AJP - Renal Physiology, Vol 253, Issue 1 50-F58, Copyright © 1987 by American Physiological Society
Na and nonelectrolyte entry into inner ear fluids of the rat
O. Sterkers, E. Ferrary, G. Saumon and C. Amiel
Kinetics of hydrophilic solute entry into endolymph (EL), perilymph (PL),
and cerebrospinal fluid (CSF) were studied after intravenous administration
(sodium, urea, glycerol, mannitol, sucrose) and cerebral lateral ventricle
injection (urea, sucrose) of tracers in anesthetized rats. Samples of
cochlear EL, PL of scala vestibuli (PLV), PL of scala tympani (PLT), and
cisternal CSF were obtained. The data showed slow entry of tracers in PLV,
PLT, and CSF as follows: Na greater than urea greater than mannitol
approximately sucrose; slower entry of mannitol and sucrose in PLT and CSF
than in PLV; 1 h delayed peak of radioactivity in PLV compared with the
immediate peaks in PLT and CSF after CSF injection, and the value of PLV
peak was 13% that in CSF; extremely slow entry of nonelectrolytes in EL.
These results indicate that PLV originates mainly from plasma across a
blood-perilymph barrier that restricts the entry of small hydrophilic
solutes. The blood-perilymph barrier is most likely composed of an
endothelial barrier associated with an epithelial secretion. The latter
could be located at the vasculo-epithelial zone of the spiral limbus.
