Studies Of Rats' Auditory Changes Caused By Lead, Cadmium, Chromium And Mercury And The Contradict Effects Of Copper, Manganese, Zinc And Selenium

ObjectiveTo evaluate effects on auditory changes caused by heavy metal lead,cadmium, chromium or mercury and the contradict effects of zinc,selenium,copper and manganese.Lead,cadmium,chromium and mercury are common pollutants in nature and they could cause variety toxicities and damage hearing functions after entering organism.Zinc,selenium,copper and manganese are essential microelements,excess intake of lead,cadmium,chromium or mercury ions would influence the level of zinc, selenium,copper or manganese ions in organism;otherwise the appropriate amount of zinc,selenium,copper or manganese could enhance the excretions of lead,cadmium, chromium or mercury to relieve toxicities of them.The aim of this study is to study the effects of lead,cadmium,chromium or mercury on rats hearing system and the contradict effects of zinc,selenium,copper or manganese on them;at the same time, we also approached the probable mechanisms of toxicities of lead,cadmium, chromium or mercury and contradict effects of zinc,selenium,copper or manganese. Results show that zinc,selenium,copper or manganese could relieve hearing injuries caused by lead,cadmium,chromium or mercury.Methods1.ANIMAL TREATMENT170 Wistar rats weighing 140-270g,85 female and male separately,were divided randomly into 34 groups and were administered different drugs through intragastric administration according to different groups and dosages,and the changes of rats in physical sign,behavior and weight were observed.1.1 Control groups:5 male and 5 female rats in these groups were feed with common feedstuff and saline water.1.2 Lead-exposed groups:5 male and 5 female rats in these groups were subjected to 4mg/kg lead acetate through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.3 Copper protective groups(lead-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg copper sulfate and 4mg/kg lead acetate through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.4 Manganese protective groups(lead-exposed):5 male and 5 female rats in these groups were subjected to 4mg/kg lead acetate and 2mg/kg manganese sulfate through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.5 Cadmium-exposed groups:5 male and 5 female rats in these groups were subjected to 4mg/kg cadmium chloride through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.6 Copper protective groups(cadmium-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg copper sulfate and 4mg/kg cadmium chloride through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.7 Manganese protective groups(cadmium-exposed):5 male and 5 female rats in these groups Were subjected to 2mg/kg manganese sulfate and 4mg/kg cadmium chloride for 30 days,and feed with common feedstuff and deionized water.1.8 Chromium-exposed groups:5 male and 5 female rats in these groups were subjected to 4mg/kg potassium dichromate through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.9 Copper protective groups(chromium-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg copper sulfate and 4mg/kg potassium dichromate through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.10 Manganese protective groups(chromium-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg manganese sulfate and 4mg/kg potassium dichromate for 30 days,and feed with common feedstuff and deionized water.1.11 Zinc protective groups(chromium-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg zinc sulfate and 4mg/kg potassium dichromate through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.12 Selenium protective groups(chromium-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg sodium selenite and 4mg/kg potassium dichromate for 30 days,and feed with common feedstuff and deionized water.1.13 Mercury-exposed groups:5 male and 5 female rats in these groups were subjected to 4mg/kg mercury bichloride through intragastric administration for 30 days, and feed with common feedstuff and deionized water.1.14 Copper protective groups(mercury-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg copper sulfate and 4mg/kg mercury bichloride through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.15 Manganese protective groups(mercury-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg manganese sulfate and 4mg/kg mercury bichloride for 30 days,and feed with common feedstuff and deionized water.1.16 Zinc protective groups(mercury-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg zinc sulfate and 4mg/kg mercury bichloride through intragastric administration for 30 days,and feed with common feedstuff and deionized water.1.17 Selenium protective groups(mercury-exposed):5 male and 5 female rats in these groups were subjected to 2mg/kg sodium selenite and 4mg/kg mercury bichloride for 30 days,and feed with common feedstuff and deionized water.2.Measurement of auditory brainstem response(ABR)ABR and the latency of waveâ… were measured.Each group of rats was anesthetized by pentobarbital sodium,ABR and the latency of waveâ… of 90db and 60db stimuli were recorded by inserting ground electrode into temporal apophysis, recording electrode into cupular part of head and reference electrode into the ear.Results1.ABR figures and waveforms of control groups were normal and clear,the latencies of waveâ… were short,showing that the hearing functions is normal in rats.2.ABR figures and waveforms of lead-exposed groups were hard to identify, further more,the latencies of waveâ… were prolonged than that of control groups, showing that lead exposing caused serious hearing loses in rats.3.ABR figures and waveforms of copper protective(lead-exposed)groups were relatively clear,the latencies of waveâ… were approximately the same to that of normal latency,showing that the hearing functions were partly recovered in rats of copper protective groups to that of lead-exposed groups.4.ABR figures and waveforms of manganese protective(lead-exposed)groups were relatively clear,the latencies of waveâ… were approximately the same to that of normal latency,showing that the hearing functions were partly recovered in rats of manganese protective groups to that of lead-exposed groups.5.ABR figures and waveforms of cadmium-exposed groups were merely identified,and the latencies of waveâ… were prolonged than that of control groups. Results show that hearing functions in this group were seriously damaged by cadmium.6.ABR figures and waveforms of copper protective(cadmium-exposed)groups were relatively clear,the latencies of waveâ… were approximately the same to that of normal latency which show that copper has protective effects on damages of hearing functions caused by cadmium.7.ABR figures and waveforms were also relatively normal in manganese protective groups(cadmium-exposed)and the latencies of waveâ… were approximately the same to that of normal latency.Results show that manganese has protective effects on damages of hearing functions caused by cadmium.8.ABR figures and waveforms were merely identified in chromium-exposed groups,and the latencies of waveâ… was prolonged than that of control groups. Results show that hearing functions in this group were seriously damaged by chromium.9.ABR figures and waveforms were relatively normal in copper protective groups (chromium-exposed)and the latencies of waveâ… were approximately the same to that of normal latency which show that copper has protective effects on damages of hearing functions caused by chromium.10.ABR figures and waveforms were also relatively normal in manganese protective groups(chromium-exposed)and the latencies of waveâ… were approximately the same to that of normal latency.Results show that manganese has protective effects on damages of hearing functions caused by chromium.11.ABR figures and waveforms were relatively normal in zinc protective groups (chromium-exposed)and the latencies of waveâ… were approximately the same to that of normal latency which show that zinc has protective effects on damages of hearing functions caused by chromium.12.ABR figures and waveforms were also relatively normal in selenium protective groups(chromium-exposed)and the latencies of waveâ… were approximately the same to that of normal latency.Results show that selenium has protective effects on damages of hearing functions caused by chromium.13.ABR figures and waveforms were merely identified in mercury-exposed groups, and the latencies of waveâ… were prolonged than that of control groups.Results show that hearing functions in this group were seriously damaged by mercury.14.ABR figures and waveforms were relatively normal in copper protective groups (mercury-exposed)and the latencies of waveâ… were approximately the same to that of normal latency which show that copper has protective effects on damages of hearing functions caused by mercury.15.ABR figures and waveforms were also relatively normal in manganese protective groups(mercury-exposed)and the latencies of waveâ… were approximately the same to that of normal latency.Results show that manganese has protective effects on damages of hearing functions caused by mercury.16.ABR figures and waveforms were relatively normal in zinc protective groups (mercury-exposed)and the latencies of waveâ… were approximately the same to that of normal latency which show that zinc has protective effects on damages of hearing functions caused by mercury.17.ABR figures and waveforms were also relatively normal in selenium protective groups(mercury-exposed)and the latencies of waveâ… were approximately the same to that of normal latency.Results show that selenium has protective effects on damages of hearing functions caused by mercury.ConclusionsHearing functions of rats could be partly damaged by been exposed to lead, cadmium,chromium and mercury,and zinc,selenium,copper and manganese showed some protective effects on the damages caused by them,hint that zinc, selenium,copper or manganese has some contradict effects to the toxicities of lead, cadmium,chromium or mercury to the hearing losses in rats,and partly relieve the impairment to hearing functions caused by them.