The expression of endothelin type A and B receptors in the lateral wall of the mouse cochlea.

Endothelin (ET), originally characterized as a vasoconstrictive peptide, has been found to have many different biological functions, including acting as a local hormonal regulator of pressure, fluid, ions and neurotransmitters in the inner ear. The objective of this study was to examine and quantify the mRNA expression of the endothelin type A and B receptors (ETAR and ETBR) in the strial vascularies (StV) and non-strial tissues (NSt) of the cochlear lateral wall using the real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) technique. The mouse tissue samples were harvested and RNA was extracted. RT was performed to obtain cDNA, and then the mRNA expression of each gene was measured via real-time PCR. We found that both receptor subtypes were expressed in the cochlear lateral wall, with a predominance of ETAR over ETBR. We showed that the mRNA expression of the two receptor subtypes was higher in the StV with a 1.8 times higher level of ETAR and an 8.1 times higher level of ETBR mRNAs than in the adjacent NSt of the lateral wall tissue. This study shows the existence and the quantity of ET receptor subtypes in the StV and NSt of the mouse cochlea. Our results suggest that an endothelin-mediated response via two different receptors, ETAR and ETBR, may play an important role in the physiological functions of the cochlear lateral wall by maintaining the homeostatic environment of the cochlea.