| Background:As a new persistent inorganic pollution,perchlorate had been widely existed in our environment.It can competitively inhibit iodine absorption by the thyroid gland,there may be potential health risks to long-term human exposure.In recent years,many researchers had evaluated the risk assessment of perchlorate in daily food,but most of them were based on the total perchlorate concentration in the food,and assume that all perchlorate in foods were absorbed by the body.It was obvious that could expand the biological effective dose of perchlorate in foods,and affect the accuracy of risk assessment.The release levels of perchlorate in different food matrices in the body were not the same.Therefore,it was important to investigate the bioavailability of perchlorate in different food matrices.Method:(1)In order to make the perchlorate concentration in food matric met the experimental requirements,the perchlorate was added manually,among which rice and milk powder were added to three different concentrations: H(10mg/kg),M(1mg/kg)and L(0.5mg/kg).Soybean and meat were added to the same concentration(10mg/kg),and the nutritional composition of food matrix before and after the addition was analyzed.The in vitro gastrointestinal digestion model was used to optimize the digestion conditions of meat and explore the bioaccessibility of perchlorate in different food matrix under optimal conditions.(2)Building the Caco-2 single cell membrane model,and measuring its cross epithelial resistance(TEER)value,AKP and the permeability of monolayer cell membrane to fluorescein sodium to evaluate the tightness,polarity and permeability of the model.After the three stages of in vitro digestion,the in vitro bioavailability of perchlorate was studied by transport and absorption experiments using cell model.(3)After adaptive feeding for one week,72 male ICR mice were randomly divided into 12 groups(fodder,fodder + perchlorate,rice + fodder + perchlorate,rice + fodder,milk powder + fodder + perchlorate,milk powder + fodder,lettuce + fodder + perchlorate,lettuce + fodder,soybean + fodder + perchlorate,soybean + fodder,meat + fodder + perchlorate,meat + fodder),and each mice was raised separately in a metabolic cage.The bioavailability of perchlorate in mice was calculated by measuring the accumulation of perchlorate in each tissue after feeding the artificial mixed fedder for one week.Result:1.Bioaccessibility of perchlorate in different food matrixesThe optimal conditions for the p H,volume and digestion time of the meat in the oral digestion phase were 7.4,5min and 7ml respectively.The optimal condition for gastric digestion were 3,2.5h and 10 ml respectively.The optimal condition for intestinal digestion were 7.5,3h and 10+5ml respectively.The bioaccessibility of different food matrixes under optimal conditions are as follows: rice-L(73.02±10.04%),rice-M(88.38±23.45%),rice-H(70.95±1.13%),milk powder-L(60.53±5.57%),milk powder-M(74.19±1.35%),milk powder-H(73.19±3.32%),soybean(81.83±0.70%)and perchlorate control(93.44±7.61%).2.In vitro bioavailability of perchlorate in different food matrixesIn the cell model,the absorbance of perchlorate in rice-L,rice-M and rice-H were 31.94±3.76%,21.17±14.70% and 22.19±6.32% respectively.The milk powder-L,milk powder-M and milk powder-H were 27.50±2.35%,40.22±4.46% and 27.16±0.91% respectively.At the same concentration level,the absorption rates of rice,milk powder,soybean,meat and perchlorate control were 22.19±6.32%,27.16±0.91%,35.68±5.48%,24.28±2.77% and 25.79±2.94% respectively.The in vitro bioavailability of perchlorate in rice-L,rice-M and rice-H were 6.34±0.84%,9.04±6.83% and 8.41±3.78% respectively.The milk powder-L,milk powder-M and milk powder-H were 10.67±2.21%,23.81±0.43% and 10.79±0.44% respectively.At the same concentration level,the in vitro bioavailability of perchlorate in rice,milk powder,soybean,meat and perchlorate control were 8.41±3.78%,10.79±0.91%,9.73±1.05%,12.15±2.62% and 15.56±3.74% respectively.3.In vivo bioavailability of perchlorate in different food matrixesThe distribution of perchlorate in mice was as follows: The highest concentrations of perchlorate were found in the thyroid and brain of all experimental groups,followed by the spleen.In milk powder + fodder + perchlorate and rice + fodder + perchlorate groups,the distribution of perchlorate was: brain > thyroid > spleen > lung > heart,followed by liver and kidney.In soybean + fodder + perchlorate and fodder + perchlorate groups,brain > thyroid > spleen> heart > lung,followed by liver and kidney.Compared with the ‘non-added’(do not add perchlorate)groups,the accumulate rate of the ‘added’(add perchlorate)groups was significantly reduced.Most of the perchlorates were eliminated by urine and feces,only a few accumulated in the body.In ‘non-added’(do not add perchlorate)groups,the bioavailability of perchlorate in mice was as follows: rice + fodder(80.44±3.63%),meat +fodder(76.54±1.91%),milk powder + fodder(73.05±2.49%),fodder(72.25±4.80%),lettuce + fodder(62.76±2.03%)and soybean + fodder(61.80±9.31%).In ‘added’(add perchlorate)groups,the bioavailability of perchlorate in mice was as follows: lettuce + fodder(45.60±7.11%),meat +fodder(37.05±5.14%),fodder(35.76±2.88%),rice + fodder(32.93±7.94%),milk powder + fodder(20.27±9.39%)and soybean + fodder(18.01±4.53%).Conclusion:In rice and milk powder,the in vitro bioavailability of perchlorate increased and then decreased by the concentration.Different food matrixes also affect the bioavailability of perchlorate in vivo and vitro.The ‘non-added’(do not add perchlorate)groups contained a small amount of perchlorate,Compared with those groups,the accumulation rate of perchlorate in mice was significantly reduced in ‘added’(add perchlorate)groups(P<0.05),and the excretion rate in feces and urine was significantly increased(P<0.05),which was similar to the bioavailability in vitro. |
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