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Absence of extrahepatic lipid oxidation in a freshwater elasmobranch, the dwarf stingray Potamotrygon magdalenae : Evidence from enzyme activities

1989; Wiley; Volume: 251; Issue: 3 Linguagem: Inglês

10.1002/jez.1402510312

1097-010X

Thomas D. Singer, James S. Ballantyne,

Aquaculture disease management and microbiota

Abstract Measurements of key enzymes in several metabolic pathways in five tissues were undertaken in a freshwater elasmobranch, the dwarf stingray Potamotrygon magdalenae , with special emphasis on enzymes of lipid and ketone body oxidation. The metabolic organization of this freshwater elasmobranch resembles that of the marine elasmobranchs studied to date with some slight differences noted. As has been observed in marine elasmobranchs, lipid oxidation occurs largely in the liver. Other tissues, especially heart, may rely on the oxidation of other substrates, in particular amino acids. Amino acids appear to be very important metabolites for both oxidative and gluconeogenic tissues perhaps because of a reduced requirement for urea synthesis. Ketone bodies, especially beta‐hydroxybutyrate, although less important in the freshwater elasmobranch than in marine forms, can be used by both marine and freshwater elasmobranchs, and this distinguishes them metabolically from all teleosts examined to date.