Detection of atrial natriuretic peptide receptor in the labyrinth of the mouse inner ear.
OBJECTIVE
To examine whether the atrial natriuretic peptide receptor (NPR-A) is present in the secretory regions of the membrane labyrinth of the adult mouse inner ear.


METHODS
Recent studies have implied that the homeostasis of endolymph fluid in the inner ear may be regulated by receptor-mediated mechanisms. Several studies have identified the presence of atrial natriuretic peptide receptors in the inner ear of guinea pig and rat. As a member of the natriuretic peptide receptor family, which also includes B-type natriuretic peptide receptor (NPR-B) and C-type natriuretic peptide receptor (NPR-C), NPR-A may be involved in the regulation of fluid homeostasis in the inner ear.


METHODS
In this study, samples of stria vascularis, nonstrial tissue of the cochlear lateral wall and vestibular organ tissue from the ears of 6 adult mice were obtained by immediate excision of bony labyrinth under operating microscope after decapitation. Total RNA was isolated and mRNA was amplified by the reverse transcription-polymerase chain reaction (RT-PCR) using consensus primers flanking a region of 127 bp at the target sequence. Mouse renal cortex known to contain NPR-A was used as a positive control.


RESULTS
We demonstrated that NPR-A was expressed in the mouse stria vascularis as well as in the nonstrial tissue of the cochlear lateral wall and vestibular organ.


CONCLUSIONS
These results suggest that natriuretic peptides may play an important role in maintaining the fluid homeostasis of inner ear endolymph via interaction with NPR-A.
Long
Lili
L
Department of Otorhinolaryngology; West China Hospital of Sichuan University, Chengdu, Sichuan, P.R. China.
Tang
Yuedi
Y
Xia
Qingjie
Q
Xia
Zengliang
Z
Liu
Jin
J