TRANSFORMATION-INDUCED IN C3H10T1 2 CELLS EXPOSED TO HIGH-LET RADIATIONS - AN INTERPRETATION OF THE PUBLISHED DATA/

Transformation frequencies induced in C3H10T1/2 cells exposed to acute and protracted doses of high LET radiations were analysed. The model used is based on the assumption that there is a brief period of high s ensitivity to transformation in the cell cycle as originally proposed by Rossi and Kellerer(1) and takes into account the saturation observe d at high doses with high and low LET radiation. Published fission spe ctrum neutron data, after acute irradiation in a wide dose interval fr om 0.05 to 5 Gy, were fitted to the equation T(D) = K[tau/s(1 - e(-ND) ) + s-tau/s(1 - e(-alphaD-betaD2)] where the two terms in parentheses represent the alteration probability for cells within and outside the sensitive period, respectively. K is the probability for the alteratio n to give rise to transformation, N is the average number of energy de position events per Gy in the sensitive site of the cell, s is the dur ation of the cell cycle and tau is the duration of the period of high sensitivity in the cell cycle. The parameter values obtained from a we ighted fit of 28 points were: alpha = 0, beta = 0.16 +/- 0.03 Gy-2, ta u = 18 +/- 4 min and K = (730 +/- 94) x 10(-5), with a chi square valu e of 19. Assuming acute irradiation best fitted parameter values, tran sformation frequencies due to protracted or fractionated exposure were predicted and compared with experimental findings on fission and mono energetic neutrons and on charged particles of LET between 40 and 150 keV.mum-1. The model's predictions were found to be closely consistent with the available experimental data.