Studies on gamma-glutamyl transpeptidase of human urine

Studies on serum gamma-glutamyl transpeptidase in primary idiopathic hypothyroidism patients

Variations in the levels of serum gamma-glutamyl transpeptidase (GGT) were measured in control subjects and in 39 adult primary idiopathic hypothyroidism (PIH) patients. The serum GGT activity was low in PIH patients compared to that of control subjects. A more significant correlation was found between serum GGT and T3 (r = 0.766) but not with T4 (r = 0.476). The comparison of serum GGT with TSH has revealed that those two parameters are not parallel with each other (r = -0.454). No significant correlation between serum GGT activity, age, and sex in PIH patients and control subjects was observed. The present available data indicate that measurement of serum GGT might be useful as a marker index in PIH patients.

Gamma-glutamyl transpeptidase in synovial fluid, serum, and urine of patients with rheumatoid arthritis

The changes in the levels of GGT activity in various body fluids, ESR, SF-protein concentration, and SF-WBC count were determined in 59 RA patients and 18 control subjects. The SF-GGT and UGGT were markedly elevated in all RA patients investigated. The increase of SF-GGT is more pronounced than UGGT. The observation of comparable levels of SGGT in RA patients and control subjects indicates that SGGT does not gain entry into synovial fluid or urine. No differences were noticed in SF-protein concentration whereas ESR levels and SF-WBC counts were significantly higher in RA patients than in control subjects. Statistically significant correlations were observed between SF-GGT versus UGGT, SF-WBC, and ESR in females, and between SF-GGT and SF-protein and SGGT in male RA patients. The correlation coefficient values between UGGT versus SF-protein, SF-WBC, and ESR were found to be significant in male RA patients. UGGT levels correlated strongly with SGGT in all RA patients. These findings suggest that the measurement of SF-GGT and UGGT might be useful in understanding the pathogenesis of rheumatoid arthritis.

Studies on urinary gamma-glutamyl transpeptidase in nephrotic syndrome patients

(1) Variations in the levels of GGT were measured in urine specimens taken in the early morning in control and in 20 consecutive adult patients with uncomplicated nephrotic syndrome. (2) The urinary GGT activity was increased in all cases of nephrotic syndrome patients investigated with different etiology. (3) A significant correlation was found between urinary GGT activity and serum albumin (r = 0.727) but not with serum cholesterol (r = 0.129). (4) These findings suggest that enhanced excretion of urinary GGT may be stimulated by decreased albumin concentration or oncotic pressure but does not appear to be due to leakage from plasma. (5) A systematic study on urinary GGT showed that GGT activity was decreased to the upper limit of normal control values in nephrotic syndrome patients after remission.

gamma-Glutamyl transpeptidase excretion in cisplatin-induced acute renal failure

Cisplatin (cisdiamminedichloroplatinum), an important antineoplastic agent, possesses nephrotoxicity as its major side effect. A mild partially reversible nonoliguric form of acute renal failure (ARF) is generally the most common form of nephrotoxicity and occurs in experimental animals following a single dose. gamma-Glutamyl transpeptidase (gamma GT) is an enzyme with maximal activity located in the brush border of proximal renal tubular epithelium. To test the relationship between cisplatin nephrotoxicity and urinary gamma GT excretion, rats received a single 5.5 mg/kg dose of cisplatin and gamma GT excretion was evaluated and compared to anatomic and functional damage. Twenty-four hours following cisplatin administration, there was a marked enhancement of urinary gamma GT excretion, prior to the onset of azotemia. Urinary gamma GT excretion peaked at day 4, then returned to baseline, and decreased to values below baseline on days 8 through 10. By days 11 through 12, renal function and urinary gamma GT excretion had returned to normal. The correlation between nephrotoxicity, changes in urinary gamma GT excretion, and anatomic damage was excellent. Morphologically, increased gamma GT excretion was associated with loss of microvilli, and the return of urinary gamma GT excretion to normal correlated with their regeneration. We conclude that cisplatin administration results in increased urinary gamma GT excretion. This early enhancement, prior to the onset of azotemia, may provide a useful noninvasive marker of early cisplatin nephrotoxicity.

Gamma-glutamyl transpeptidase activity in human urine

The gamma-glutamyl transpeptidase (EC 2.3.2.2) activity of the urine was determined in 369 cases, with L-gamma-glutamyl-p-nitranilide as substrate. Thermally stable, low molecular mass inhibitors were removed by dialysis. The enzyme activity was found to have a mean of 10.57 U/l for the normal neonate population, and a mean of 16.92 U/l for children. A significant increase in activity was observed in pyelonephritis, Alport's syndrome, Wilms' tumour and glomerulopathies. The highest activities were found in kidney diseases associated with renal insufficiency. This non-invasive test can be used for the evaluation of tubular disorders in childhood.

Variants of gamma-glutamyl transferase in human urine

When dialyzed human urine was subjected to ultracentrifugation, gamma glutamyl transferase activity amounting to one-third or less of the total activity was found associated with the microsomal fraction and the remaining in the 100 000 X g supernatant. By ion-exchange chromatography on DEAE-cellulose at pH 7.5, the urinary enzyme was resolved into two fractions. The less anionic form (eluted with 0.15 mol/l NaCl) corresponded to the 100 000 X g supernatant fraction. The more anionic form (eluted with 0.5 mol/l NaCl) corresponded to the microsomal fraction. On chromatography on concanavalin A-sepharose, the urinary transferase activity separated into the unbound fraction and the bound fraction (eluted with alpha-methyl-D-glucoside). The bound fraction was retained more tightly on DEAE-cellulose (eluted with 0.5 mol/l NaCl). The unbound fraction had weaker interaction with the ionic-exchanger (eluted with 0.15 mol/l NaCl). Each of two fractions separated by affinity chromatography on concanavalin A-sepharose, resolved into two bands on cellulose acetate electrophoresis at pH 7.t. In addition, during gel chromatography on Sephadex G-200, they separated into a high molecular weight (greater than 200 000) fraction and a low molecular weight (55 000) fraction. The band that stayed at the origin during electrophoresis was high molecular weight in nature, whereas the fraction that moved towards the anode was found to be the smaller form of the enzyme. The study of the variants of urinary gamma glutamyl transferase was not found to be of clinical significance. The nature and origin of the variant forms of the enzyme in urine are discussed.

Structural, functional, and clinical aspects of gamma-glutamyltransferase

GGT catalyses the transfer of gamma-glutamyl residues to amino acids or small peptides. A number of publications report the purification of GGT, the rat kidney enzyme being the best characterized. Bromelain treatment liberates an active form with a molecular weight of 68,000 separable into two nonidentical glycopeptides with molecular weights of 46,000 and 22,000; the latter contains the gamma-glutamyl binding site. GGT is intimately concerned in the synthesis and metabolism of glutathione through the gamma-glutamyl cycle. There is good evidence that this plays a role in the absorption of amino acids from the glomerular filtrate and from the intestinal lumen through a translocation mechanism. Many studies indicate that the GGT content of liver is increased by enzyme-inducing drugs and that this increase is reflected in elevated activity of the enzyme in blood serum. The serum assay has potential in monitoring drug compliance. Increased serum GGT activity encountered in chronic alcoholics seems to be partly due to microsomal enzyme induction. Utility of the assay in detecting alcoholism is controversial, but it is a useful index to compliance with therapy. Dramatic increases in activity are found in many chemically-induced animal tumors, and can be recognized in premalignant cells long before any morphological changes become evident. It has been used as a test for hepatic metastases, but its predictive value has shown a wide range in the hands of many authors. A similar controversy applies to its role in monitoring cancer therapy. Many synthetic substrates have been used to measure serum GGT activity. Currently, L-gamma-glutamyl-p-nitroanilide is the most popular. Males have higher values than females; activity is very high in the neonate and rather low in pregnancy. The most universal application of serum GGT assay is in diagnosis of liver and biliary tract disease. It is widely believed that higher values occur in biliary obstruction than in parenchymal disease. However, the percentage incidence of abnormalities and the overlap of values in individual cases in different disease categories are so great that the enzyme cannot be recommended for this purpose. Isoenzyme analyses have been performed in an attempt to improve the diagnostic specificity of the serum GGT assay. Tissue-specific patterns have not been described, and disease-specific patterns cannot be reproduced with confidence. Whereas exciting advances are being made in understanding the molecular structure, mechanism, and functions of the enzyme it has yet to find a genuinely useful diagnostic role substantiated by a convincing body of scientific data.