蝸牛脂質代謝に関する研究(第2報)

生化学的および組織化学的研究

抄録

The lipid metabolism in the guinea pig cochlea was studied biochemically and histochemically. The results from this study, together with the results obtained by autoradiographic study (ref. 1st report), were discussed. Following conclusions were obtained.
1) Autoradiographic study by perilymphatic perfusion of the guinea pig cochlea with 3H-glycerol proved to be fit for the purpose of investigation on the localization of the phospho-lipid metabolism activity in the cochlea. In the autoradiographic study, the most heavily labelled celles were the outer hair cells, especially intensive along the cell membrane, where there were the sheets of endoplastic reticulum (subsurface cisterna). It would appear that subsurface cisterna in the outer hair cells synthesize phospholipids and then supply other biomembranes with these phospholipids.
2) Kanamycin depressed the incorporation of 3H-glycerol into the membranous cochlea. Auto-radiographic study demonstrated that this depression was due to the decreased incorporation of 3H-glycerol into the hair cells.
3) The turnover of phosphatidyl choline was the most rapid and the rate of decrease in this lipid content by kanamycin was the highest among the all lipid fractions. It seems that inhibition of phosphatidyl choline metabolism as well as that of polyphosphoinositides by aminoglycosidic antibiotics is closely related to the mechanism of cell injury by these drugs.
4) Histochemical and autoradiographic studies showed that the lipid globules in Hensen's cells contained hydrophilic lipids. These data, together with other data, suggest that the globules may function as an energy source as well as mechanical support of the organ of Corti.
It is desirable that the prospective advances of the research on the lipid metabolism in the cochlea will contribute to discovery of a preventive and a treatment for sensori-neural hearing loss. The present study suggests that CDP-choline is useful for a preventive or a treatment.