Molecular detection and immunological localization of gill Na+/H+ exchanger in the dogfish (Squalus acanthias)
Abbreviated Journal Title
Am. J. Physiol.-Regul. Integr. Comp. Physiol.
acid-base regulation; branchial; elasmobranch; sodium/hydrogen; antiporter; ACID-BASE REGULATION; V-H+-ATPASE; TISSUE DISTRIBUTION; DASYATIS-SABINA; BICARBONATE REABSORPTION; EURYHALINE ELASMOBRANCH; FUNCTIONAL; EXPRESSION; MARINE ELASMOBRANCH; CARBONIC-ANHYDRASE; MYXINE-GLUTINOSA; Physiology
The dogfish (Squalus acanthias) can make rapid adjustments to gill acid-base transfers to compensate for internal acidosis/alkalosis. Branchial Na+/H+ exchange (NHE) has been postulated as one mechanism driving the excretion of H+ following acidosis. We have cloned gill cDNA that includes an open reading frame coding for a 770-residue protein most homologous (similar to 71%) to mammalian NHE2. RT-PCR revealed NHE2 transcripts predominantly in gill, stomach, rectal gland, intestine, and kidney. In situ hybridization with an antisense probe against NHE2 in gill sections revealed a strong mRNA signal from a subset of interlamellar and lamellae cells. We developed dogfish-specific polyclonal antibodies against NHE2 that detected a similar to 70-kDa protein in Western blots and immunologically recognized branchial cells having two patterns of protein expression. Cytoplasmic and apical NHE2 immunoreactivity were observed in cells coexpressing basolateral Na+-K+-ATPase. Other large ovoid cells more generally staining for NHE2 also were strongly positive for basolateral H+-ATPase. Gill mRNA levels for NHE2 and H+-ATPase did not change following systemic acidosis (as measured by quantitative PCR 2 h after a 1- or 2-meq/kg acid infusion). These data indicate that posttranslational adjustments of NHE2 and other transport systems (e. g., NHE3) following acidosis may be of importance in the short-term pH adjustment and net branchial H+ efflux observed in vivo. NHE2 may play multiple roles in the gills, involved with H+ efflux from acid-secreting cells, basolateral H+ reabsorption for pH(i) regulation, and in parallel with H+-ATPase for the generation of HCO3- in base-secreting cells.
American Journal of Physiology-Regulatory Integrative and Comparative Physiology
"Molecular detection and immunological localization of gill Na+/H+ exchanger in the dogfish (Squalus acanthias)" (2008). Faculty Bibliography 2000s. 229.