Effect of streptomycin on the supporting cells of the utricular macula.

Morphological changes in utricular supporting cells in the guinea pig following streptomycin sulfate (SM) intoxication were investigated ultrastructurally in vitro, using an organ culture system. The intracellular structures of the supporting cells, such as the nucleus, mitochondria, and Golgi apparati were well preserved after 7 days in culture. After 10 and 14 days in culture, the supporting cells degenerated. The organ culture system was applied to ototoxicity studies on the supporting cells in utricular macula within 7 days after explanation. When the utricles were exposed to 3, 10 and 30 mg/ml of SM for 3 days, the number of granules in the supporting cells decreased markedly and the number of lysosomes increased daily. The lysosomes contained mitochondria, myeloid bodies, granules and vesicles. Acid phosphatase (AcPase) activity decreased in Golgi apparati and lysosomes. When the concentration of SM was reduced to 3 and 10 mg/ml, the damage to the supporting cells was less marked than that in cells exposed to 30 mg/ml. The supporting cells showed a dose-dependent response with respect to morphological damage. After 3 days culture with 30 mg/ml of SM, the specimens were subsequently cultured for 4 days in a medium without SM. After removal of SM from the medium, lysosomes decreased in number, and the granules and the endoplasmic reticulum showed a gradual increase. The AcPase activity was determined in both lysosomes and Golgi apparatus. This study revealed that the morphological changes in the supporting cells can be reversible.