Study On The Combined Toxicity Of Heavy Metal Mixture And Prevention With Chemical Antagonists

Objective: Chromium(Cr),manganese(Mn),nickel(Ni),copper(Cu),zinc(Zn),cadmium(Cd),mercury(Hg),lead(Pb)are selected in order to explore joint toxicity and bio-accumulation in various organs after long-term exposure at low level.Meanwhile,chemical antagonists are implemented to evaluate their antagonism against adverse effects induced by multi-heavy metals via in vivo experiments.This research project aims to assess toxic effects and underlying mechanisms of chronic multi-heavy metal exposure as well as provide scientific and available prevention strategies for heavy metal pollution.Methods: Male Sprague-Dawley(SD)rats were used as research subjects and 500mg/kg·bw of heavy metal mixture was given orally according to the actual intake ratio of eight heavy metals through aquatic products in residents of Ningbo area.200mg/kg·bw of epigallocatechin-3-gallate(EGCG),trisodium citrate dihydrate(TCD)and glutathione(GSH)were given respectively through intragastric administration at the same time once a week while the control group received same amount of saline.All rats were access to water and fodder ad libitum.Six months after the treatments,three rats were randomly selected respectively from the control group and the heavy metal treatment groups.100mg/kg·bw of sodium 2,3-dimercaptopropane-1-sulfonate(DMPS)was then injected intraperitoneally for three consecutive days and 24 h urine samples were collected and stored at-80℃ refrigerator.Morris water maze test was conducted to explore spatial memory and cognitive function,and then rats were anesthetized.Blood samples were obtained in test tubes through the apex of the heart for blood and biochemical analysis.After the animals were all sacrificed,organs(heart,liver,spleen,lung,kidney,brain,testicle)were collected and recorded for biopsy.Inductively coupled plasma mass spectrometer(ICP-MS)was utilized for analyzing the concentration of eight heavy metals in plasma,urine,and tissues.Results: The results indicated that chronic exposure to multi-heavy metals under this experiment condition caused a significant reduction in testicle weight and viscera coefficient and an increase in lung weight and viscera coefficient as well as the rise of red cell distribution width,serum total bilirubin,indirect bilirubin and alkaline phosphatase in rats of the Mixture group after six months treatment in a statistically significant way.Histopathological examinations demonstrated that prominent pathological changes were observed in the tissues of both liver and testicle in the Mixture group.At the dose of 200mg/kg·bw,EGCG,TCD and GSH all could reduce these toxic effects and showed a protective effect on rats against the damage induced by heavy metal mixture.ICP-MS results demonstrated in plasma,urine,heart,liver,spleen,lung,kidney,brain and testicle tissues,the contents of both mercury and cadmium in Mixture,Mix+EGCG,Mix+TCD and Mix+GSH groups were remarkably higher than those in the control group.Zinc had obvious accumulation in the liver,copper in kidney and testicle,nickel in the lung as well as mercury,cadmium,lead in the kidney while there was no significant change in the contents of Mn.EGCG,TCD and GSH could promote the excretion of mercury,cadmium,chromium,nickel and copper in different tissues but this effect of lead was poor.After DMPS treatment,the excretion of mercury,cadmium,zinc and copper in urine increased significantly,and the levels of mercury in various tissues and organs could be reduced dramatically.Conclusions: Long-term intake of eight heavy metals at this experimental dosage may exert detrimental influences on hematological parameters,reproductive system and liver function in rats.Mercury and cadmium can accumulate in various organs such as heart,liver and spleen,lung,kidney,brain and testicle while EGCG,TCD and GSH can promote the excretion of heavy metals from tissues in different degrees,indicating preventive effects on the combined toxicities induced by heavy metals.DMPS shows a significant discharge effect on heavy metals,especially on the mercury,it can promote the elimination of mercury from almost all tissues and organs.