Aspartate aminotransferase (AST)

Aspartate aminotransferase is an indicator of damage to muscle (skeletal or cardiac) or liver cells. It is also found in the kidney. This enzyme is present in the cytosol and mitochondria. It is increased significantly by muscle activity (e.g. seizure, myopathy or exercise), in which case CK is also usually raised unless the injury is already resolving. In hepatocytes, AST is found in higher concentrations in the periacinar zone. In dogs with hepatocellular injury, AST increases tend to parallel ALT. If ALT (or GLDH in large animals) is not raised, look for an extrahepatic source of AST such as muscle. The half-life is short in cats, so even small increases may be significant.

Major differentials for increased AST include muscle trauma or necrosis, hypoxic or circulatory disturbances of the liver (including anaemia), hepatotoxicity, hepatitis, or neoplasia


All species


Plasma or Serum


Gel, Plain or heparin tube

Collection protocol:

Fasted sample preferred.


Reference(s): Center, S.A. Interpretation of Liver Enzymes. In: Veterinary Clinics of North America Small Animal Practice 37:2 March 2007  p 297 – 333. Stockham, S.L and Scott, M.A. Fundamentals of Veterinary Clinical Pathology 2nd Edition 2008