Effect of gentamycin on the melanosomes in the stria vascularis of the pigmented guinea pig: an ultrastructural study.

Melanosomes of the stria vascularis in gentamycin (GM)-intoxicated guinea pigs were examined ultrastructurally. Experimental animals were given GM sulfate intramuscularly in a daily adjusted dose of 100 mg/kg for 15 consecutive days (group A), and 150 mg/kg for 5 consecutive days (group B). Melanosomes of the intermediate cells in group B significantly increased in number in comparison with those in group A and the control group. Melanosomes in the apical turn outnumbered those in the basal turn in all three groups. Cytochemically, Na+, K(+)-ATPase activity was also demonstrated in the marginal cells. There was little difference in the degree of enzyme activity between groups A, B and the control group. The role and significance of melanosomes of the stria vascularis are discussed.