INFLUENCE OF X-RAY DOSE AND TIME OF ITS DELIVERY IN-VITRO ON YIELD OF CHROMOSOMAL ABERRATIONS IN PERIPHERAL BLOOD LYMPHOCYTES

The relationship was studied between the x-ray dose and yield of chromosomal aberrations in human lymphocytes irradiated in vitro and examined in metaphase 51 hours after initiation of the culture. The doses ranged from 30 to 415 rads, delivered at two dose-rates: ∼ 110 and ∼ 16 rads/min. Frequency of the aberrations (yi) versus dose (x) were described using two types of regression function: yi = αixβi + ci and yi = a1x + a2ix2 + ci. At high dose-rate, the power function exponent for dicentric chromosomes of 1·23 ± 0·13 was observed; at the dose rate of 16 rads/min the exponent was not significantly different from unity. In the quadratic equation, lowering of the dose-rate was followed by reduction in the contribution of the dose-square term roughly by an order of magnitude; a similar observation was made with respect to other aberrations (rings, acentric fragments and intercalary deletions). The effect of irradiation-time (from 3 up to 453 min) on the aberration yield after a constant dose of 301 rads was studied. Beginning with 5 min, further stretching of the time did not affect the frequency of dicentrics and rings, but was accompanied by a significant reduction of the yield of intercalary deletions and acentrics. © 1969 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.