Regulation of vocal fold transepithelial water fluxes

Vocal fold hydration is critical to phonation. We hypothesized that the voc al fold generates bidirectional water fluxes, which are regulated by activi ty of the Na+-K+ ATPase. Western blots and immunohistochemistry demonstrate d the presence of the alpha -subunit Na+-K+ -ATPase in the canine vocal fol d (n = 11). Luminal cells, basal and adjacent one to two layers of suprabas al cells within stratified squamous epithelium, were immunopositive, as wel l as basolateral membranes of submucosal seromucous glands underlying trans itional epithelia. Canine (n = 6) and ovine (n = 14) vocal fold mucosae exh ibited transepithelial potential differences of 8.1 +/-2.8 and 9.3 +/-1.3 m V (lumen negative), respectively. The potential difference and short-circui t current (ovine = 31 +/-4 muA/cm(2); canine = 41 +/- 10 muA/cm(2)) were su bstantially reduced by luminal administration of 75 muM acetylstrophanthidi n (P<0.05). Ovine (n = 7) transepithelial water fluxes decreased from 5.1<p lus/minus>0.3 to 4.3 +/-0.3 mul.min(-1).cm(-2) from the basal to luminal ch amber and from 5.2 +/-0.2 to 3.9 +/-0.3 mul.min(-1).cm(-2) from the luminal to basal chamber by luminal acetylstrophanthidin (P<0.05). The presence of the Na+-K+ -ATPase in the vocal fold epithelium and the electrolyte transp ort derived from its activity provide the intrinsic mechanisms to regulate cell volume as well as vocal fold hydration.