The Mechanism And Effect Of Long-term Exposure To The Lanthanum Chloride On The Centre Neural System

ObjectiveWith the increasingly widespread application of rare earth in our country, especially being added to fertilizer and feedstuff for agriculture and livestock farming. A growing number of rare earth elements have appeared in our environment , and entered into our food - chain. More and more people pay close attention to the effect of the rare earth exposure on the environment and physical health. A lot of researches have shown that the rare earth wont induce gene mutation , deformities or tumour genesis. Low dose rare earth exposure can enhance the function of the immune system and the ability of anti - oxidation . But according the epidemiology investigation result coming from weifang Zhu , the function of the central nervous system among populations in a rare earth element area decrease. Experiments in vitro or acute toxicity have also shown that the rare earth elements inhibit the release of neurotransmitter and interfere with the transmission of signals. There havent any reports on the chronic toxicity of the rare earth elements yet. In this study, we added light rare earth element lanthanum to the drinking water of the rats and detected the concentrations of some macro - and trace elements in rat brains using NAA;Observed the change of the rats'ability of learning and memory ,analysised it with the concentrations of Ach , the protein and the activity of the Ach E , Ca²⁺ - ATPase in hippocampus;We want to investigate the influence of different dose exposure to rare earth lanthanum on the physical - or neurodevelopment of the offsprings.Method1 The effect of long - term intake of lanthanum chloride on the concentra-tions of some macro - and trace elements in rat brains using NAA .60 male Wistar rats, 134. 3 ± 13.4g of weight, were purchased from Laboratory Animal Center in China Medical University. The animals were housed at 17 -23Ti. The rats were given unlimited access to drinking water, to which we added 0, 0.04, 0.4 , 4 mmol light rare earth lanthanum chloride individually and rat chow which was provided by Laboratory Animal Center. The animals were fed for seven days before experiment. They were divided into four groups randomly: the control group, low dose group , middle dose group and high dose group, each group have 15 male. After 6 months exposure to lanthanum, we collected the brain tissues under the ether anesthesia and weighted it over the ice. The brain was separate into 2 parts, one was used for determination of biochemical indexes, the other was used to determination of trace elements. After Cryodesiccating, comminuting, misce bening ,we weighted 100 mg of it as the samples, sealing up it with polythene for short — term irradiation or sealing up it with two layers of lens papers and pure aluminium foil for long - term irradiation. The samples were sent to Chinese atomic energy institute for irradation.2 The effect of long term exposure to lanthanum chloride on the ability of learning and memory of adult rats.The methods of grouping animals and exposure to lanthanum are the same as part one . After six months exposure to lanthanum of different dosage among four groups. Then Y - maze was used to measure the rats'ability of learning and memory. After the test, the rats were killed. The concentration of the protein in brains was determined by Lowry method;the concentration of acetylcholine ( Ach) and the activities of the acetylcholinesterase ( AchE) were determined by alky hydroxylamine colourimetry;The activity of Ca2+ - ATPase was determined by measuring the generating rate of inorganic phosphours ion.3 The effect of long term exposure to lanthanum chloride on the physical and neural development of the offsrings.The methods of grouping animals and exposure to lanthanum are the same as part one. After one month , put the male of the control group and the female rats together to mate until the female was confirmed conception. We observed the indexes of the conception rate, the survival rate of the offsprings , the weight ofnewborns, the gain weight of the offsprings , pinna of ear separating rate at 3 day , the fore - tooth emerging rate at 11 day , eyes opening rate at 17day , crawling rate at 3day , 10s righting reflexing rate at 3 day. When they were 2 -month old ,we tested the offspringss ability of study and memory, then detected the enzyme activity change.4 statistical analysisAll results were analysis by SPSS 10. 0 softwear.Results1 The effect of long - term intake of lanthanum chloride on the concentrations of some macro - and trace elements in rat brains using NAA (neutron activation analysis).The results showed that, along with the elevation of the dose of lanthanum, more and more elements were affected in experimental rat brain tissues. Compared with control group, the concentrations of two elements were significant difference in low dose group (Na ,Zn ) (P <0.05) , three elements ( Na Zn Rb ) in middle dose group (P <0. 05) , and five elements ( Na Zn Rb K Mg)were significant difference in high dose group (P <0.01) . These elements have close relations with brain function.2 The effect of long term exposure to lanthanum chloride on the ability of learning and memory of adult rats.(l)Body weight and brain weight;Compared with the contral group, the body weight increase were significant difference in the low group (P <0.05) , and there were no significant difference among other groups. So did the brain weight and the ratio of brain and body weight. (2) The Y - maze exam show the performance of the low group was better than that of other groups, the difference was significant (P <0. 05). But we received the negative results in the middle group (P <0. 05). (H)The concentration of the protein determined by Lowry was lower significant in middle group than in the contral group (P <0. 05). The activity of the acetylcholinesterase (AchE) determined by alky hydroxylamine co-lourimetry and Ca2+ - ATPase in Hippocampus determined by measuring the generating rate of inorganic phosphours ion of middle and high groups were significantly higher than those of the contral. The concentration of acetylcholine ( Ach) determined by alky hydroxylamine colourimetry of the middle group was in low significant level(P < 0. 05 ).3 The effect of long term exposure to lanthanum chloride on the physical and neural development of the offsrings.(T)The conception rate : Two female rats belong to middle dose group and high dose group respectively cannot conception obstinately, others became pregnant within 20 days. There were no significant difference among four groups (P> 0. 05 ) 0 (2)The survival rate of the offsprings: There were no difference among four groups. ( P > 0. 05 ). (J) The weight of newborns;The data show that, compared with the contral group , the low dose group had significantly high body weight(P <0. 05) The middle dose group had significantly low body weight (P<0. 01). So did the gain weight of the offsprings. (4) Pinna of ear separating rate at 3 day , the fore - tooth emerging rate at 11 day , eyes opening rate at 17 day , crawling rate at 3 day , 10s righting reflexing rate at 3 day all demonstrated that the low dose group had higer percent than those of the contral group ( P<0.01). But the middle dose group was on the opposite side (P<0.01)o ? the results received from the detection of the offsprings'ability of study and memory and the activity change of the enzyme were as same as the part two.Conclusion1 Long - term exposure to lanthanum chloride lead to the change of concentration of some macro — and trace elements in rat brains. These elements have proven to have close relations with brain function. We think that exposure to lanthanum chloride may damage the function of the brain.2 Exposure to low dose lanthanum chloride may elevate the ability of learning and memory. But if we intake more, we observe the opposite effect on brain function .3 A low dose intake within breast - feeding days will promote the offspringrats physical and neural development. But we may receive the negative result if we intake more lanthanum chloride.