Sodium and Potassium Ions in Endolymph: In Vivo Measurements With Glass Microelectrodes

Abstract

IN 1906, Cremer reported that when a thin glass membrane was interposed between two aqueous solutions, an electric potential difference was observed which was very sensitive to change in acidity.¹Horovitz and Schiller later found that the introduction of boron oxide caused glass electrodes to become nearly as sensitive to Na⁺as to H⁺.¹In 1957, Eisenman et al^1,2characterized the range of glass composition which had sufficiently high selectivities for Na⁺or K⁺to be practical for use in the measurement of Na⁺, on the one hand, or K⁺, on the other. Hinke^1,3,4constructed Na⁺and K⁺glass microelectrodes to measure the intracellular activities of these cations. Khuri^1,5further developed the cation sensitive microelectrode for biological use. In 1954, Smith et al⁶using a flame photometer reported that endolymph of the inner ear of the guinea pig had a high potassium and low