What is aspartate aminotransferase

Aspartate aminotransferase is an important substance in the human body. The high and low changes in the level of aspartate aminotransferase can effectively reflect whether a person suffers from heart, liver and other diseases. Therefore, when you go to the hospital for a physical examination, the doctor will check the aspartate aminotransferase in the patient's body. For example, if the liver is damaged, the aspartate aminotransferase level will be high. Today's article will give readers detailed knowledge about aspartate aminotransferase.

Aspartate aminotransferase (AST) is mainly distributed in the myocardium, followed by the liver, skeletal muscle and kidney. Under normal circumstances, the AST content in serum is low, but when the corresponding cells are damaged, the cell membrane permeability increases, and the AST in the cytoplasm is released into the blood, so its serum concentration may increase. Clinically, it is generally used as an auxiliary examination for myocardial infarction and myocarditis. The normal value of aspartate aminotransferase is 0 to 40 units/L. When aspartate aminotransferase is significantly elevated and the aspartate aminotransferase/alanine aminotransferase (ALT) is greater than 1, it indicates extensive damage to the liver parenchyma and a poor prognosis.

Clinical significance

1. In acute viral hepatitis, serum AST activity may increase significantly, generally 10 to 30 times the upper limit of the normal reference value, and not higher than the serum ALT activity measured at the same time. When the increase in serum AST activity continues to exceed ALT activity, it indicates that the hepatitis lesions are chronic and progressive.

2. The serum levels may be normal or slightly elevated in patients with cirrhosis, liver cancer, hepatic congestion, and biliary obstruction.

3. AST is most abundant in myocardial cells. Serum AST activity increases during myocardial infarction. Serum AST activity begins to rise 6 to 8 hours after onset and reaches a peak at 18 to 24 hours. The peak AST activity is proportional to the size of the infarct. If no new infarction occurs, the enzyme activity will return to normal after 4 to 5 days; if it rises again, it indicates that the infarction focus has expanded or a new infarction has occurred.

4. Myositis, crush syndrome, muscle injury, nephritis and pneumonia can also cause increased serum AST activity.

Combined with the AST/ALT ratio, further judgments can be made about liver disease. When the ratio is 1, especially >2, it indicates severe liver disease, mainly of the necrotic type.

5. Others: Some drugs that are toxic to the liver, such as luminal, diazepam, phenacetin, furans, etc., can increase AST concentrations.