Identification and characterisation of urea transporters in the gills of the spiny dogfish, Squalus acanthias.

Elasmobranchs possess a unique system for osmoregulation. They are slightly hyperosmotic compared to their environment due to high levels of urea and trimethylamino oxide in their body. Therefore, they absorb water continuously by osmosis and do not have to drink. This system creates an enormous urea gradient at the gills, which is supposedly maintained by urea back-transporters. This study aims at identifying and characterizing these transporters.