Lysosomal Enzymes in the Inner Ears of Kanamycin-Treated Guinea Pigs

Abstract

The activity of acid phosphatase, N-acetyl-β-glucosaminidase and β-glu-curonidase were localized histochemically in 36 guinea pigs injected daily with kanamycin sulfate (250 mg/kg body weight) for 1 to 6 weeks. All three lysosomal enzymes showed essentially the same distribution pattern. Before the well-known microscopic damage developed in the outer hair cells, there was a temporary slight increase in intensity and area of enzyme activity. Afterwards, the histochemical reaction became gradually weaker and finally was negative. The inner hair cells underwent the same changes, but later. Ultimately all hair cells were destroyed by this ascending process. Likewise, in the spiral ganglion cells enzyme activities initially increased, then markedly diminished. These changes started in the apical turn and descendingly involved also the lower turns. Enzyme activities in the spiral ganglion cells returned to normal after cessation of treatment. It appears that histochemical changes in the ganglion cells are independent of the damage to the organ of Corti and therefore not associated with the well-known secondary changes in the ganglion.