Ultracytochemical study of Corti's organ in guinea pigs

Abstract

Ca-ATPase activity, which is involved in the transport of Ca ions, was demonstrated cytochemically in Corti's organs of guinea pig inner ears and compared with Mg-ATPase, Na-K-ATPase and ALPase activities. The reaction products of Ca-ATPase ac-tivity were observed on the plasma membranes of hair cells, especially in the apical portion and in the hairlets. Moreover, the precipitate was also found in the basal portion and in the plasma membrane of the nerve endings. Both inner and outer pillar cells were completely devoid of reaction precipitate, as were the surface plasma membranes of the phalanges of the phalangeal cells. In the epithelial cells of the inner spiral sulcus, border cells, Hensen's cells and Claudius' cells, a strong reaction was observed in the surface plasma membrane facing the endolymphatic space. The location of Mg-ATPase activity was very similar to that of Ca-ATPase except that it was also found on the surface plasma membrane of the phalanges of the phalangeal cells facing the endolymph. ALPase activity was never observed in Corti's organ. Na-K-ATPase activity was detected only on the cytoplasmic side of the plasma membranes of the hairlets.
The co-existence of Ca-ATPase and Na-K-ATP-ase, especially in the hair cells, may be important for the exchange of Ca and Na ions that initiates the excitation of these acoustic receptors.