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Natriuretic Peptide Receptors in the Human Endolymphatic Sac
John L. Dornhoffer, MD;
Christopher Danner, MD;
Shulin Li, PhD
Arch Otolaryngol Head Neck Surg. 2002;128:379-383.
Objective To examine human endolymphatic sac (ELS) tissue for atrial natriuretic
peptide (ANP) receptor subtypes A, B, and C.
Design Pilot study.
Methods Immunohistochemical analysis of human ELS tissue specimens. The ANP
receptors were characterized using the peroxidase/antiperoxidase method and
polyclonal antibodies directed against each receptor subtype. The identity
of the stain regarding receptor subclass was masked from the observer. Human
kidney tissue known to contain all 3 receptor subtypes was used as a control.
Presence of the receptor subclasses was confirmed using reverse transcriptase–polymerase
chain reaction (RT-PCR) techniques.
Subjects Samples of ELS tissue were obtained at autopsy from 3 fresh cadaver
specimens (6 ears) and as surgical specimens from 3 patients (1 for immunohistochemical
analysis and 2 for RT-PCR) undergoing acoustic neuroma resection using the
translabyrinthine approach.
Results The ANP type B receptors demonstrated moderate to strong reactivity
in all 7 specimens, and mild to moderate staining to the ANP type C receptor
was also noted. No appreciable reactivity to the ANP type A receptor was detected
using immunohistochemical techniques. All 3 receptor subclasses were detected
using RT-PCR.
Conclusions The ANP receptors are found within the human ELS, with a predominance
of ANP type B based on the intensity of staining. The ANPs may be involved
in fluid homeostasis in the inner ear. Based on these findings, C-type natriuretic
peptide may be a more effective peptide within the human ELS for fluid regulation
because its binding affinity is virtually exclusive for the ANP type B receptor.
From the Department of Otolaryngology/Head and Neck Surgery, University
of Arkansas for Medical Sciences, Little Rock.
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