IMPACT OF HEAVY METALS ON VESTIBULAR SENSORY ORGANS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The inner ear in humans contains hearing and balance organs. Chronic exposure to heavy metals causes damages to auditory component of the inner ear resulting in hearing loss. Exposure also causes imbalance in children and adults by affecting the balance organ that functions with the aid of tiny calcium carbonate crystals (otoconia). The production and function of the otoconia are controlled by the protein material embedded. Toxic metals when incorporate into the protein matrix of the otoconia may cause abnormalities in the formation of the tiny crystals that is consequently manifested by hearing and balance disorders. To understand the impact of heavy metal exposure on the biomineralization of human otoconia, we proposed to investigate toxic impact of heavy metals, mercury, cadmium and lead, on similar biominerals (otoliths) in the ears of fish. Otolith organs are also made of calcium carbonate. The protein material within an otolith controls the crystal form and size of the otolith. The hypothesis based on the fact that heavy metals incorporate to biominerals by direct deposition as well as by binding to the organic matrix (proteins). Depending on the magnitude of exposure, toxicity of particular metal and levels incorporated, they may inhibit or alter the normal development and function of the otolith. To test the hypothesis, it was proposed that zebrafish would be exposed to the metals in water, then the otoliths would be removed and analyzed for the metals to elucidate their levels and distribution between inorganic and organic material.