Aspartate Transaminase

Aspartate Transaminase (AST), formerly called Serum Glutamate Oxaloacetate Transaminase (SGOT), is an intracellular enzyme present in:

• Liver
• Heart (cardiac muscle)
• Skeletal muscle
• Kidney
• Brain
• RBCs

It catalyzes:
Aspartate + α-ketoglutarate → Oxaloacetate + Glutamate

1️⃣ Hepatocellular Injury

AST is released into blood when liver cells are damaged.

Elevated in:

• Acute viral hepatitis
• Toxic hepatitis
• Drug-induced liver injury
• Cirrhosis

🔎 In liver disease:

• Both AST and ALT rise
• ALT is more liver-specific
• AST levels are usually lower than ALT in acute hepatitis

2️⃣ Alcoholic Liver Disease

📌 Important clinical point:

• AST:ALT ratio > 2:1 suggests alcoholic liver disease
• Due to mitochondrial damage and pyridoxal phosphate deficiency

3️⃣ Myocardial Infarction (Historical Use)

AST was previously used as a marker for:

Acute myocardial infarction (MI)

Pattern:

• Rises within 6–12 hours
• Peaks at 24–36 hours
• Returns to normal in 3–5 days

⚠ Now replaced by:

• Troponin
• CK-MB

4️⃣ Muscle Disorders

Elevated in:

• Muscular dystrophy
• Severe muscle injury
• Rhabdomyolysis
• Trauma

Since AST is present in muscle, levels increase with muscle damage.

5️⃣ Hemolysis

Mild increase may occur due to:

• Hemolytic anemia
• Hemolyzed blood samples

Normal Reference Range

AST: ~8–40 IU/L (varies by laboratory)