Studies Of In Vitro Digestion And Absorption Of Cadmium In Contaminated Rice

China is the country with the biggest rice production and consumption,about more than 60%Chinese make rice as the staple food,with the increase of China's farmland and water pollution,China's rice cadmium(Cd)pollution situation is grim.Cadmium is known as one of the most easily accumulated toxic substances in the body,and low dose of cadmium exposure can lead to cancer and the occurrence of many chronic diseases.Therefore,it is of great practical significance to study the digestion and absorption of Cd in rice,and to evaluate the risk of cadmium exposure and to carry out effective dietary intervention.This paper used the Caco-2/HT-29 cells(70:30)rapidly co-cultured intestinal absorption model coupled with RIVM method for in vitro digestion,simulation of human oral,gastrointestinal digestion and intestinal absorption,the aim is to research the Cd bioavailability and bioaccessibility of rice in vitro and analyze the changes relationship between Ca,Fe,Cu,Zn,and Cd,also analyze whether EGCG decrease Cd uptake or not,finally conduct the risk assessment of rice.The main results are as follows:The experiment were conducted to establish the Caco-2/HT-29(70:30)cell co-culture with differentiation agent butyric acid.The two kinds of cells were co-cultured with different ratio(100:0,90:10,80:20,70:30,60:40,50:50),and then two type of rapid differentiation agent(butyric acid,ascorbic acid)were added in culture mediea in model.The transepithelial electrical resistance value,alkaline phosphatase activity(AP/BL),fluorescence permeability coefficients and morphological observation were measured,These results indicated that the rapidly co-culture Caco-2/HT-29(70:30)intestinal absorption model with adding butyric acid as differentiation agent had similarity to the standed culture intestinal cells model in morphology,polarity,and tight junctions.The bioavailability of three kinds of rice with the same intake,in gastric phase were greater than in small intestinal phase.The bioavailability of gastric phase values were from 59.04%to 80.23%,average value is was 69.79%;in small intestinal phase values were from 37.14%to 52.93%,average value was 42.58%.In gastric phase:Rice C 80.23%>Rice A 70.11%>Rice B 59.04%.At the end of gastric digestion phase 7 h:Rice A(52.63%),Rice B(48.19%)and Rice C(39.68%).The bioavailability of the same kind of rice with different feeding in gastric digestion phase were greater than in small intestinal phase,and the bioavailability of small intestinal phase decreased with the increase of cooked rice intake.The bioavailability of gastric digestion phase:20g Rice B 88.19%>30g Rice B 80.84%>10g Rice B 59.04%,10g Rice C 80.23%>20g Rice C 77.29%>30g Rice C 62.08%.The bioavailability of small intestinal phase 7 h:lOg Rice B 48.43%>20g Rice B 32.15%>30g Rice B 21.74%,lOg Rice C 39.68%>20g Rice C 25.03%>30g Rice C 19.63%.There are some interaction between the elements in the supernatant of digestive jucie.From gastric digestion phase 2 h to small intestinal phase 0.5 h,the mass concentration of Cu decreased suddenly,the mass concentration of Ca,Fe and with the corresponding Cd bioavailability showed increasing trend,while the mass concentration of Zn and the Cd bioavailability also showed a downward trend.In the whole small intestinal phase 7 h,the mass concentration changes of Ca and Fe in the supernatant of digestion were similar,but the variation range of Fe larger;Cu may be more easily dissolved in the rice digestion juice,the Cd bioavailability and Zn mass concentrationin were the same trend.The absorption rates of Ca,Fe,Zn,Cu,Cd in absorption experiment of cell model were very different,the absorption rate of Cd was for a certain degree of inhibition with adding the two concentration of EGCG groups in the rice digestive juice.The uptake rates of Fe and Cd,Cu,and Cd showed a consistent pattern of the 3 groups.The uptake rates of Fe and Cu gradually increased,and the uptake rate of Cd gradually decreased.The Cd uptake ratc:10g Rice C digestive juice group values was 37.04%,adding 21.85 ?mol/L EGCG group values was 31.48%,and adding 43.70 ?mol/L EGCG group values was 23.15%.The cooking process have some effect on the bioaccessibility of Rice C(high Cd level).The bioaccessibility of Rice C(29.13%)and Cooked Rice C(29.74%)in the whole digestive and absorption phase have smaller difference.In the same group,the differences values were 0.61%?0.74%,with adding 21.85 ?mol/L EGCG,Rice C decreased by 0.93%,Cooked Rice C decreased by 2.33%;with adding 43.70 ?mol/L EGCG,Rice C decreased by 0.88%,Cooked Rice C decreased by 1.27%.Risk exposure assessment shows that the maximum daily Cd exposure of Rice C,Rice B,Rice A are 2.544 ?g,1.711 ?g,0.374 ?g,respectively,among them,Rice C are 3.08 times and Rice B are 2.06 times as long as the daily tolerable exposure;The daily maximum Cd absorption amount of the three rice are 101.337 ?g,82.443 ?g,20.801 ?g,respectively.