PRELIMINARY-STUDY OF THE ROLE OF ENDOTHELIN-1 IN THE HOMEOSTASIS OF THE INNER-EAR

Endothelin (ET), originally characterized as a 21-residue vasoconstric tor peptide from endothelial cells, has been reported to act as a loca l hormonal regulator of pressure, fluid, ions, and neurotransduction. Our previous studies suggested an important role of ET-1 in the inner ear. The present study investigated the time kinetics of ET-1 in the e pithelium of the endolymphatic sac (ES) of guinea pigs and its relatio n to the development of endolymphatic hydrops (EH) following locally m ounted secondary immune reaction. In the duration between 12 h and day 1, ET-l-like activity completely disappeared from the epithelium of t he ES and was associated with the accumulation of inflammatory cells i n the ES and a rapid development of EH. On day 7, ET-1-like activity r ecovered as a consequence of the decrease of inflammatory cells and re duction of EH. These findings suggest that ET-1 may play an important role as one of the regulators maintaining the fluid balance.