Aspartate aminotransferase in serum
Apr 25, 2018
Reference values of AST activity in serum are 10-30 IU / l.
AST catalyzes the transfer of the amino group from aspartic acid( amino acid) to a-ketoglutaric acid( keto acid).AST is widely distributed in human tissues( heart, liver, skeletal muscles, kidneys, pancreas, lungs, etc.).There are mitochondrial and cytoplasmic isoenzymes of AST.Normally, the blood serum contains only the cytoplasmic( cytosolic) isoenzyme of AST.
An increase in ACT activity in the blood is observed with a variety of diseases, especially in the defeat of organs and tissues rich in this enzyme. The most dramatic changes in the activity of AST occur when the cardiac muscle is affected. The enzyme activity in 93-98% of patients with MI is increased.
In clinical practice, the simultaneous determination of the activity of AST and ALT in the blood has found wide application;it carries much more clinical information about the localization and depth of the lesion, the activity of the pathological process;allows predicting the outcome of the disease.
With IM AST increases in serum after 6-8 hours, maximum activity reaches 24-36 h and decreases to a normal level by 5-6 days. Expansion of the MI zone leads to the appearance of a second cycle of increased activity. The degree of increase in ACT activity reflects the mass of the myocardium involved in the pathological process. Sometimes the activity of AST increases even before the appearance of electrocardiographic signs of myocardial infarction, and the absence of a decrease in its level after the 3rd-4th day of the disease is prognostically unfavorable. With MI, the activity of AST in the blood can increase 2-20 times.
With angina pectoris, AST activity usually remains within normal limits. However, a number of authors indicate an increase in AST in the severe form of coronary insufficiency in the first 24 hours after the attack and normalization on the 2nd, less often the 3rd day after the attack, as well as with prolonged attacks of paroxysmal tachycardia.
AST also increases with acute hepatitis and other severe lesions of hepatocytes. Moderate increase is observed with mechanical jaundice, in patients with metastases to the liver and cirrhosis. Coefficient de
Fig. Algorithm for making clinical decisions in establishing the etiology of liver damage by the ACT
activity values Fig. The algorithm for making clinical decisions in establishing the etiology of liver damage from the ACT
Rytis activity values, that is, the AST / ALT ratio is normally 1.33, with liver disease below this value, and with heart disease is higher.
The values of ACT activity level( thresholds for making clinical decisions) in establishing a clinical diagnosis of liver damage are presented in Fig. A number of indicators are multipliers multiplied by the value of the upper reference limit for the AST.