Alanine aminotransferase in serum
Apr 20, 2018
Reference values of ALT activity in serum are 7-40 IU / l.
ALT catalyzes the transfer of the amino group from alanine( amino acid) to a-ketoglutaric acid( keto acid).ALT is found in skeletal muscles, liver, heart. In the heart muscle, it is much less than AST.In smaller quantities, ALT is also found in the pancreas, spleen, lungs. The highest concentration of ALT reaches the liver.
The increase in the activity of aminotransferases ( AST and ALT) is considered 1.5-5 times higher than the upper limit of the norm as a moderate hyper enzyme, 6-10 times as hyperfermentemia of an average degree, more than 10 times as high. The degree of uptake of aminotransferase activity is indicative of the severity of the cytolytic syndrome, but does not directly point to the depth of disturbances in the organ's proper function.
In patients with MI, an increase in ALT activity in serum is detected in 50-70% of cases, more often with extensive necrosis of the heart muscle. The greatest increase in ALT activity is detected in the acute phase - an average of 130-150% of the norm, which is noticeably inferior to that of AST - an average of 450-500% of the norm.
In liver diseases, ALT activity changes most significantly in comparison with AST.In acute hepatitis, regardless of its etiology, the activity of aminotransferases increases in all patients. Especially the activity of ALT contained in the cytoplasm, due to its rapid exit from the cell and entering the bloodstream, is especially changing, so the determination of ALT activity is a more sensitive test for the early diagnosis of acute hepatitis than AST.The half-life of ALT is approximately 50 h. AST is located mainly in the mitochondria, its half-life is 20 h, therefore its activity rises with more severe damage to the hepatocyte. The activity of ALT and AST increases 10-15 days before the appearance of jaundice in hepatitis A, and for many weeks with hepatitis B( the activity of these enzymes increases simultaneously, but ALT - to a much greater extent).In a typical course of viral hepatitis, ALT activity peaks at the 2-3rd week of the disease. With its favorable course, ALT activity normalizes after 30-40 days, AST - after 25-35 days. A repeated or progressive increase in aminotransferase activity indicates a new necrosis or relapse of the disease. The prolongation of the period of increased activity of aminotransferases is often an unfavorable sign, since it may indicate the transition of an acute process to a chronic one.
In the acute period of viral hepatitis in all forms, except for severe forms, the de Ritis coefficient varies from 0.55 to 0.65, with a heavy current this coefficient averages 0.83, which reflects a more significant
increase in AST activity. In the differential diagnostic sense, it is of some importance that in cases of alcoholic liver damage, in contrast to viral diseases, a predominant increase in AST activity is characteristic( the de Ritis coefficient is more than 2).
For chronic hepatitis is characterized by moderate and average hyperfertility.
With latent forms of liver cirrhosis, no increase in enzyme activity is usually observed. In active forms, a persistent, although insignificant increase in aminotransferase activity is detected in 7477% of cases.
Bilirubin-aminotransferase dissociation deserves attention, that is, cases of severe hyperbilirubinemia( mainly due to direct bilirubin) and low aminotransferase activity. This dissociation is observed with podepitelnoy jaundice with stable bile hypertension, acute hepatic insufficiency. The activity of AST and ALT, as well as alkaline phosphatase, increases with the resolution of chronic heart failure( peak usually 3-4 days).
Increased activity of ALT and AST can be detected in practically healthy carriers of hepatitis B surface antigen, which indicates the presence of externally asymptomatic active processes in the liver.