Electron probe X-ray microanalysis of otoconia in the guinea pig inner ear

By using the electron probe X-ray microanalysis technique, the elemental composition of otoconia was analyzed in the normal adult pigmented guinea pig. In the X-ray spectra of otoconia, the most abundant element was Ca, but significant peaks for P, S, Cl and K were also detected. The comparison of the elemental composition in the utricular and saccular otoconia did not show any significant difference. Regression analysis revealed that the concentrations of Ca and K are related by a linear function in both the utricular and saccular otoconia. Analysis of otoconia of different sizes showed that there were no differences in Ca concentration in small, normal and large otoconia. The comparison of other elemental compositions revealed that P, S, Cl and K in the central part of saccular small otoconia showed higher concentrations than those of normal or large otoconia. P, S, Cl and K in the utricular small otoconia showed relatively higher concentrations. These findings may indicate that the small otoconia are immature or newly generated.