Na-K-Atpase Activity in the Cochlea of the Rat During Development

Abstract

The development of the Na-K-activated ATPase enzyme system was studied in the stria vascularis of rats from 6-46 days post partum. In 68-day-old animals a rather high Na-K-ATPase activity was observed. Thereafter the activity increased gradually until the 12th day. A surprisingly sharp increase of the Na-K-ATPase activity was found from 12–18 days. The adult level was reached between 19 and 25 days after birth, which coincides with the functional maturity of the cochlea. These data, together with comparable data on the development of the ERP and the ionic composition of the endolymph, confirm the assumption that the Na-K-ATPase system in the stria vascularis is responsible for the maintenance of the cation gradients and for the generation of the ERP.