Study of dose-rate and split-dose effects on the in vitro micronucleus yield in human lymphocytes exposed to X-rays.
This paper reports the effects of changes in dose-rate and dose-fractionation on the micronucleus (MN) yield in human lymphocytes exposed to 250 kV X-rays. For the investigation of dose-rate effects whole blood samples of four healthy donors were irradiated with doses ranging from 1 to 4 Gy given at various dose-rates between 0.2 and 40 Gy/h. For the higher doses (3 and 4 Gy) a decline in the MN yield became apparent when the dose-rate was reduced below 1.6 Gy/h. This effect was enhanced systematically by a further lowering of the dose-rate. For lower doses (1 and 2 Gy) the reduction in the MN yield was less pronounced: only a small effect was observed for two donors when a dose of 2 Gy was administered at a dose-rate of 0.2 Gy/h. In the split-dose experiment a dose of 4 Gy was delivered either as a single exposure or in two fractions of 2 Gy, separated by time intervals ranging from 30 min to 10 h. A continuous decrease of the MN yield with increasing interfraction time is observed: after an initial fast decline a further slight reduction in the MN yield occurs. The observed dose-rate and split-dose effects on the MN yield can be attributed to repair of sublethal damage.
Laboratory for Histology, University of Gent, Belgium.
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Vral
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Thierens
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De Ridder
D002869:Chromosome Aberrations; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000528:radiation effects*; D015162:Micronucleus Tests; D011829:Radiation Dosage; D011831:Radiation Genetics; D013997:Time Factors