In vitro radiation-induced effects on rat tracheal epithelial cells. II) Different preneoplastic cell transformation after alpha and gamma irradiations.

In order to compare the cell transformation induced by alpha- and gamma-irradiation, primary cultures of tracheal epithelial cells from two rat strains, Sprague Dawley (SD) and Wistar Furth/Fisher F344 (WF/Fi) rats, were irradiated with 241Am alpha-particles or 60 Co gamma-rays. The relative transformation frequency (RTF) for WF/Fi primary cells was very close to the level of the spontaneous incidence and independent on the two irradiation types used. On the contrary, the RTF for the SD primary cells increased with a decrease of the LET radiation when the relative survival was higher than about 40%. Therefore, the RTF values reached 4-5 for alpha-particles and 10-12 for gamma-rays. The RTF can be related to the intrinsic radiosensitivity of the rat epithelial cells. However, the difference in the radiation-induced RTF for SD or WF/Fi primary cells seems to be due to the development, under genetic control, of the initial lesion to the neoplastic state.