Distribution and possible function of lysosomal enzymes in the inner ear under normal and pathophysiological conditions.

The normal distribution of several lysosomal enzymes was studied in 20 guinea pigs. In the outer hair cells lysosomal enzymes are mainly localized at the apical cell pole, while in inner hair cells the distribution was uniform. Nonlysosomal enzymes like alcaline phosphatase are of predominantly basal localization. The concentration of some lysosomal enzymes like N-acetyl-beta-glucosaminidase was higher in outer than in inner hair cells while others like acid phosphatase, beta-glucuronidase and sulfatase showed a stronger reaction in the inner hair cells. After 10 days of sound overstimulation with 120 dB for 1 h a day, there was an increase of lysosomal enzyme content namely in the outer hair cells. There was no change of non-lysosomal enzymes. Under these conditions there might be a partial destruction of cellular organelles eliminated by lysosomal activity without loss of a total cell. In addition the distribution and possible function of lysosomal enzymes in other labyrinthine tissues was discussed.