EFFECTS OF EXPOSURE TO RADIOACTIVE 56MnO2 POWDER ON HYALURONAN SYNTHASE 2 IN THE LUNGS OF RATS.

: Manganese-56 (56Mn) is among the predominant radioisotopes produced in soil by neutrons from atomic bombs. Previously, we examined the effects of the internal exposure of this radioisotope in Wistar rats and reported significant pathological changes in the lung and small intestine. In the present study, we focused on its effects on hyaluronan synthase 2 (Has2) gene expression that may related to pathological changes in the lung. Ten-week-old male Wistar rats were exposed to neutron-activated 56MnO2 powder, non-radioactive MnO2 powder or external 60Co γ-rays (2 Gy, whole body). Animals were examined on days 3, 14, and 60 post-exposure. Absorbed doses in the lung of rats exposed to 56Mn were 55-110 mGy. Quantitative reverse transcription polymerase chain reaction analysis revealed that 56Mn exposure significantly reduced the expression of Has2 gene in the lung, while γ-rays did not change it. Our findings suggest that internal exposure to 56Mn, even at low doses, has a significant biological impact on the lung compared with external radiation.