Expression of Aquaporins in the Cochlea and Endolymphatic Sac of Guinea Pig

Abstract

It has been shown that the aquaporin (AQP) family forms membrane pores selectively permeable for water and some small solutes such as glycerol and urea, and thus plays important roles in regulating the fluid in many organs involved in fluid transport such as kidney, lung and brain. The aims of the present study were to investigate the cellular localization and its significance of aquaporins (AQPs) in various subregions of the cochlea and endolymphatic sac of guinea pig. The expression patterns of AQP1, 2, 3 and 4 were immunolabeled with the specific polyclonal rabbit antibodies against the rat AQP1, 2, 3 and 4. Our immunohistochemical examination showed that in the cochlea, AQP1, 3 and 4 were widely distributed in various locations including stria vascularis, spiral ligament, the organ of Corti and spiral ganglion in the similar patterns except that AQP3 in the stria vascularis was lightly weaker than AQP1 and AQP4. AQP2 was labeled only in Reissner’s membrane. In the endolymphatic sac, AQP1, AQP3 and AQP4 were strongly expressed in the epithelial cells and subepithelial cells similarly with the exception that AQP3 was lightly weaker than AQP1 and AQP4. No AQP2 immunoreactivity was detected in the endolymphatic sac. Theses results suggest that different members of the AQP family in the labyrinth may work in concert to regulate endolymph and to maintain homeostasis in the inner ear.

Immunohistochemical localization of aquaporins in the human inner ear

“…AQPs 2, 3, 5, 7, 8, 9, and 10). However, previous studies have reported the expression of AQPs in the inner ear of several animal models (Fukushima et al 2004;Huang et al 2002;Merves et al 2003;Zhong and Liu 2003). For example, AQP2 is expressed in the endolymphatic sac of guinea pig and human (Couloigner et al 2004).…”

“…In the inner ear, expression of AQPs 1, 2, 4, and 5 has been reported in the rat, mouse, and guinea pig (Beitz et al 1999(Beitz et al , 2003Huang et al 2002;Li and Verkam 2001;Merves et al 2003;Mhatre et al 1999Mhatre et al , 2002aMiyabe et al 2002;Sawada et al 2002Sawada et al , 2003Stankovic et al 1995;Takumi et al 1998;Zhong and Liu 2003). Dysfunction or lack of AQPs has been described in a variety of diseases, such as nephrogenic diabetes insipidus, early onset of cataract, Sjogren's syndrome, wet lung syndrome, congestive heart failure, and brain edema (for reviews, see Agre et al 2002;Agre and Kozone 2003).…”

Expression of aquaporins and vasopressin type 2 receptor in the stria vascularis of the cochlea

“…Since the discovery of aquaporin (AQP) water channels (Agre et al, 1993), it has become clear that these channels play a crucial role in water homeostasis not only in the kidney but also in the inner ear. Indeed, expressions of proteins and/or mRNAs of AQPs in the inner ear have already been reported including negative reports (AQP-1: Stankovic et al, 1995;Sawada et al, 2003;AQP2: Kumagami et al, 1998;Beitz et al, 1999;Merves et al, 2000;Mhatre et al, 2002;Sawada et al, 2002;Fukushima et al, 2005;Zhong and Liu, 2003;AQP-3: Beitz et al, 1999;AQP-4: Takumi et al, 1998;Minami et al, 1998;AQP-5: Beitz et al, 1999;Mhatre et al, 1999;Löwenheim and Hirt, 2004;AQP-6: Fukushima et al, 2002;Lopez et al, 2007;Taguchi et al, 2008;AQP-7: Beitz et al, 1999;Huang et al, 2002;AQP-8: Beitz et al, 1999;Huang et al, 2002;and AQP-9: Huang et al, 2002). However, previous reports have had many contradictions.…”

Molecular Analysis of Aquaporin Genes 1 to 4 in Patients with Menière’s Disease

“…Among the AQPs, isoforms 1-4 are the best studied in the inner ear and have been proposed to be involved in the pathophysiology of MD. AQP1 has been detected in the intermediate cells of the stria vascularis in rats and in nonsensory epithelial cells in the spiral ligament in humans [16][17][18]. Likewise, the immunolocalization of AQP4 in humans closely resembles the one seen in animal models [7,17,19].…”