Manganese accumulation in the mouse ear following systemic exposure

There is evidence in human populations that exposure to manganese (Mn), or Mn in combination with excessive noise exposure, results in hearing loss. Quantitative reverse-transcriptase polymerase chain reaction revealed expression of the metal transporters DMT1, ZIP8, and ZIP14 in control mouse ears. ZIP8 is known to have a high affinity (K(m) = 2.2 microM) for Mn transport, and ZIP8 protein was localized to the blood vessels of the ear by immunohistochemistry. We treated mice (strains C57BL/6J and DBA/2J) with Mn (100 mg/kg MnCl(2), by subcutaneous injection, on three alternating days), and Mn was significantly elevated in the ears of the treated mice. Mn concentrations remained elevated over controls for at least 2 weeks after treatment. These studies demonstrate that metal transporters are present in the mouse ear and that Mn can accumulate in the ear following systemic exposure. Future studies should focus on whether Mn exposure is associated with hearing deficits.