No abstract

Naturally occurring radiation can be found all around us and account for most of the radiation received by human beings each year. Indonesia has a region with high-dose natural radiation located in the suburb of West Sulawesi province with a dose rate up to 2800 nSv/h; however, its impact was not fully understood. The aim of this study was to evaluate the radiosensitivity of 12 peripheral blood lymphocytes of inhabitant from high background radiation area (HBRA) and 10 from normal background radiation area (NBRA) based on cytokinesis-block micronucleus (CBMN) assay after challenged with 1.5 Gy of gamma ray. The analysis of CBMN was done according to standard procedure as per IAEA guidelines, and frequency of binucleate (mitotic) cells with micronuclei (MN) was scored in around 2000 binucleate lymphocytes cells per culture in microscopic analysis. Mean MN frequency for HBRA was lower than that of NBRA (0.121 vs. 0.189) after irradiation, indicating an adaptive response in HBRA group that resulted in less radiosensitivity; however, there was no statistically significant different ( P > 0.05) between these two groups. The MN number was higher in women compared to men for both HBRA (0.15 vs. 0.09) and NBRA (0.216 vs. 0.147) groups. Besides, there was no statistically significant difference ( P > 0.05) in Nuclear Division Index (NDI), as measured in 500 metaphase cells with published formula, between HBRA and NBRA samples (1.24 vs. 1.21). The lower MN frequency prompts us to conclude that there is an adaptive response in the lymphocytes of inhabitants as an indicator of lower radiosensitivity to the high natural radiation exposure. Further studies using large number of samples are required to obtain more comprehensive conclusion along with the assessment of other types of radiosensitivity-related biomarkers.

People living in high background radiation areas (HBRAs) possibly develop the radioadaptive response (RAR) phenomenon. The Mamuju area in West Sulawesi Indonesia is known as an HBRA in Indonesia due to its high natural uranium contents. It is possible that RAR has developed in Mamuju inhabitants. To prove this hypothesis, here in this study, evaluation of the individual radiosensitivity in the inhabitants of Takandeang Village, Mamuju, was conducted using G 2 micronucleus (MN) assay. Association between blood groups and TP53 Arg72Pro polymorphism with individual radiosensitivity was also evaluated in this study. Using G 2 MN assay, we assessed the individual radiosensitivity of Takandeang Village inhabitants and control samples. For each sample, three parameters were calculated. The spontaneous (baseline) MN number, MN number after 0.5 Gy in vitro irradiation, and radiation-induced MN were calculated to predict the individual radiosensitivity. The radiation-induced MN was defined by subtracting the spontaneous MN number from the MN number after irradiation. The mean and SD of the number of micronuclei induced by radiation found in control group (CG) was set as the cutoff value to determine the individual radiosensitivity in all samples. The occurrence of a radiation-induced MN value higher than the mean CG + 1SD CG was scored as 1, indicating a milder radiosensitive phenotype, whereas a result higher than the mean CG + 2SD CG was scored as 2, and indicated a more severe radiosensitive phenotype. When the individual value was lower than the mean CG + 1SD CG, a score of 0 was attributed to the tested subject. The results showed that four individuals in Takandeang Village inhabitants had a milder radiosensitive phenotype, while the others were categorized as normal radiosensitive. A similar finding was also found in control samples. Our study failed to find any correlation between radiosensitivity and either blood group or the TP53 Arg72Pro polymorphism. Overall, our study revealed the possibility of RAR phenomena in Takandeang Village inhabitants. Further investigation using a different point of radiation dose value and larger sample number should be performed to validate this study results.Journal homepage: http://aij.batan.go.id

The Mamuju area has recorded a higher than average natural radiation dose compared to other regions in Indonesia. It is possible that inhabitants of Mamuju developed the radioadaptive response (RAR). To prove that the RAR was developed in Mamuju inhabitants, evaluation of lymphocytic radiosensitivity using the G0 micronucleus (MN) assay was conducted herein. The MN frequencies in peripheral blood lymphocytes before and after exposed to 1.5 Gy radiation at a dose rate of 0.38 Gy/min were assessed from 11 samples of Botteng Village, Mamuju inhabitants and control groups. These treated cells were then cultured and exposed to cytochalasin-B to arrest cells during the cytokinesis stage. The mean number of MN induced by radiation per 1000 binucleated cells (BNC) was evaluated for both Mamuju inhabitants and control groups. The lymphocytic radiosensitivity was calculated using standard deviation (SD) of the mean value (MV) of the number of MN induced by radiation found in the control group. Based on the SD and MV values, individual lymphocytes were classified as ''resistant'', ''sensitive'', or ''normal'' if the mean of MN induced by radiation was ≤ MV -(2×SD), ≥ MV + (2×SD) or in between, respectively. The results showed that lymphocytes from six samples in Botteng Village inhabitants were categorized as resistant and five samples were normal. In contrast, all samples in the control group were demonstrated to have normal sensitivities. The study results also revealed that lymphocytic radiosensitivity was not correlated with age and gender, which was probably because of the small sample size used in this study. Further investigation with a larger sample number and higher radiation dose should be conducted to validate our findings.