Irradiation of Primary Human Amnion Cell Cultures: Effects on DNA Synthesis and Progression through the Cell Cycle

Abstract

The effects of radiation on progression through the life cycle were studied in very slowly proliferating, morphologically pure, cells derived directly from normal human tissue. Owing to a low mitotic activity balanced by some cell loss, these cells could be maintained for 2 months in the same culture tubes without wide changes in net cell count. During the first 3 weeks of growth the population consisted primarily of slowly proliferating cells in which S and G2 were relatively short fixed phases of the life cycle, each lasting less than 24 hours. Because the estimated generation times averaged 14-20 days, most cells were in the presynthetic G1 phase. The most prominent finding which differentiated the response of these cells from that of rapidly proliferating mammalian cells was the marked radiosensitivity of the initiation of DNA synthesis. There was a dose-dependent decrease in the rate of flow of G1 cells into S with 10-100 R, and progression was almost completely stopped for 3-10 days by 300-1000 R. O...