( ALT )IS FOUND EXCLUSIVELY LOCATED IN THE LIVER; IT IS RELEASED INTO THE BLOOD STREAM AS THE RESULT OF LIVER INJURY. 
AST IS NORMALLY FOUND IN A VARIETY OF TISSUES INCLUDING LIVER, HEART, MUSCLE, KIDNEY AND BRAIN. IT IS RELEASED INTO THE SERUM WHEN ONE OF THESE TISSUES IS DAMAGE. FOR EXAMPLE (AST) LEVEL IN SERUM IS ELEVATED IN HEART ATTACKS OR WITH MUSCLE INJURY