Vacuolar proton-ATPase expression in the gills of a euryhaline stingray Effects of environmental salinity

Piermarini, P.M.; Evans, D.H.

Journal of Experimental Biology 204(19): 3251-3259

2001


ISSN/ISBN: 0022-0949
Accession: 036024941

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Abstract
In the gills of freshwater bony fishes (teleosts), recent evidence has linked active sodium uptake to the activity of a vacuolar proton-ATPase (V-H-ATPase). This V-H-ATPase has been immunolocalized to respiratory pavement cells and mitochondrion-rich (MR) chloride cells. In rainbow trout (Oncorhynchus mykiss), branchial V-H-ATPase activity and expression are negatively correlated with environmental salinity. In the gills of cartilaginous fishes (elasmobranchs), V-H-ATPase has been immunolocalized to MR cells in a stenohaline marine species (Squalus acanthias), but the effects of environmental salinity has not been examined. The goals of this study were to describe V-H-ATPase expression in the gills of a euryhaline elasmobranch, the Atlantic stingray (Dasyatis sabina), and determine what influence environmental salinity has on branchial V-H-ATPase expression. Immunochemical techniques were used to describe and compare expression of the V-H-ATPase; we used a heterologous antibody to the V-H-ATPase B-subunit. Immunoblots on gill tissue membrane fractions revealed that the antibody recognized a 60 kDa peptide, which is the expected molecular weight for the B-subunit. The abundance of the V-H-ATPase B-subunit in gills of freshwater stingrays was approximately 7.5 times higher than in seawater stingray gills. Immunohistochemistry demonstrated that V-H-ATPase was localized to MR cells of gill lamellae and interlamellar regions in freshwater stingrays. In seawater stingrays, V-H-ATPase was only localized to MR cells of gill interlamellar regions. These results may suggest that gills from freshwater stingrays may have a higher V-H-ATPase activity than seawater stingrays. This indicates that branchial V-H-ATPase may perform an important function in freshwater stingrays, presumably the energization of active sodium uptake.