Gamma-glutamyl transferase

GGT is present (in decreasing order of abundance) in proximal renal tubule, liver, pancreas, and intestine. The enzyme is present in cytoplasm (microsomes), but the larger fraction is located in the cell membrane and may transport amino acids and peptides into the cell across the cell membrane in the form of y-glutamyl peptides. It may also be involved in some aspects of glutathione metabolism.  

GGT activity in serum comes primarily from liver. The enzyme in serum is heterogeneous with respect to both net molecular charge (e.g., shown by electrophoresis) and size. These forms appear to derive from posttranslational modifications of a single type of enzyme molecule rather than to be due to the existence of true isoenzymes. For example, high molecular weight forms may represent the release of cell membrane fragments into the circulation. Despite numerous investigations, clear correlations between patterns of multiple forms and particular diseases cannot be discerned. 

Elevated activities of GGT are found in the sera of patients with alcoholic hepatitis and in the majority of sera from people who are heavy drinkers. Increased concentrations of the enzyme are also found in serum of subjects receiving anticonvulsivant drugs such as phenytoin and phe-nobarbital. Such an increase of GGT activity in serum may reflect induction of new enzyme activity by the action of the alcohol and drugs and/or their toxic effects on microsomal structures in liver cells. 

In AMI, GGT activity is usually normal. If there is a rise, it occurs at about the fourth day, reaches a maximum value in another 4 days, and probably implies liver damage secondary to cardiac insufficiency. 

Unlike ALP, GGT is not increased in conditions in which osteoblastic activity is increased. 

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Gamma-glutamyl-transferase activity was determined according to "Monotest 10 y-GT neu" from Boehringer-Mannheim. 

ALT, alanine aminotransferase AST, aspartate aminotransferase GGT, gamma-glutamyl transferase INR, international normalized ratio LDH, lactate dehydrogenase PT, prothrombin time. 

Hepatic Effects. Liver function tests (serum bilirubin, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase) completed in 11 hexachloroethane workers were within the normal range (Selden et al. 1994). Plasma hexachloroethane levels in these workers, who wore protective equipment, were 7.3 + 6.04 pg/L at the time of the tests (Selden et al. 1993). Mild skin and mucous membrane irritation were reported in the exposed group, suggesting that exposure may have been through either the inhalation or dermal routes of exposure. 

Hepatic Effects. Liver function tests (serum bilirubin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase) were not affected in 11 hexachloroethane-exposed workers who wore protective clothing (Selden et al. 1993). 

Alcohol consumption is very difficult to assess. There is widespread belief that individuals underreport their intake and there are no reliable laboratory tests available for definitive diagnosis of alcohol abuse. A combination of abnormalities in the plasma activity of gamma-glutamyl transferase (GGT or yGT), AST and reduction in erythrocyte mean cell volume (MCV) maybe useful and all are routine lab. tests. A potential marker of interest is carbohydrate-deficient transferrin (CDT) which is an abnormal isoform of serum transferrin arising due to defects in the attachment of carbohydrate chains to the protein core. Unfortunately, CDT is a somewhat specialized test, not performed by most laboratories. Other markers which have attracted some research interest are ethyl sulphate and ethyl glucuronide. Excretion in the urine of these metabolites occurs for up to 50 hours after binge drinking so they offer a useful index of recent heavy alcohol intake. 

When we received her back she was on a low and peculiar dose of methadone, and it transpired that she had recently been reducing this by 2ml in the daily dosage every two weeks, at her own request. In the interview there was an obvious smell of alcohol, and assessment soon revealed that Sandra was drinking heavily every day, with her gamma glutamyl transferase coming back at several hundred international units per litre. 

Traynor. O.J., Lee, Y.C., Whittaker, K.B., Zinsmeister, A.R., Moss, D.W. Wood. C.B. (1988) Gamma glutamyl transferase aetivity in rat eolon during experimental colonic carcinogenesis. J. surg. Oncol., 37, 52-55... 

Hepatic Effects. A study that measured levels of several liver enzymes (alanine amino transferase, aspartate amino transferase, gamma glutamyl transferase, and alkaline phosphatase) found no significant differences between workers exposed to silver and insoluble silver compounds and those with no history of silver exposure (Pifer et al. 1989). 

Increased liver function tests - Mrs CR s alanine aminotransferase (ALT), alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) levels are all increased above the normal ranges and indicate moderate liver impairment. This may have implications on the ability of the liver to metabolise drugs and must be borne in mind when prescribing any drugs that are metabolised by it. 

Gamma-glutamyl transferase (GGT) is found in the liver, but this test is relatively non-specific. It is released following tissue damage and is raised in cholestasis in parallel with ALP. GGT release is stimulated by alcohol and some drugs (such as phenytoin and carbamazepine), and therefore the GGT level can be used to assess abstinence in alcoholics, like Mrs MW. 

V.M., Silva, A.E.B. Role of gamma-glutamyl transferase activity in patients with chronic hepatitis C virus infection. X. Gastroenterol. Hepatol. 2003 19 314-318... 

A 69-year-old man was given amiodarone intravenously 1500 mg for multiple coupled ventricular extra beats and 24 hours later developed acute hepatitis, with a 50-fold increase in serum transaminase activities and simultaneous increases in lactate dehydrogenase, gamma-glutamyl transferase, bilirubin, and prothrombin time there was a moderate leukocytosis and mild renal insufficiency (182). No further amiodarone was given and there was full recovery within 2 weeks. Other causes of acute hepatitis were excluded. 

Severe overdosage of sodium aurothiopropanol sulfonate (1.1 g daily for 13 days) caused jaundice and skin eruptions. Liver biopsies showed modest centrilobular necrosis and significant bile stasis. Serum hepatic enzyme activities were increased. The patient was treated with dimercaprol and recovered after 2 months, although alkaline phosphatase and gamma-glutamyl-transferase activities remained high for 6 months. 

When considering the application of urinary enzymes to monitor subtle renal dysfunction and/ or to clarify mechanisms of nephrotoxicity, only a limited number of enzymes have been generally accepted as valuable urinary biomarkers. These include lactic dehydrogenase, N-acetyl-P-l>glucosarriitiidase (NAG), alanine aminopeptidase (AAP), intestinal alkaline phosphatase, glutathione-S-transferase, gamma-glutamyl transferase and fructose-l,6,-biphosphatase. 

E373 Ng, R.H., Altaffer, M., Mukadam, H.A., O Neill, M. and Statland, B.E. (1987). Performance of the Kodak Ektachem DTSC module for the determination of alkaline phosphatase and gamma glutamyl transferase. Clin. Chem. 33, 937, Abstr. 279. 

E519 Franzini, C., Cattozzo, G. and Morelli, A. (1989). Gamma-glutamyl transferase assay Results from two closed analytical systems equalized by mathematical manipulation. Biochim. Clin. 13, Suppl. 1/8, 310, Abstr. B 160. 

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