Differential Expression of Rh Glycoproteins in the Sea Lamprey, (Petromyzon marinus)

Ammonia is a by-product of protein metabolism. It is a nitrogenous waste that if not excreted, its accumulation is toxic. The exact mechanism by which ammonia is excreted has been a point of controversy for many years. Rh glycoproteins have been recently linked to ammonia excretion in a broad range of organisms, including the fishes. It has been shown that Rh isoforms; Rhag, Rhbg, Rhcg1, and Rhcg2 have been localized in the gills of the teleost, Takifugu rubripes and mediate the transport of an ammonia analogue (methylammonium) in vitro. Very little is known about the ability of the more primitive fishes, in particular the agnathans to regulate nitrogenous wastes. In this study we have used immunohistochemistry and western blot analysis to localize several members of the Rh glycoprotein family to various epithelial tissues of the lamprey Petromyzon marinus.