gamma-Glutamyl transpeptidase of human seminal fluid

A sandwich enzyme-linked immunosorbent assay for human seminal gamma-glutamyl transpeptidase

A sandwich enzyme-linked immunosorbent assay (ELISA) was developed for detecting human seminal gamma-glutamyl transpeptidase (gamma-GTP) using a combination of anti-seminal gamma-GTP monoclonal antibodies. These monoclonal antibodies did not react with human ovary or uterus in immunohistochemical study. Optimal assay condition, resulting in a sensitive assay with a low background, is presented. The detection limit of this assay was estimated to be 1 ng/ml of seminal gamma-GTP corresponding to about 100,000 times dilution of seminal sample. This ELISA was specific for seminal gamma-GTP, without cross-reactivity to renal or hepatic gamma-GTP, normal blood serum, non-coital vaginal fluid or saliva. The recovery of seminal gamma-GTP added to various biological fluids were also examined.

Immunocytochemical study of seminal gamma-glutamyltransferase using monoclonal antibodies

We produced three monoclonal antibodies, SG1, SG2 and SG3, specific for human seminal gamma-glutamyltransferase when characterized by enzyme-linked immunosorbent assay and immunoblotting. Seminal gamma-glutamyltransferase was localized, by immunostaining, to the epithelial cells of the ductus epididymidis, seminal vesicle and prostate gland with SG1, those of the prostate gland with SG2, and those of the seminal vesicle with SG3. Rabbit polyclonal anti-seminal gamma-glutamyltransferase serum reacted with the proximal convolution of the kidney and the bile capillaries of the liver, and with the epithelial cells of the reproductive organs. However, immunoreactivity was not observed in the kidney or liver with the monoclonal antibodies. Thus, these monoclonal antibodies are probably all specific to seminal gamma-glutamyltransferase but recognize different epitopes.

Enzymatic and electrolytic profiles of human semen

Chemical parameters comprising urea and creatinine nitrogen, cations (Na+, K+, and Ca2+), chloride, phosphorus, protein, cholesterol and enzymes, aminotransferases, alkaline and prostatic acid phosphatases, gamma-glutamyltransferase, creatine kinase, and lactate dehydrogenase were ascertained for semen from groups A (vasectomized), B (oligospermic), and C (normospermic) men, 19 to 55 years of age. Of the parameters, the vasectomized group underwent definite depressions in potassium ion, alkaline phosphatase, aspartate aminotransferase, gamma-glutamyltransferase, and lactate dehydrogenase as compared with the normospermic group; the last three enzymes and, possibly, the urea-creatinine ratio were decreased for the oligospermic group vs. the normospermic men. In the comparison of groups A and B, only the decrements in alanine aminotransferase and lactate dehydrogenase were statistically significant. In corroboration of past reports, CK-BB comprised the main isoenzyme of semen creatine kinase.

Multiple biochemical tumor markers in seminoma. A double-blind study

The value of certain biochemical tumor markers have been well established in nonseminomatous testicular cancer. However, the lack of frequent tumor markers in the sera of patients with seminoma has prompted us to embark on this double blind study. The authors studied 89 patients with the histologic diagnosis of seminoma utilizing placental alkaline phosphatase (PLAP), gamma-glutamyl transpeptidase (gamma GT), human chorionic gonadotropin (hCG), and alpha-fetoprotein (AFP). It was found that 12/30 patients (40%) with active tumor had elevated serum PLAP and 10/30 (33%) of these patients had elevated serum levels of GGT. Eighty percent of the patients with clinically active tumors had detectable serum levels of one or more of these biochemical markers. Since the frequency of the previous tumor markers have been scarce in seminoma, these serial utilization of these biochemical markers should assist the clinician to detect and monitor seminoma patients more efficaciously. However, the false-positive, false-negative, rates, and biologic half lifes of these markers should be taken in account.

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.

Evidence for the prostatic origin of gamma-glutamyltranspeptidase activity in human semen

Gamma-glutamyltranspeptidase activity and fructose concentration have been measured in 100 semen samples, in 7 split ejaculates and in the seminal fluid of a patient with congenital absence of ductus deferens and seminal vesicles. Evidence is presented that the prostate is the major source of gamma-glutamyltranspeptidase in human semen.