Fatty acid transport in cartilaginous fish: absence of albumin and possible utilization of lipoproteins

There are conflicting reports over whether albumin is present in the Chondrichthyes. In addition, it is unknown whether given their low levels of extrahepatic beta-oxidation, there is actually a need for a plasma FFA transport system. We examined the plasma of several Chondrichthyan species, including representatives of both the Holocephali and the Neoselachii using a combination of agarose gel electrophoresis, [C-14]palmitic acid binding, SDS-PAGE, and Oil Red O staining following cellulose acetate electrophoresis. None of the eight species examined had a major acidic palmitate-binding protein with the characteristics of albumin and they all lacked proteins with the mass of albumin, 66 kDa. Palmitate was bound to specific plasma proteins in all elasmobranch species examined and these palmitate-binding proteins resembled lipoproteins based on their diffuse and variable mobilities and Oil Red O staining. These lipoproteins are potentially LDL and VLDL based on their migration positions. Albumin appears to be absent from Chondrichthyan plasma and lipoproteins bind LCFA in its absence.