モルモット前庭器耳石のカルシウム変化

Abstract

Morphological and elemental analyses of otoconia under normal and pathological condition following streptomycin intoxication were carried out using scanning electron microscopy and energy dispersive X-ray microanalysis.Young pigmented guinea pigs were used in this study. In the control group, typical cylindrical otoconia in the superficial layer of otolithic membrane had abundant calcium, and were used as a standard (=100%). On the surface of supporting cells, two types of globular substances were observed. One had 14% calcium content compared to the standard, and the other had 2.5%, although these could not be distinguished morphologically. The former may be a precursor of otoconia, while the latter may be a precursor of the otolithic membrane and subcupular meshwork. In the deep portion of the otoconial layer, immature otoconia had 15-30% calcium. On the dark cells of the ampullary area, oval shaped otoconia with a lower calcium content (30%) were observed at the utricular side. At the canal side, round shaped otoconia with a lower (12%) calcium content were observed.In the streptomycin treated group, the globular substances on the supporting cells contained markedly less calcium. On the surface of the otolithic membrane, giant otoconia were observed. Their calcium content was reduced to about 35%. On the dark cells of the ampullary area, only round shaped otoconia were observed in both sides. Calcium content was lower (20%) at the utricular side, but the same as the control (12%) at the canal side. Non-calcium elements were detected in both sides.These observations suggest that streptomycin may affect not only the sensory hair cells but also the supporting cells and the dark cells, and thus may interfere with the ion regulating system of the inner ear.