| Backgrounds:Cd is a high toxic and widespread heavy metal pollutant in the environment.The problem of cadmium pollution has caused people's high attention,and people's research on the potential damage of cadmium is also increasingly in depth.At present,the research on cadmium in the world mainly focuses on cadmium pollution and its hazards,and the main research object is total cadmium,but there are few studies on the absorption and utilization of cadmium binding proteins.With the serious cadmium pollution in the environment increasingly,the problem of rice cadmium pollution in China is exposed gradually.More than 60% of the country's population is based on rice as a staple food.Usually,cadmium in rice is mainly combined with proteins,But in many countries,the assessment of dietary exposure of cadmium in populations is based on the level of cadmium contamination in foods and ignored the body's exposure,so overestimated the body's exposure to cadmium.Therefore,this project intends to use in vivo experiments to detect and analyze the distribution of cadmium in tissues and organs about animals,then analyze and compare with their differences of absorption and distribution and bioavailability between cadmium-bound gluten in rice and inorganic cadmium in vivo.This will provide a more scientific basis for the determination of cadmium limit standard in rice.Methods:1)Using the method of Osborne to extract rice albumin,globulin,glutenin,and gliadin in rice,and determine the protein content and cadmium content of these four proteins in rice.2)Using 63 female Kunming mice for animal experiments,according to their body weight,they are randomly divided into 3 groups(solvent control group,cadmium chloride group and cadmium binding gluten group),21 in each group.The same molecular quality of cadmium was used to gavage.The control group is lavaged with the same amount of ultrapure water.The physiological activity was observed.After the end of the experiment,euthanasia is performed and collected their blood and organs;3)Using the kit to measure the content of ALT,AST,?-GT,BUN,CR,TC,TG and GLU of mice plasma,and test the activity(or content)of CAT,T-SOD,GSH-PX and MDA in the liver and kidney tissues.Various organ tissues of mice were stained with HE and observed with an optical microscope.4)MD-ICP-MS was used to determine the content of cadmium in tissues of mice and the distribution of cadmium in blood at different time points.The in vivo bioavailability of different forms of cadmium was analyzed and compared.Results:1)Extraction of cadmium binding gluten in riceThe method of Osborne is used to extract Cd-binding protein in rice.The relative percentage order of the four protein contents in rice are gluten> gliadin> globulin >albumin;After determination of cadmium content in four rice proteins,the results showed that gluten(3.130 ± 0.143 mg/kg)> albumin(0.825 ± 0.023 ug/kg)> gliadin(0.278 ± 0.008 ug/kg)> globulin(0.239 ± 0.071 ug/kg),combing with the rate of each protein's extraction,it can be seen that cadmium mainly bind with glutenin in rice.2)Effect of physiological and biochemical indexes of Kunming mice by cadmium binding glutenin in riceIn the inorganic cadmium chloride(cadmium chloride)group and the cadmium combined glutenin experimental group,the body weight gain of the mice about two groups are slight lower than those of the control group after 21 days,but there was no significant difference;After 3 weeks of cadmium exposure,the visceral index of the heart,spleen and liver in the mice of the cadmium chloride group increased significantly(P<0.05).The visceral index of the kidney in the mice of the cadmium binding glutenin group was significantly higher than that of the control group(P<0.05).Compared with the cadmium chloride experimental group and the cadmium chloride group,there was no significant difference in the organ coefficient between the two groups of experimental mice(P>0.05).It is found through the naked eye and pathology that there was some degree of damage in the livers of both the cadmium chloride group and the cadmium-associated glutenin experimental group after the cadmium exposure of 3 weeks.After two weeks of continuous exposure to cadmium,the content of AST in the plasma of cadmium chloride group was significantly lower than that of the control group(P<0.05),while the content of AST in the plasma of the mice was significantly higher than that of the cadmium chloride group(P<0.05).After two and three weeks of continuous exposure to cadmium,the content of CR in the plasma of cadmium binding glutenin experimental group was significantly higher than that in the cadmium chloride group(P<0.05),It was shown that the cadmium-bound glutenin in rice had a significant degree of change in liver and kidney function in mice than cadmium chloride.According to the analysis of oxidative damage indexes of liver and kidney tissues in experimental mice,CAT activity and T-SOD activity in liver tissue of cadmium chloride mice were significantly lower than that of cadmium binding gluten group after three weeks of continuous exposure to cadmium(P< 0.01),while cadmium chloride mouse kidney CAT activity and GSH-Px activity were significantly lower than the cadmium binding gluten group(P <0.01),cadmium chloride mouse kidney tissue activity was significantly higher than cadmium binding Valley Protein group(P<0.01).The results showed that with the increase of exposure time,the activities of antioxidant enzymes CAT,GSH-Px,and T-SOD were inhibited to varying degrees in liver tissue and kidney tissue of mice in the cadmium-binding gluten group and the cadmium chloride group.The content of MDA in the cadmium chloride group was increased.Compared with the cadmium-associated gluten group,the oxidation of liver tissue and kidney tissue was more obvious in the cadmium chloride group.3)Bioavailability of cadmium-binding proteins in rice in vivo testThe microwave-digested inductively coupled plasma mass spectrometry was used to detect and analyze the cadmium content in tissues and blood of mice in experimental groups.The in vivo absorption and distribution of cadmium-binding gluten and inorganic cadmium in rice were analyzed and compared.The experimental results showed that in the cadmium chloride group and the cadmium-associated glutenin experimental group,the blood cadmium content was significantly higher than that in the control group at 0.5h(P<0.05),and the peak content of cadmium in the blood of the two groups was 2h and 8h.The cadmium in the cadmium chloride group of experimental animals could be detected in the blood samples of the rats within 48 hours,while the cadmium combined gluten group animals were lower than the LOQ in 32 hours.The results showed that cadmium combined gluten is more rapidly metabolized in the blood than cadmium chloride.Cadmium binding glutenin and cadmium chloride are used to poisonse mice respectively,the absorption distribution in the target organ of mice was mainly concentrated in the kidney and liver,and the cadmium in the liver is higher than that of the kidney.After a week of cadmium exposure,cadmium accumulation in cadmium chloride group and cadmium combined glutenin group were significantly higher than that of the control group(P<0.01),but the accumulation rate of cadmium in the cadmium chloride group was not significantly different from that of the cadmium binding glutenin group.After cadmium exposure for two weeks and three weeks,the accumulation rate of cadmium in cadmium binding glutenin group was significantly lower than that in cadmium chloride group(P<0.01).The results showed that cadmium binding glutenin in rice is not easy to accumulate compared with inorganic cadmium in vivo.ResultsThe short-term low-dose rice Cd-associated gluten and cadmium chloride were administered separately to healthy Kunming mice.The Cd-binding glutenin in rice had a slightly greater change in liver and kidney function than that in cadmium chloride;the cadmium chloride group was small.The degree of oxidation in the liver and kidney of rats was significantly greater than that in the cadmium-associated gluten group;cadmium-bound gluten was more rapidly metabolized in the blood than cadmium chloride;Cadmium-associated gluten in rice was less likely to accumulate in the body than cadmium chloride. |
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