NA,K-ATPASE SUBUNIT ISOFORM EXPRESSION IN THE GUINEA-PIG ENDOLYMPHATIC SAC

Na,K-ATPase subunit isoform expression was studied by immunocytochemistry in the guinea pig endolymphatic sac, using subunit isoform-specific polyclonal antibodies. Epithelial cells of the guinea pig endolymphatic sac were observed to contain the alpha(1)- and beta(2)-subunit isoforms, and to a lesser extent the beta(1)-subunit isoform, of Na,K-ATPase. The alpha(1)- and beta(2)-subunit isoforms of Na,K-ATPase have been observed previously in other ion and fluid transporting regions of the membranous labyrinth, e.g., stria vascularis and vestibular dark cells. Combined data indicate that the alpha(1)-, beta(2)-form of Na,K-ATPase plays a role in the microhomeostasis of endolymph. The alpha(1)-, beta(2) Na,K-ATPase subunit isoform combination is different from typical ion and fluid transporting tissues, e.g., kidney and colon, and may reflect distinctive characteristics of inner ear Na,K-ATPase.