Carbonic Anhydrase VI in the Mouse Nasal Gland

Abstract

S U M M A R YWestern blotting analysis of mouse nasal tissue using a specific anti-mouse secreted carbonic anhydrase (CA VI) antibody has shown that CA VI is present in this tissue. A single immunoreactive band of 42 kD was observed, as has been found previously for salivary tissues. RT-PCR analysis has shown that nasal mucosa expressed CA VI mRNA. By immunohistochemistry (IHC), CA VI was observed in acinar cells, in duct contents of the anterior gland of the nasal septum, and in the lateral nasal gland. The Bowman's gland, the posterior gland of the nasal septum, and the maxillary sinus gland were negative. Immunoreactivity was also observed in the mucus covering the respiratory and olfactory mucosa and in the lumen of the nasolacrimal duct. In contrast, an anti-rat CA II antibody (that crossreacts with the mouse enzyme) stained only known CA II-positive cells and an occasional olfactory receptor neuron. These results indicate that CA VI is produced by the nasal gland and is secreted over the nasal mucosa. By reversible hydration of CO 2 , CA VI is presumed to play a role in mucosal functions such as CO 2 sensation and acid-base balance. It may also play a role in olfactory function as a growth factor in maturation of the olfactory epithelial cells.

Immunohistolocalization and Gene Expression of Secretory Carbonic Anhydrase Isoenzyme CA-VI in Canine Nasal Cavity

“…The CA-VI mRNA expression in each canine nasal tissue coincided with the immunohistochemical findings. Both immunohistochemistry and RT-PCR have detected CA-VI signals in the murine respiratory region, nasal epithelial cells and serous acinar cells [15], and only RT-PCR has identified CA-VI in humans [35].…”

“…The physiological roles of nasal CA-VI might be to provide a greater buffering capacity in the nasal mucosa, to protect the upper respiratory tract against excessive acidity [15,19] and electrolyte transportation via epithelial cells [5]. Excessive organic acids or endogenous acid generated from CO 2 could be rapidly neutralized by the CA enzymes [1,30,32].…”

“…Together with other cytosolic carbonic anhydrases in humans, CA-VI might work to neutralize the excessive organic acidic milieu produced by microbial flora in dental and epithelial surface cells [17]. In the respiratory tract, immunohistochemistry and real-time PCR have detected CA-VI in the nasal mucosa, lower airways and lungs of guinea pigs, humans and mice [15,19,28,35]. The suggested roles of CA-VI in these areas include the maintenance of pH homeostasis, protecting the upper respiratory tract against excessive acidity, and transporting electrolytes via epithelial cells.…”

Immunohistochemical Localization and Gene Expression of Carbonic Anhydrase Isoenzymes CA-II and CA-VI in Canine Lower Airways and Lung

“…The immunohistochemical distribution of CA-II has been determined in the respiratory system of humans [15] and rats [2], while that of CA-VI has been reported for mice [7] and rats [8]. Recently, canine CA-VI was detected in the upper respiratory tract, in particular, in the nasal cavity [16].…”

“…Mucosal defense systems are required for the trachea and bronchus because the covering epithelium of the airway is always exposed to a wide range of chemical, physical, and microbial acidic stresses [7,8]. CA-II and CA-VI are powerful contributors to the production of bicarbonate ion [8].…”