The sensitivity of the in vitro cytokinesis-blocked micronucleus assay in lymphocytes for different and combined radiation qualities.
OBJECTIVE
The dose-response relationship and the relative biological effectiveness (RBE) for the induction of micronuclei in lymphocytes was analyzed after irradiation in vitro with a 6-MeV neutron beam that was followed by 240-kV X-rays. The dose range of the combined exposure comprised 1 to 3 Gy. For reference, the dose-effect relationships found after X-ray (0.5 to 5 Gy)- and neutron (0.5 to 4 Gy) exposure applied separately are presented. The possibility of an interaction between the 2 radiation qualities is investigated by the method of isobole calculation termed "envelope of additivity".


METHODS
Micronuclei were analyzed in PHA-stimulated, cytokinesis-blocked human lymphocytes.


RESULTS
The dose-response relationships for the micronucleus frequencies induced by the neutron irradiation, as well as by the mixed exposure, were linear. A saturation effect was indicated after neutron doses higher than 3 Gy. After low LET exposure the dose-response curves were describable by a linear-quadratic model. For neutron-induced micronucleus frequencies, RBE-values of 2 to 3 and for the combined exposure RBE values of 1.5 to 2 were calculated for a range of effect of 0.5 to 1.5 micronuclei/binucleated lymphocyte. No indication was found for an interaction between the damage induced by X-rays and that produced by neutrons under our experimental conditions.


CONCLUSIONS
These studies demonstrate a clear dependence of micronucleus induction on radiation quality and emphasize the usefulness of the micronucleus assay in biological dosimetry, also in cases in which high LET radiation or a mixed beam is involved as the radiation source.
Wuttke
K
K
Institut für Medizinische Strahlenbiologie, Universitätsklinikum Essen, Germany.
Müller
W U
WU
Streffer
C
C
D000328:Adult; D002455:Cell Division; D016001:Confidence Intervals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000528:radiation effects*; D008297:Male; D015162:Micronucleus Tests / Q000379:methods*; D009502:Neutrons; D016012:Poisson Distribution; D012680:Sensitivity and Specificity; D014965:X-Rays