Studies Of Auditory Changes Caused By Lead Or Cadmium And Contradict Effects Of Zinc Or Selenium

Objective: 1.To evaluated effects on auditory changes caused by heavy metal lead or cadmium and contradict effects of zinc or selenium. Lead and cadmium are common pollutants in nature which usually cause variety toxicities after entering organism. All of them could injury hearing functions. Zinc and selenium are essential microelements, excess intake of lead or cadmium ions would influence amount of zinc or selenium ions in organism;otherwise zinc or selenium could enhance excretions of lead or cadmium, relieve toxicities of them. The aim of this study is to research effects on rats hearing system caused by lead or cadmium and contradict effects of zinc or selenium;at the same time, we approach probable mechanisms of toxicities of lead and cadmium and contradict effects of zinc or selenium. Results show that zinc or selenium could relieve hearing injury caused by lead or cadmium.Methods: l.To establish animal models: The animals used in studies were administered different drugs through intragastric administration according to different groups and dosages, we observe changes of rats in physical sign, behavior and weight. (1) Lead poisoning groups: Rats in this group were subjected to 4mg/kg lead acetate through intragastric administration lasting 30 days, meanwhile feeded with common feedstuff and deionised water. (2) Zinc protective groups(lead poisoning): Rats in this group weresubjected to 4mg/kg zinc sulfate and 4mg/kg lead acetate through intragastric administration lasting 30 days, meanwhile feeded with common feedstuff and deionised water. (3) Selenium protective groups(lead poisoning): Rats in this group were subjected to 4mg/kg lead acetate and 2mg/kg sodium selenite through intragastric administration lasting 30 days, meanwhile feeded with common feedstuff and deionised water. (4). Cadmium poisoning groups: Rats in this group were subjected to 4mg/kg cadmium chloride through intragastric administration lasting 30 days, meanwhile feeded with common feedstuff and deionised water. (5). Zinc protective groups(cadmium poisoning): Rats in this group were subjected to 4mg/kg zinc sulfate and 4mg/kg cadmium chloride through intragastric administration lasting 30 days, meanwhile feeded with common feedstuff and deionised water. (6). Selenium protective groups (cadmium poisoning): Rats in this group were subjected to 2mg/kg sodium selenite and 4mg/kg cadmium chloride lasting 30 days, meanwhile feeded with common feedstuff and deionised water. (7). Normo-reference groups: Rats in this group were feeded with common feedstuff and deionised water.2. Measure of auditory bainstem response(ABR): ABR and incubation period of wave I were measured. Each group of rats was anesthetized administrated pentobarbital sodium, ABR and incubation period of wave I of 90db and 60db were recorded through different sound intensity irritation in audiometric room used bonding electrodes which were inserted into temporal apophysis, recording electrodes which were inserted into cupular part of head and reference electrodes which were inserted into ear.Results: 1. ABR figures were very clear shapes of wave obviously, incubation period of wave I short and hearing functions is normal in rats of normo-reference groups.2. ABR figures were confused, shapes of ABR almost couldn' t identify, further more, incubation period of waveI was far more long than that of normo-reference groups in rats of lead poisoning groups. All of that show hearing functions of rats in this group were seriously damaged.3. ABR figures were relatively clear, incubation period of wave I was approximate to normal, hearing functions partly recover in rats of zinc protective groups(lead poisoning).Results show that zinc has protective effects on damages of hearing functions caused by lead.4. ABR figures were also relatively clear, incubation period of wave I was approximate to normal, hearing functions partly recover in rats of selenium protective groups(lead poisoning). Results also show that selenium has protective effects on damages of hearing functions caused by lead.5. ABR figures were merely identify in cadmium poisoning groups, incubation period of wave I was far more long than that of normo-reference groups. Results show that hearing functions in this group were seriously damaged by cadmium.6. ABR figures were relatively normal in selenium protective groups (cadmium poisoning) and incubation period of wave I was approximate to normal which show that selenium has protective effects on damages of hearing functions caused by cadmium.7. ABR figures were also relatively normal in zinc protective groups (cadmium poisoning) and incubation period of wave I was approximate to normal. Results show that zinchas protective effects on damages of hearing functions caused by cadmium.Conclusions: Hearing functions of rats could partly damage by lead or cadmium, meanwhile zinc or selenium shows some protective effects on damages caused by them. Results hint that zinc or selenium has some contradict effects to lead or cadmium-induced damages, relieve impairment to hearing functions caused by lead or cadmium.