Flowcytometric studies of effects of heat on DNA synthesis in different thermosensitivities mammalian cell lines

The effect of heat on DNA synthesis in HeLa S3 cells and L-5 cells was studied using flowcytometry. When D(0) values obtained from survival curves of Ehrlich ascites tumor cells, L-5 cells, HeLa S3 cells and NIH3T3 cells after heating to 43, 44, or 45℃, were compared, HeLa S3 cells were resistant and L-5 cells were sensitive to heating. During heating at 43℃, DNA synthesis (BUdR uptake) of HeLa S3 cells was resistant compared to that of L-5 cells. When the period of DNA synthesis was divided into 3 fractions (early S, mid S and late S), late S phase was the most sensitive fraction to heating at 43℃ for 60 minutes. From these results, relationship between DNA synthesis and thermocytotoxic effects are discussed.

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