Characteristic ionic composition of endolymph is maintained in cultured inner ear.

Inner ear anlagen from mouse were explanted on the 16th gestational day (gd) and cultured for 5 days, i.e. corresponding to the time of birth. By using energy dispersive X-ray technique an elemental composition characteristic for endolymph was found within the membranous labyrinth of the explants. The sodium to potassium ratio in the endolymphatic space of the cultured inner ears corresponded to endolymph of the 16th gd fetus in vivo. There was no difference in the endolymph compartment between the cochlear and vestibular halves of the in vitro specimens. Differences in Na to K ratio between endolymph of the inner ears and the surrounding medium were statistically significant. Thus, endolymph-regulating mechanisms are active also under organ culture conditions, although not fully optimal.