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Ototoxicity of kanamycin in albino and pigmented guinea pigs. I. A morphologic and electrophysiologic study
Abstract:
Ototoxic drugs of the aminoglycoside type have been shown to accumulate to melanin, suggesting a possible mechanism for their ototoxicity. The present study was undertaken by combining electrophysiologic and morphologic methods to investigate whether the ototoxicity of kanamycin is different in pigmented and albino guinea pigs. In pigmented animals a kanamycin dose of 200 mg per kilogram of body weight per day resulted in hearing loss together with loss of both inner and outer hair cells. The albino animals in the same dose group showed significantly less hearing loss and hair cell degeneration. With daily doses of 20 and 60 mg/kg/day, no difference in ototoxicity was found between the pigmented and albino animals. The results support the hypothesis that affinity of kanamycin to inner ear melanin might be responsible for the difference in ototoxicity between albino and pigmented guinea pigs.
Insights
Aminoglycoside ototoxicity may be linked to melanin. Kanamycin caused more hearing loss and hair cell damage in pigmented guinea pigs than albino ones, supporting this melanin-affinity hypothesis.
Area of Science:
- Oto-pharmacology
- Auditory Neuroscience
- Toxicology
Background:
- Aminoglycoside drugs, like kanamycin, are known to cause ototoxicity.
- These drugs have shown an affinity for melanin, suggesting a potential mechanism for ototoxicity.
- Pigmentation differences in animal models may influence drug toxicity.
Purpose of the Study:
- To investigate the role of melanin in kanamycin-induced ototoxicity.
- To compare the ototoxic effects of kanamycin in pigmented versus albino guinea pigs.
- To correlate electrophysiologic and morphologic findings with pigmentation.
Main Methods:
- Combined electrophysiologic and morphologic assessments were used.
- Kanamycin was administered to pigmented and albino guinea pigs at varying doses (20, 60, and 200 mg/kg/day).
- Hearing loss and hair cell degeneration were evaluated.
Main Results:
- At a high dose (200 mg/kg/day), pigmented guinea pigs exhibited significantly greater hearing loss and hair cell degeneration than albino counterparts.
- At lower doses (20 and 60 mg/kg/day), no significant difference in ototoxicity was observed between pigmented and albino groups.
- These findings suggest a dose-dependent effect related to pigmentation.
Conclusions:
- The study supports the hypothesis that kanamycin's affinity for melanin contributes to its ototoxicity.
- Inner ear melanin may play a crucial role in the differential ototoxic effects observed between pigmented and albino animals.
- This highlights the importance of pigmentation in understanding aminoglycoside-induced hearing loss.