DETECTION OF C-TYPE NATRIURETIC PEPTIDE (CNP) AND ATRIAL-NATRIURETIC-PEPTIDE (ANP-B) RECEPTOR MESSENGER-RNAS IN RAT INNER-EAR

C-TYPE natriuretic peptide (CNP) is the third member of the natriureti c peptide family which plays an important role in body fluid homeostas is. To determine a possible role of CNP in regulation of an inner ear fluid, we investigated the expression of CNP and atrial natriuretic pe ptide B receptor (ANP-B receptor) mRNAs in rat inner ear using a rever se transcription polymerase chain reaction (RT-PCR) method. Amplificat ion products with sizes expected for CNP and ANP-B were detected in th e inner ear. After cloning and analysis, the sequences for PCR product s were identical to those of CNP or ANP-B receptor in the brain. These results indicate that both CNP and ANP-B receptor are expressed in th e inner ear of the rat and suggest that CNP may play a role in inner e ar function (such as regulation of inner ear fluid) in an autocrine an d/or paracrine manner.