| Lead is ubiquitously a kind of heavy metal that was regarded as one of the three mostnoxious metals, so it is widespread paid attention. Lead can be determined during any partof environmental and ecological system with the fast development of modem industry.Lead was widespread used, especially in the recent two decades, the quantity exceeded thatof the all past years that lead to the local and global pollution of the air, smoking and soil.Lead is a huge harmful kind of heavy metal for the body that can lead to the dysfunction onthe nerve system, hematogenic system, digestive system and reproductive system, etc. Wecan find many studies of the lead toxicology on the mammal of human and rat, meantime,the research on bird were mainly focused on wild kinds. Few data was found out about thelead deposition and the effect of lead on the embryo toxicology of chick in the way offeedstuff. In the paper, the lead was added in the way of feedstuff and the experimentalanimal was the poultry chicks that were feed on a large scale. The lead deposition ofhatching eggs and the tissue and organ of the chick embryos was researched in order tounderstand the organ specificity of lead deposition. With the help of histopathology and cellultrastructure, we realized the effect of lead on the hepatic and renal cell structure; in thesame time, we discussed the change of antioxidant enzymes of liver and kidney in order tounderstand the lead toxicity mechanism for chick embryos, which provided a theory basisabout the further research of lead toxicology.The contents and results were as follows.1. The deposition of heavy metals in fresh eggs In this paper, the chick eggs saled in NanJing City JiangSu Province were randomlysampled to examine the deposition of heavy metals according as the national harmlessstandards, the results was showed that the deposition of heavy metals in chick eggs fromdifferent places and breeds varied. The content of lead in all eggs (egg white, egg yolk andwhole egg) except for harmless eggs unlimitedly exceeded that of the standard. The contentof lead in egg white, egg yolk and whole egg was 0.2054～0.5817mg·kg-1, 0.3788～1.2918mg·kg-1, 0.3365～0.8787mg·kg-1, respectively. The deposition in egg yolk was maxim. So,the super-concentration of lead in fresh eggs and relative resolvent should be paid attention.2. The deposition and effect of different contents of lead in feedstuffon the hatching eggsThe lead of different contents were added into the laying chick (ISA) feedstuff toresearch the deposition in hatching eggs and the effect of lead on the quality of eggs. Theexperiment was divided into four groups as follows: ck group, adding lead of 15mg·kg-1group, 30 mg·kg-1 group, 60 mg·kg-1 group. The duration of whole experiment was 30 days.Content of components in hatching eggs was determined in the 0, 5th, 10th, 15th, 20th, 25th,30th day, respectively. The results were showed that the deposition of lead in components ofhatching eggs and the quality of eggs was influenced by the adding lead into feedstuff anddeposition period. In the short period, lead did not influence the egg weight; the eggshape index was affected without order according to the lead residue level which could leadto the malformation of the eggs and harm the development of embryo. For all componentsof eggs, lead was mainly deposited into eggshell, then egg yolk, all of which weresignificantly higher than that of egg white and whole eggs. The deposition of eggshell madethe shell thin, but the eggshell strength was not influenced and the percentage of crackedeggs significantly dropped.In the 25th day of the experiment period, the deposition of components was up to themaximum. At the same time, the correlation coefficient between the content of eggshell andwhole egg was to remarkable level, 0.857. The stepwise regression equation wasy=1.845*10-2a+0.265 (y indicated lead content in whole egg, a indicated lead content ineggshell), which gave a clue of that lead content in eggshell could be examined to forecastthat in whole eggs. When the content in feedstuff was lower 15 mg·kg-1, the deposition ineggs was not significantly different compared with ck group. The 25th hatching eggs wereselected as the sampling period in the later experiment. 3. The deposition and effect of different content of lead in feedstuffon tissue and organs of chick embryo at different growing periodThe hatching eggs in the 25th day were hatched. At the 9th, 14th,19th day of hatchingperiod, tissue and organs of chick embryos were gained to determine the content of lead inorder to discuss the effect of deposition of lead on chick embryo. The results were showedthat the period of maximum deposition was the 14th chick embryos. At this time, the orderof content in tissue and organs was kidney, liver, the lowest muscle. The content of lead inmuscle in every group was lower than that regulated in national standard. When the contentof lead in feedstuff was up to 30mg·kg-1, the deposition in embryos was maximum; at thistime, for the 14th chick embryos, the content of kidney, liver and muscle was up to1.2193mg·kg-1, 0.2714mg·kg-1, 0.1446mg·kg-1, respectively. The correlative coefficientsbetween content of lead in feedstuff and that of kidney of the 14th and 19th embryos werestatistically significant, 0.574 and 0.380.4 The effect of the different content of lead in feedstuff onhistopathology and ultrastructure of liver and kidney of chick embryos atdifferent growing periodThe combinative analyse of histopathology and the deposition status of heavy metalscould provide the most valuable information on the effect of heavy metals on the organismtissue. In this paper, the observation on the histopathology and ultrastructure of liver andkidney of chick embryos at different growing period was carded out to discuss the effect oflead on the histopathology of chick embryos. The results were showed that lead did notsignificantly influence the histopathology of liver. In the 9th day of chick embryos, the kindsand quantity of organelle of liver were fewer than that in the 14th and 19th day. Meantime,the kinds and quantity of organelle of kidney were more than that of liver.For the liver of the 14th and 19th day of embryos, lead of 15mg·kg-1 in feedstuff couldlead to the slight pathological changes of hepatic cells, and when the content of lead was upto 30mg·kg-1, the pathological changes of liver was obvious. The subcellular structure ofliver was most sensitive to lead. For the kidney, the content of 15mg·kg-1 of the lead infeedstuff could find the obvious pathological changes in renal tissue and organelle, so, theeffect of lead on kidney was significantly higher than that on liver. We also found that30mg·kg-1 and 60mg·kg-1 of lead destroyed the two organs to the same extent, which showedthat 30mg·kg-1 of lead was the maximum of damaging the liver and kidney. The histopathological changes of hepatic and renal cells were represented in the way oftransmutation of cells, the largement of cell interspace, the swollen karyotheca andmitochondrion, unclearness, breakage and dissolution of inner cristae, and the production ofinflammation.5. The effect of the different content of lead in feedstuff on thehepatic and renal antioxidant capacity of chicken embryos at differentgrowing periodThe hepatic and renal antioxidant enzyme activities of chick embryos were determinedto discuss the toxicology mechanism of lead on chick embryo. The results were showed thatwith the development of chick embryos, the hepatic and renal MDA content decreased;hepatic SOD and GST activities dropped; CAT and GR activities increased. But all of renalantioxidant enzymes fell with the development of chick embryos. For the 9th day chickembryos, hepatic GST activity decreased with the adding of lead; all of antioxidantenzymes activities except for descendent CAT activity did not change for the 14th day chickembryos. Only for the 19th day chick embryos, all antioxidant enzymes decreased with theadding of lead in the feedstuff. The above results were showed that the effect of lead on thehepatic antioxidant capacity did not obvious, but lead decreased the renal antioxidantcapacity with the development of chick embryos. Lipoxidantion reaction was not a majorindicator of lead toxicology. A mechanism of lead toxicology on chick embryo was thatlead inhibited the antioxidant enzyme activities. And the results were showed that kidney isa major organ that regulated the antioxidant system of chick embryo.
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