Modification of atrial natriuretic peptide receptor expression in the rat inner ear.
OBJECTIVE
The purpose of this animal study was to confirm the presence of all three atrial natriuretic peptide (ANP) receptor subtypes in the rat inner ear and compare the expression of each receptor after inner ear injection of ANP, phosphate-buffered saline, or a solution containing ANP incubated with anti-ANP antibody (to block upregulation).


BACKGROUND
Receptors for ANP and related compounds have been localized in the inner ear of animals and humans. A previous study at this institution demonstrated the ability to up-regulate the expression of the three ANP receptors (ANP-A, ANP-B, ANP-C) in response to round window injection of ANP in the rat inner ear.


METHODS
After surgical exposure, the round window of female Lewis rats was injected with various concentrations of ANP, ANP plus anti-ANP antibody, or control. Animals were killed 24 hours after injection, inner ear tissues were harvested and homogenized, and RNA was isolated for reverse-transcription polymerase chain reaction.


RESULTS
Electrophoresis showed the presence of all three receptor subtypes with exposure to phosphate-buffered saline. Expression was significantly higher 24 hours after injection with the two concentrations of ANP. This increase was partially blocked with increasing relative concentrations of anti-ANP antibody.


CONCLUSIONS
These findings confirm the presence and responsiveness of ANP receptors in the rat inner ear. The ability to block up-regulation with the antibody provides a potential new research tool for manipulating the function of this hormone system in experimental models and, ultimately, in understanding the mechanisms of fluid homeostasis in the inner ear.
Boone
Ryan T
RT
Department of Otolaryngology-Head and Neck Surgery, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
Zuo
Chunlai
C
Fan
Chun-Yang
CY
Dornhoffer
John
J
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D009320:Atrial Natriuretic Factor / Q000008:administration & dosage / Q000276:immunology / Q000494:pharmacology*; D002021:Buffers; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D007758:Ear, Inner / Q000187:drug effects* / Q000378:metabolism*; D004587:Electrophoresis, Agar Gel; D005260:Female; D007267:Injections; D010710:Phosphates; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D017461:Receptors, Atrial Natriuretic Factor / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012405:Round Window, Ear; D012965:Sodium Chloride / Q000737:chemistry / Q000494:pharmacology; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects
D000906:Antibodies; D002021:Buffers; D004338:Drug Combinations; D010710:Phosphates; D020033:Protein Isoforms; D012333:RNA, Messenger; D012965:Sodium Chloride; D009320:Atrial Natriuretic Factor; D017461:Receptors, Atrial Natriuretic Factor