The relationship between the endolymphatic potential (EP) and the sodium and potassium concentration gradients between endolymph and interstitial fluid was studied both by measuring the EP at varying concentrations of sodium and potassium in endolymph and by measuring the effect of a depressed EP on the concentrations of these cations. Ethacrynic acid was used in dogs to change the concentration of sodium and potassium (meq/liter) in endolymph from 5.8 and 148 to 134 and 24.3, respectively. No change in the EP accompanied these alterations. In a second series of experiments the EP was reduced from + 72 mV to + 31 mV for a mean duration of 20 min. No change in the concentration of sodium and potassium in endolymph was found during the period of reduced EP. These data suggest that there is little relationship between the EP and the sodium and potassium concentrations in endolymph.
Saul W. Brusilow, Ellen Gordes