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 sensitivity to transformation in the cell cycle as originally proposed by Rossi and Kellerer(1) and takes into account the saturation observed at high doses with high and low LET radiation. Published fission spectrum neutron data, after acute irradiation in a wide dose interval from 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 alteration to give rise to transformation, N is the average number of energy deposition events per Gy in the sensitive site of the cell, s is the duration 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 weighted fit of 28 points were: alpha = 0, beta = 0.16 +/- 0.03 Gy-2, tau = 18 +/- 4 min and K = (730 +/- 94) x 10(-5), with a chi square value of 19. Assuming acute irradiation best fitted parameter values, transformation frequencies due to protracted or fractionated exposure were predicted and compared with experimental findings on fission and monoenergetic 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.