Biological dosimetry of absorbed radiation by C-banding of interphase chromosomes in peripheral blood lymphocytes.

Induction of premature chromosome condensation enables direct observation of radiation-induced cytogenetic damage in non-stimulated, interphase, human peripheral blood lymphocytes. This phenomenon can be explored in radiation protection for biological dosimetry in instances of accidental exposure to ionizing radiation. Quantification of an exposure by means of this approach has been limited so far mainly to the analysis of chromosome fragments. This limitation is due to the fact that conventional Giemsa staining of prematurely condensed chromosomes (PCCs) does not allow visualization of the centromeric regions and, as a result, the identification of dicentrics, centric rings and acentric fragments. In the present report a C-banding procedure, refined to avoid swelling and chromosome distortion of freshly prepared PCCs spreads, is used to identify such aberrations in non-stimulated human lymphocytes. The method allows immediate banding of the centromeric regions and enables scoring of aberrations within a time interval (3-4 h after blood sample withdrawal) that is only a fraction of that normally required when cells stimulated to proliferate are analysed at metaphase. The dose-response for dicentrics and centric rings measured in interphase lymphocytes was found to be similar to that obtained at metaphase. Measurement of dicentrics and centric rings in prematurely condensed chromosomes of human lymphocytes would provide valuable information on radiation dose estimates, especially in cases of extreme urgency.