Pendrin immunoreactivity in the gill epithelium of a euryhaline elasmobranch

1 Department of Zoology and 2 College of Medicine, University of Florida, Gainesville, Florida 32611; and 3 Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892 Pendrin is an anion exchanger in the cortical collecting duct of the mammalian nephron that appears to mediate apical Cl /HCO exchange in bicarbonate-secreting intercalated cells. The goals of this study were to determine 1 ) if pendrin immunoreactivity was present in the gills of a euryhaline elasmobranch (Atlantic stingray, Dasyatis sabina ), and 2 ) if branchial pendrin immunoreactivity was influenced by environmental salinity. Immunoblots detected pendrin immunoreactivity in Atlantic stingray gills; pendrin immunoreactivity was greatest in freshwater stingrays compared with freshwater stingrays acclimated to seawater (seawater acclimated) and marine stingrays. Using immunohistochemistry, pendrin-positive cells were detected on both gill lamellae and interlamellar regions of freshwater stingrays but were more restricted to interlamellar regions in seawater-acclimated and marine stingray gills. Pendrin immunolabeling in freshwater stingray gills was more apical, discrete, and intense compared with seawater-acclimated and marine stingrays. Regardless of salinity, pendrin immunoreactivity occurred on the apical region of cells rich with basolateral vacuolar-proton-ATPase, and not in Na + -K + -ATPase-rich cells. We suggest that a pendrin-like transporter may contribute to apical Cl /HCO exchange in gills of Atlantic stingrays from both freshwater and marine environments. anion exchanger; vacuolar-proton-adenosinetriphosphatase; sodium-potassium-adenosinetriphosphatase; sodium chloride regulation; acid/base regulation; Dasyatis sabina