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MBBS QUESTION #10359
Question 1
In liver injury, serum ALT and AST (aminotransferases) are commonly measured together, with ALT considered more liver-specific than AST. This is primarily because:
  • ALT is concentrated mainly in hepatocyte cytosol with relatively low activity elsewhere, while AST is also abundant in cardiac muscle, skeletal muscle, kidney, and red blood cells✔️
  • AST is found exclusively within the liver, with no activity in any other tissue
  • ALT has no measurable activity in any organ besides the liver under any circumstance, making it perfectly specific
  • Both enzymes are equally distributed and equally liver-specific
Correct Answer Explanation
Because AST is present in significant amounts in multiple tissues besides liver (heart, skeletal muscle, kidney, red cells), its elevation is less specific for hepatocellular injury; ALT, being relatively concentrated in the liver, is considered the more liver-specific marker, though both are used together with their ratio to help characterize the pattern of liver disease (e.g., alcoholic hepatitis classically shows AST > ALT).