Study On The Effects Of Low Dose Rate⁶⁰Co γ/neutron Irradiation On The Rats

【Objective】To observe the low dose radiation （LDR）-induced radiation injuries, and uncover themechanisms of LDR-induced lipid metabolism disorder for the potent protection.【Materials and methods】SD rats were divided into4groups （12subgroups）, including control group, neutrongoup （N group）,⁶⁰Co γ group （γ group） and⁶⁰Co γ/neutron rays co-irradaiation group （Cogroup）. Animals in radiation groups accepted neutron irradiation （0.085mGy/h,21h/d）,⁶⁰Co γ irradiation （0.09Gy/h,2h/d）, or⁶⁰Co γ/neutron co-irradaiation respectively. In14d,28d and45d after irradiation, rats were sacrificed and the parameters of peripheralhematological cells, main organ index, bone marrow DNA, the proliferative responseability of spleen lymphocyte to mitogen ConA, sperm count, LPS content,the activity ofSOD and content of MDA content in the serum were detected. Additionally, LDR-inducedlipid metabolism disorde were detected, and RT-PCR was used to detect he mRNAexpression of FABP1, CYP7A1and PPARα.【Results】1. Effects of low-dose rate neutron radiation exposure（1） The influence of LDR neutron radiation on body weight.Body weight significantly decrease after28d and45d exposure （P<0.05）.（2） The influence of LDR neutron radiation on digestive system.Compare with the blank control group, intestinal length decrease （P<0.05或P<0.01）, LPS content showed a rising trend（P＞0.05）, liver index weresignificantly increases after28d and45d, exposure.（3） The influence of LDR neutron radiation on hematological system.Bone marrow DNA content OD values of radiation groups showed adecreasing trend. Compare with the blank control, WBC, RBC and PLT weredecreased in radition groups.（4） The influence of LDR neutron radiation on immunologic system Thymus index and spleen index decrease after45d exposure （P<0.01）.ConA-induced lymphocyte transformation rate decrease after14d and28dexposure （P<0.01）（5） The influence of LDR neutron radiation on genital systemTesticular index showed a decreasing trend（P＞0.05）, epididymis index andsperm relative count decrease in radition groups than in those of blank control（P<0.05）.（6） The influence of LDR neutron radiation on antioxidant systemCompare with the blank control group, SOD content of irradiaton groupsshowed a decreasing trend（P＞0.05）, However, MDA activity increase after14dand28d exposure （P<0.05or P<0.01）.（7） The influence of LDR neutron radiation on lipid metabolismRT-PCR assay found that the expressions of CYP7A1were significantlylydecreased.in radiation groups, the expressions of irradiation groups were0.488times,0.276times and0.156times than those of the blank chontrol group. After45d,exposure, the expressions of PPARα was2.701times than those of the blankchontrol group. Differences were’t detected in the expressions of FABP1.2. Effects of low-dose rate⁶⁰Co γ ray radiation exposure（1）The influence of LDR⁶⁰Co γ ray radiation on body weight.Body weight significantly decrease after28d and45d exposure （P<0.05orP<0.01）.（2） The influence of LDR⁶⁰Co γ ray radiation on digestive systemIntestinal length decrease after28d exposure （P<0.01）, LPS contentsignificantlyly increase after45d exposure （P<0.01）, liver index significantlyincrease after28d and45d, exposure （P<0.05or P<0.01）.（3） The influence of LDR⁶⁰Co γ ray radiation on hematological systemBone marrow DNA content OD values of radiation groups significantlydecrease （P<0.05or P<0.01）, Compare with the blank control, WBC, RBC and PLTwere decreased in radition groups after28d and45d exposure （P<0.05or P<0.01）.（4） The influence of LDR⁶⁰Co γ ray radiation on immunologic systemThymus index and spleen index decrease after14d and28d exposure （P<0.05or P<0.01）. ConA-induced lymphocyte transformation rate decrease after exposure（P<0.01） （5） The influence of LDR⁶⁰Co γ ray radiation on genital systemEpididymis index decrease after45d exposure （P<0.01）, testicular indexdecrease after exposure after14d and45d exposure （P<0.05）, sperm relative countdecrease in radition groups than in those of blank control after14d and45dexposure （P<0.05）.（6） The influence of LDR⁶⁰Co γ ray radiation on antioxidant systemCompare with the blank control group, SOD content of irradiaton groupsshowed a decreasing trend（P＞0.05）, However, MDA activity increase after28dand45d exposure （P<0.01）.（7） The influence of LDR⁶⁰Co γ ray radiation on lipid metabolismSerum TC decrease after45d exposure （P<0.05）. TG levels of irradiated ratsdecrease after28d and45d exposure （P<0.05）, RT-PCR assay found that theexpressions of CYP7A1were significantlyly decreased.in⁶⁰Co γ ray radiationgroups, the expressions of irradiation groups were0.396times,0.228times and0.140times than those of the blank chontrol group. Differences were’t detected inthe expressions of PPARα and FABP1.3. Effects of low-dose rate co-irradiation exposure（1） The influence of LDR co-irradiation on body weight.Body weight significantly decrease after exposure （P<0.05or P<0.01）.（2） The influence of LDR⁶⁰Co γ ray radiation on digestive systemIntestinal length decrease after14d and28d exposure （P<0.05or P<0.01）,increase after45d exposure （P<0.05）, LPS content significantlyly increase after45d exposure （P<0.01）, liver index significantly increase after exposure （P<0.05orP<0.01）.（3） The influence of LDR⁶⁰Co γ ray radiation on hematological systemBone marrow DNA content OD values of radiation groups significantlydecrease （P<0.05or P<0.01）. Compare with the blank control, WBC, RBC and PLTwere decreased in radition groups after exposure （P<0.01）.（4） The influence of LDR⁶⁰Co γ ray radiation on immunologic systemThymus index and spleen index decrease after exposure （P<0.05or P<0.01）.ConA-induced lymphocyte transformation rate decrease after exposure （P<0.01）（5） The influence of LDR⁶⁰Co γ ray radiation on genital systemTesticular index decrease after28d and45d exposure （P<0.05or P<0.01）, epididymis index decrease after exposure （P<0.01）, sperm relative count decrease inradition groups than in those of blank control after exposure （P<0.05or P<0.01）.（6） The influence of LDR⁶⁰Co γ ray radiation on antioxidant systemCompare with the blank control group, SOD content of irradiaton groupsdecrease after exposure （P<0.05or P<0.01）.However, MDA activity increase（P<0.01）.（7） The influence of LDR⁶⁰Co γ ray radiation on lipid metabolismRT-PCR assay found that the expressions of CYP7A1were significantlylydecreased.in⁶⁰Co γ ray radiation groups, the expressions of irradiation groups were0.300times,0.181times and0.128times than those of the blank chontrol group.Differences were’t detected in the expressions of PPARα and FABP1.【Conclusions】This study indicates that single and co-irradaiation LDR induced injuries in gastrointestinal system, bone marrow and hematological system, immunologic system, genitalsystem, Antioxidant system. As time increases, the cumulative dose increases, radiationtypes increases, the injury increases. The results inhibiting that LDR affect lipidmetabolism in cholesterol metabolism pathway.