Aspartate transaminase levels

When administering the HMG-CoA reductase inhibitors and the fibric acid derivatives, the nurse monitors the patient s fiver function by obtaining serum transaminase levels before the drug regimen is started, at 6 and 12 weeks, then periodically thereafter because of the possibility of liver dysfunction with the drugs. If aspartate aminotransferase (AST) levels increase to three times normal, the primary care provider in notified immediately because the HMG-CoA reductase inhibitor therapy may be discontinued. 

Determination of the level of cytosolic enzymes such as aspartate transaminase, alanine transaminase, and lactate dehydrogenase is part of standard biochemical liver function tests to measure hepatocellular necrosis [2, 101]. Cytosolic enzymes are not subject to genetic variations inherent in microsomal enzyme production. Liver cytosolic enzymes metabolize several molecules, of which galactose and amino acids are typical examples, used for hepatic function tests. 

In a 40-week study in which rats were administered 2-hexanone at 400 mg/kg/day, the levels of liver enzymes (alanine aminotransaminase and aspartate transaminase activities) measured at 4- week intervals were normal (Eben et al. 1979). 

Q4 Cardiac enzymes are released into the blood following heart muscle damage during a heart attack. Creatine kinase, particularly its MB isoenzyme, is one of the most specific of these enzymes, which reaches a peak 24 hours after infarction. It rises and then falls within the first 72 hours of the heart attack. Aspartate transaminase is also released, but levels of this enzyme can be raised in several other conditions, so it is less specific than creatine kinase MB. Troponin T is also specific for myocardial damage and is raised for approximately two weeks following infarction. Finding a high concentration of these enzymes in a patient s blood therefore supports the evidence obtained from the ECG and confirms that the patient has suffered a myocardial infarction. 

Many important steps in nitrogen metabolism occur in the liver. Liver disease can be severe enough so that urea production may be compromised. Blood urea nitrogen (BUN) levels will decrease, and levels of the toxic compound ammonia will increase. Because the liver is involved in converting bilirubin to the diglucuronide that is excreted in the bile, the levels of bilirubin will increase in the body and jaundice will occur. When liver cells are damaged, enzymes such as aspartate transaminase (AST, also known as GOT, glutamate-oxaloacetate transaminase) will leak into the blood. 

The brain pallidal Ti-weighed MRI signal hyperintensity was recorded in 10 women and 11 men (33-69 yrs) with chronic liver disease and the data were correlated with self-reported clinical neurological symptoms and blood serum Fe, Mn, bilirubin, alk. phosphatase and aspartate transaminase, erythrocyte Mn, and blood Hb and hematocrit levels. 

Kock et al. (1994) reported death of 7 of 20 black rhinoceroses that had been held in creosote-treated holding pens. The animals that died had uniformly swollen intensely green livers, containing excessive intrahepatic bilirubin. Serum levels of aspartate transaminase (AST) and bilirubin were also elevated. However, doses and routes of exposure were not established in this study. 

Percy Veere s laboratory studies showed that his serum alanine transaminase (ALT) level was 294 units/L (reference range = 5-30), and his serum aspartate transaminase (AST) level was 268 units/L (reference range = 10-30). His serum alkaline phosphatase level was 284 units/L (reference range for an adult male = 40-125), and his serum total bilirubin was 9.6 mg/dL (reference range = 0.2-1.0). Bilirubin is a degradation product of heme, as described in Chapter 44. 

A possible explanation for the superiority of the amino donor, L-aspartic add, has come from studies carried out on mutants of E. coli, in which only one of the three transaminases that are found in E. coli are present. It is believed that a branched chain transaminase, an aromatic amino add transaminase and an aspartate phenylalanine aspartase can be present in E. coli. The reaction of each of these mutants with different amino donors gave results which indicated that branched chain transminase and aromatic amino add transminase containing mutants were not able to proceed to high levels of conversion of phenylpyruvic add to L-phenylalanine. However, aspartate phenylalanine transaminase containing mutants were able to yield 98% conversion on 100 mmol l 1 phenylpyruvic acid. The explanation for this is probably that both branched chain transaminase and aromatic amino acid transminase are feedback inhibited by L-phenylalanine, whereas aspartate phenylalanine transaminase is not inhibited by L-phenylalanine. In addition, since oxaloacetate, which is produced when aspartic add is used as the amino donor, is readily converted to pyruvic add, no feedback inhibition involving oxaloacetate occurs. The reason for low conversion yield of some E. coli strains might be that these E. cdi strains are defident in the aspartate phenylalanine transaminase. 

Hepatocellular damage manifests as elevated serum aminotransferases [alanine aminotransferase (ALT) and aspartate aminotransferase (AST)]. The degree of transaminase elevation does not correlate with the remaining functional metabolic capacity of the liver. An AST level two-fold higher than ALT is indicative of alcoholic liver damage. 

Opiates can effect serum levels of enzymes and other substances whose homeostatic control depends on clearance through the liver (F8, G12, M15, N4, S19). In one reported case, the aspartate aminotransferase was within normal limits before the administration of codeine, but within 2 hours after the drug, the enzyme activity had risen to two times the normal value by 8 hours to eight times the normal activity, and within 24 hours it had returned to normal (F8). Increases in transaminase to levels 5-85 times the control value have been reported in 6 of 16 patients with disease of the biliary tree following the administration of codeine phosphate (2 grains) (B7, F8). Gross has shown that morphine, codeine, or mepheridine administration produce elevations of serum amylase or lipase (G12). These elevations have been attributed to constriction of the sphincter of Oddi and increased intraductal pressure on the pancreatic duct (G12, N4). 

---