Ototoxic interaction between noise and pheomelanin: distortion product otoacoustic emissions after acoustical trauma in chloroquine-treated red, black, and albino guinea pigs.

This study provides further evidence of an ototoxic interaction between red pheomelanin pigmentation and noise-induced hearing loss. Red, black, and albino guinea pigs were treated with a low, a high, or no dose of chloroquine. The 2f1-f2 distortion product otoacoustic emission (DPOE) measurements were measured before, immediately after, and 1 month after noise exposure to a 1-kHz tone at 105 dB SPL for 72 hours. In red guinea pigs, the DPOE was severely affected by noise trauma when treated even by a low single dose of chloroquine, whereas in both albino and black guinea pigs, the chloroquine effect on the DPOE was temporary and present only when the drug was given in a high single dose. The structure most likely to be responsible for the severe loss of DPOE in chloroquine-treated red animals is the strial melanocyte. The damage may be triggered by an ototoxic noise-induced production of radical oxygen species from pheomelanin, for example, by the Fenton reaction or due to the increased variability of the melanocyte 1 receptor gene as in red-haired individuals.