Water permeability of the endolymph-perilymph barrier in the guinea pig cochlea

The diffusional water permeability of the endolymph-perilymph barrier was determined in guinea pigs by perfusing the perilymphatic space with tritiated water and measuring the uptake of tritiated water into the endolymph. Assuming that the volume flow across the endolymph-perilymph barrier is negligible for short periods of perfusion, the water permeability of the barrier is approximately 130 times greater than its permeability to K+ in normal guinea pigs.