Ammonia Transportation Via Rhesus Glycoproteins In Lonhorned Sculpin (Myoxocephalus Octodecemspinosus) And Spiny Dogfish (Squalus Acanthias).

The maintenance of homeostatic equilibrium is one of the main challenges facing marine fishes. Ammonia is a toxic byproduct of protein digestion and therefore must be regulated and excreted. Since the discovery of Rhesus glycoproteins roles in ammonia excretion in 2007, many species of fish have been studied (Nakada et al. 2007b). Rhesus glycoprotein orthologs, Rhag, Rhbg, Rhcg1, and Rhcg2, have been localized to the gillsof Takifugu rubripes, the puffer fish, while Rhp2 has been localized to the kidney of the marine elasmobranch Triakis scyllium, the banded houndshark. This study looked at the marine elasmobranch Squalus acanthias, spiny dogfish, and the marine teleost Myoxocephalus octodecemspinous, longhorned sculpin. We hypothesize that both the spiny dogfish and the longhorned sculpin utilize Rhesus glycoprotein orthologs in the excretion and movement of ammonia and its byproducts. To date we have cloned a partial fragment of Rhp2 (1040bp) from the spiny dogfish and partial fragments of Rhag (677bp), Rhbg (661bp), and Rhcg1 (610bp), from the longhorned sculpin. The open reading frame from Rhcg2 (1097bp) was also isolated and showed high similarity to other teleost Rhcg2. In this study, immunohistochemistry was used to localize Rhesus glycoprotein orthologs and various ion transporters to the kidney and gills of the spiny dogfish, and the gills of the longhorned sculpin. Western blot and tissue distribution confirmed expression of Rhesus glycoproteins to the epithelial tissues of the longhorned sculpin.