fewer cells survived when irradiated in the stationary growth phase than in the logarithmic phase, indicating relatively greater radiosensitivity of metabolically inactive cells. (BBB)