The presence and localization of receptors for atrial natriuretic peptide in the inner ear of the guinea pig

Summary

Atrial natriuretic peptide (ANP) is a cardiac hormone known to mediate increased capillary permeability, vasodilation, and natriuresis. Since specific receptors for ANP exist in both the eye and brain, possibly playing a role in ocular and cerebrospinal fluid regulation, we postulated that ANP might also be involved in inner ear fluid dynamics. Autoradiography was used to evaluate whether and where ANP receptors are present in the inner ear. Frozen sections of the cochlea and vestibular organ from guinea pigs (n=18) were incubated in either ¹²⁵J-ANP alone or together with an excess of unlabeled ANP (as control). ANP receptors were demonstrated in the stria vascularis of the cochlea and in the secretory epithelium of the ampulla and the utriculus, but not in the region of the sensory cells. These results indicate that (1) specific ANP receptors are present in the inner ear, and (2) their local distribution is congruent with those parts thought to regulate labyrinthine fluid composition and volume. We speculate that ANP contributes to the homeostasis of the inner ear fluids and may even play a role in the pathophysiology of Menière's disease.