Abstract
In vitro calcium ion turnover into otoconia of adult guinea pigs was investigated by the use of tetracycline. The incubation in tetracycline in vitro clearly demonstrated the deposition of tetracycline (fluorescence) on the outer surface of otoconia. Levels of Ca 2+ uptake in utricular otoconia were higher than those in saccular otoconia. In vitro uptake and/or exchange of Ca 2+ was greater in fluid with a high K +/Na + ratio than in fluid in which the ratio was low. It has been thus indicated that a high K +/Na + ratio in normal endolymph should be more suitable for Ca 2+ uptake and/or exchange to maintain the ionic environment in the inner ear. Sodium dodecyl sulfate treatment of otoconia increased the Ca 2+ uptake. The ability of the otoconia to take up Ca 2+ appears to decline with age. It has been indicated that the organic matrix of otoconia may be one of the inhibitory factors for Ca 2+ uptake in old animals.
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