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  • Title: The sensitivity of the in vitro cytokinesis-blocked micronucleus assay in lymphocytes for different and combined radiation qualities.
    Author: Wuttke K, Müller WU, Streffer C.
    Journal: Strahlenther Onkol; 1998 May; 174(5):262-8. PubMed ID: 9614955.
    Abstract:
    PURPOSE: 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.
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