Identification and Sequence of the Na, K-ATPase Alpha Sub-Unit of the Bull Shark, Carcharhinus leucas

The bull shark, Carcharhinus leucas, is rare amongst the elasmobranchs in that it is able to tolerate both seawater and freshwater. Elasmobranch body fluids are hyperosmotic (~600-1100 mOsm 1^-1) in both seawater (~900-1000 mOsm 1^-1) and freshwater (~100 mOsm 1^-1) environments. Despite this high osmotic concentration, the plasma salt concentrations are maintained at a level similar to that of other marine fish. This is achieved by efficient transport and regulation of water and ions which requires the expression and function of a number of membrane transporters which are fundamental to osmoregulation, including the Na, K-ATPase (sodium pump). Using RT-PCR we have amplified, cloned sequenced a number of cDNAs encoding the partial sequence of the bull shark Na, K-ATPase alpha subunit. The nucleotide and putative amino acid sequences will analysed and compared to those published for other species.