Permeability to potassium of the endolymph-perilymph barrier and its possible relation to hair cell function.

The endocochlear potential and potassium concentrations in endolymph and perilymph were simultaneously measured in the basal turn of the guinea pig cochlea with double-barreled K+ selective electrodes. The K+ conductance and K+ permeability coefficient of the endolymph-perilymph barrier were calculated from the rate of change of endolymph K+ concentration relative to the K+ electrochemical potential difference recorded during permanent anoxia. When anoxia was induced in guinea pigs treated with kanamycin, the rate of decline of the electrochemical potential difference for K+ between the endolymph and perilymph was reduced when compared to normal guinea pigs. In guinea pigs exposed to broad band noise at 115 dBA for periods from 11-15 days, the rate of decline of the electrochemical potential difference for K+ across the endolymph-perilymph barrier was reduced but not to the extent found in guinea pigs treated with kanamycin. The K+ conductance and K+ permeability coefficient of the endolymph-perilymph barrier showed substantial decreases in noise exposed and kanamycin treated guinea pigs, as compared to normal guinea pigs. The magnitude of decrease of K+ permeability of the endolymph-perilymph barrier by noise or kanamycin was correlated with suppression of the maximum output of the cochlear microphonic.