γ-GTP Activity Research Articles

Role of testosterone in γ-glutamyltranspeptidase-dependent renal methylmercury uptake in mice

To elucidate the mechanisms responsible for sex and age differences in renal methylmercury uptake, effects of castration and testosterone treatment on mercury content and activity of renal γ-glutamyltranspeptidase (γ-GTP), which supposedly plays an important role in renal mercury, were investigated in mice. Between 2 and 8 weeks of age, renal methylmercury uptake in male mice determined 4 hr after injection of a nontoxic dose of methylmercuric chloride (MMC, 1 μmol/kg, sc) increased about fivefold. At 4 weeks of age, a significant sex difference in renal mercury uptake first appeared. Renal mercury content in 4-week-old male mice was twofold higher than that of females and increased with age, but remained constant in females. Small but significant ( p < 0.05) differences in mercury content in other tissues were observed, which could not account for the marked sex- and age-related differences in renal mercury concentrations. Renal γ-GTP activity gradually increased in males with maturation, and a sexual dimorphism of renal γ-GTP was apparent after the fourth week. Seven days after castration of 4-week-old male mice, both renal mercury content and γ-GTP activity were decreased to the levels in females. Activity of γ-GTP was subsequently elevated to control male levels by sc injection of testosterone (5 mg/kg/day × 7 days). In female mice, both renal mercury content and γ-GTP activity were increased to the level of males by testosterone treatment (5 mg/kg/day × 14 days). Thus, the renal mercury content was closely correlated with changes in renal γ-GTP activity. These results suggest that sex and age differences in renal methylmercury accumulation may be due to a difference in renal γ-GTP activity controlled at least in part by testosterone.

Immunocytochemical localization of gamma-glutamyl transpeptidase in porcine ciliary epithelium

Our previous work on cultured bovine ciliary epithelial cells indicated that γ-glutamyl transpeptidase (GGTP) activity is primarily associated with the non-pigmented epithelial cells and is virtually absent in the pigmented epithelial cells [Ng and Shichi, (1987) J. Ocular Pharmacol, 3, 341–348]. We have now investigated the localization of GGTP in porcine ciliary processes by immunocytochemical methods using goat anti-rat GGTP serum detected by rabbit anti-goat IgG secondary antibodies conjugated to fluorescein isothiocyanate or horseradish peroxidase, or biotin-conjugated secondary antibodies and streptavidin (Auroprobe). The non-pigmented cells were labeled uniformly and intensely by fluorescent antibodies, while only the plasma membrane (on the stroma side) was labeled in the pigmented cells. Immunoperoxidase reactions demonstrated that only the plasma membrane was labeled also in non-pigmented cells. The apparent uniform labeling of the cytoplasm of non-pigmented cells by fluorescent antibodies was attributed to the extensively infolded plasma membrane. The peroxidase reaction product was not found in the mitochondria, nucleus or endoplasmic reticulum of non-pigmented or pigmented cells. Immunogold labeling indicated that antigenic sites are associated with the plasma membrane infoldings (vitreous side) of non-pigmented cells, and the plasma membrane (stroma side) of pigmented cells. For enzymatic localization of GGTP activity in ciliary epithelial cells, non-pigmented and pigmented epithelial cells were carefully separated from fresh porcine ciliary body and homogenized to isolate microsomal fractions containing vesicles of plasma membrane and endoplasmic reticulum. The specific activity of microsomes from non-pigmented cells was 23 times higher than that of microsomes from pigmented cells. We conclude that GGTP is localized to the plasma membrane of both non-pigmented and pigmented cells and that the markedly high GGTP activity of non-pigmented cells is due to massive plasma membrane infoldings.

Variations in the effects of l-methionine- dl-sulfoximine on the activity of cerebral γ-glutamyl transpeptidase in rats as a function of age

Changes in the activity of γ-glutamyl transpeptidase (GGTP) and the effects of a subacute dose (150 mg/kg b.wt.) of methionine sulfoximine (MSO) on its activity were studied in cerebral cortex, cerebellum and brainstem of rats of 4 different age groups. GGTP activity increased with increasing age between days 10 and 180 after birth and decreased between 180 and 360 days of age in these 3 regions of the brain. Older animals showed convulsions and succumbed to the toxic effects of MSO. In the younger animals, wobbly gait and splayed leggedness were noticed in the earlier time periods and these animals recovered from the toxic effects of the drug. Following the administration of MSO, GGTP activity was suppressed in all the regions (excepting the cerebral cortex and cerebellum of 90-day-old animals). In 10- and 90-day-old animals, there was a complete recovery of enzyme activity which exceeded the control value as the time progressed. No such recovery was observed in 180- and 360-days-old animals. Parallel changes were observed in the GGTP activity and the behavioural pattern of the animals. These results were discussed in relation to the localization of this enzyme in astrocytes and capillaries.

Glial cells and neurons induce blood-brain barrier related enzymes in cultured cerebral endothelial cells

The blood-brain barrier (BBB) in mammals is created and maintained by cerebral endothelial cells (cEC) that express specialized functional properties, including intercellular tight junctions, absence of fenestrae and specific membrane transport systems. It has been proposed that the differentiation of these characteristics, acquired during brain development, is controlled by the neural environment 15, 24. Co-culture experiments of cloned cEC with astroglial cells, C6 glioma cells and cortical neurons, with plasma membranes or conditioned media of these cells, were used to study induction of some BBB characteristics in vitro. Activities of Na +, K +-ATPase and γ-glutamyl transpeptidase (GGTP), an enzyme responsible for amino acid transport across the BBB, were taken as parameters for BBB function. Co-culture of cEC with C6 glioma cells caused a two-fold increase in GGTP activity and this activity was likewise amplified by incubation with plasma membrane fractions derived from C6 glioma cells, embryonic brain cells and cortical neurons; conditioned media (soluble factors) had no effect. Na +, K +-ATPase activity, estimated from the ouabain inhibitable fraction of 86Rb uptake, was increased by about 90% in cEC incubated with C6 glioma plasma membranes. We propose from these data that both neurons and glial cells confer BBB characteristics on cEC via cell-cell contact.

Gamma-glutamyl transpeptidase in milk and butter as an indicator of heat treatment

Abstract Naturally present γ-glutamyl transpeptidase (GGTP) in whole and skim milk was inactivated by heat treatment at >79°C for 16 s. Of the total activity in whole milk, 72% was found in the skim milk fraction. Little seasonal variation was noted in either whole or skim raw milk over a period of 300 days. Using a commercially available test kit for GGTP, as little as 0·1% raw milk or cream could be detected in pasteurized skim milk and butter. An alternative GGTP method examined was less sensitive than the commercial method. However, it was necessary for cream products with low GGTP activity since cream interfered with the commercial assay. No reactivation of GGTP was found in whole milk or butter under a variety of conditions. Commercial milk and cream samples were negative for GGTP activity. The results suggest that GGTP analysis could be useful for monitoring the heat-treatment give to fluid milk products.

An explanation for strain and sex differences in renal uptake of methylmercury in mice

The present investigation was designed to elucidate the mechanism for strain and sex differences in renal methylmercury accumulation, in five mouse strains, viz. BALB/cA, C57BL/6N, CBA/JN, C3H/HeN and ICR. Strain and sex comparisions of factors which influence renal mercury accumulation were made. Strain and sex differences were observed in renal mercury accumualation 4 h after methylmercuric chloride (MMC) (1μmol/kg, s.c.) injection. Glutathione (GSH) content in liver and kidney showed significant strain and sex differences. Pretreatment with 1,2-dicholor-4-nitrobenzene (DCNB), to deplete hepatic GSH without affecting renal non-protein thiol (NSH) level, led to a dose-dependent decrease in hepatic and plasma GSH concentrations that correlated with decreased mercury levels in the kidney 10 min after MMC (1 μmol/k, i.v.) injection. This indicates that hepatic and plasma GSH levels are related to mercury accumulation into the kidney. Renal γ-glutamyltranspeptidase (γ-GTP) activity significantly varied among the strains, and in BALB/cA and ICR, renal γ-GTP activity was about 2-fold higher than that in females. Renal γ-GTP activity was also correlated wit renal mercury content. These results suggest that strain and sex differences in renal accumulation of mercury are attributable to differences in tissue GSH content and possibly to differences in renal γ-GTP activity.

Assessment of the heat treatment of ice cream mixes by enzyme assay

Ice cream mixes containing varying levels of sweeteners were subjected to heat treatment at 6., 6°C for up to 30 minutes. The levels of y-glutamyl transpeptidase (GGTP) and the survival of streptococci were monitored. The reduction in GGTP activity was less than had been expected from earlier work. Neither GGTP activity nor survival of streptococci could be related statistically to water activity under the experimental conditions.

Hormonal and paracrine regulation of γ-glutamyl transpeptidase in rat Sertoli cells

The effects of follicle-stimulating hormone (FSH) and testosterone on Sertoli cell γ-glutamyl transpeptidase (γ-GTP) activity have been studied in vitro. Addition of FSH to Sertoli cell cultures for 5 days induced stimulation of γ-GTP activity. No testosterone effect was observed alone or in combination with different doses of FSH. Time course studies for a supramaximal dose of FSH showed that enzyme induction could be achieved after a 48 h stimulation. Furthermore, a gradual stimulation of γ-GTP activity in response to increasing numbers of germinal cells (GC) added in coculture, was observed. Stimulation was also demonstrated with germinal cell-conditioned medium (GCCM). Stimulatory effects of GC and GCCM were additive with those of FSH, suggesting that different mechanisms were involved.

Effects of prenatal alcohol on γ-glutamyl transpeptidase in various brain regions

Prenatal exposure of rats to alcohol produces morphological, biochemical, behavioral and physiological abnormalities. The enzyme γ-glutamyl transpeptidase activity is increased when an animal is exposed to alcohol chronically. We examined the effect of the in utero exposure to alcohol on the regional brain distribution of γ-GTP. Pregnant rats were placed into the following treatment groups: LC (ad lib lab chow and water), PF (pair-fed), 10% EDC (ethanol derived calories), 20% EDC and 35% EDC. The LC group was fed lab chow and water ad lib, the PF, 10% EDC, 20% EDC and 35% EDC groups were fed a liquid diet containing either 0%, 2%, 4% or 6.7% v/v ethanol, respectively. All the treatment groups received the same volume of an isocaloric diet as was consumed by the 35% EDC group. At birth, litters were culled to six and cross fostered to untreated surrogate mothers. Pups were sacrificed at 30 days of age and brains dissected into 8 regions. Each brain region was homogenized and divided into soluble and membrane bound fractions by centrifugation and digestion with deoxycholic acid. γ-GTP activity was then measured. It was determined that the in utero exposure to alcohol produces an increase in brain γ-GTP activity. The increase in γ-GTP activity in some areas of brain is maintained at least until the animals are 30 days old. Alcohol treatment had no effect on the activity associated with the soluble form of enzyme. However, the activity associated with the membrane bound form of the enzyme was increased in several brain regions. In the midbrain and hypothalamus the activity was increased in a dose-dependent manner. These animals may thus be better able to degrade and take up higher amounts of amino acids for glutathione synthesis.

Maternal tobacco smoking and changes in amino acid uptake by human placental villi: Induction of uptake systems, gammaglutamyltranspeptidase and membrane fluidity

Maternal smoking depressed the active uptake of amino acids by human placentae and lowered their levels in the placenta and umbilical vein. During starvation of cells for amino acids, more amino acid carriers are induced and incorporated into the plasma membrane. A question arises whether there could be similar changes due to maternal smoking in the placental amino acid uptake carrier systems. Therefore, the characteristics of (a) the uptake of 2-amino[1- 14C]-isobutyric acid (AIB) by isolated placental villi, (b) gammaglutamyltranspeptidase (GGTP), a critical enzyme of the gammaglutamyl cycle (GGC) for the uptake of amino acids in human placenta, and (c) lipid structural parameters (reciprocal of fluidity), by steady state fluorescence polarization of plasma membrane vesicles of microvilli (MV) and microsomal membranes (MM) of umbilical and chorionic plate arteries of placentae of smoking and non-smoking mothers were investigated. The above investigations gave the following results: 1. (a) Washed placental villi of smokers exhibited higher capacity for AIB uptake than those of non-smokers. The higher uptake capacity was mainly due to increase in V max for AIB uptake in smokers. K m increased for placental AIB uptake in smokers. 2. (b) Maternal smoking lowered GGTP activity of MV by decreasing its V max. Therefore, maternal smoking decreases the formation of gammaglutamyl-amino acid (GGAA) on the surface of trophoblast which are absorbed by the trophoblast. The degree of absorption of GGAA is considered as an inverse environmental signal for the cell to regulate amino acid transport systems. Maternal smoking seems to decrease the formation and absorption of GGAA and thereby induce the formation of new carriers for AIB uptake. 3. (c) Maternal smoking increased the values for lipid structural order parameters and microviscosity of MV and induced tolerance against fluidization by ethyl alcohol in MM of umbilical and chorionic arteries. The alterations could increase K m for AIB uptake system and decrease the sensitivity of umbilical and chorionic arteries to vasoconstrictive substances like 5-hydroxytryptamine and catecholamine which are released by nicotine. All these changes tend to overcome the deficits produced in placental amino acid transport and satisfy the demands of the growing fetus for amino acids.

経皮的腎切石術後急性期における尿中NAG,γ-GTP活性の変動

We performed percutaneous nephrolithotomy (PNL) on 49 patients between May, 1986 and March, 1987. To investigate acute renal damage from PNL, we measured urinary NAG (N-acetyl-beta-D-glucosaminidase) and gamma-GTP (gamma-glutamyl transpeptidase) activities before PNL and for 6 days after PNL in 24 patients. The NAG activities elevated beyond normal level in 23 patients and gamma-GTP activities in 15 patients. NAG activities showed a peak level in the third day after PNL and gamma-GTP activities in the next day of PNL. After the peak both enzyme activities got down gradually. There was no difference in NAG and gamma-GTP activities between nephrostomy and lithotripsy in 2 staged patients. And the intrapelvic pressure during operation was at the normal level in 5 patients. Therefore, we think that the cause of NAG and gamma-GTP activity elevation is a mechanical damage, not an influence of the irrigation fluid. Large stones, long operation time and 2 stage procedure were the factors that produced high enzyme activities, because, we guess, the frequency of mechanical damages to the kidney increase in such cases. Postoperative pyrexia caused a slight increase in enzyme activities but preoperative hydronephrosis exerted no influence on both enzyme activities. We also measured creatinine clearance before and after PNL but no significant change was obtained. PNL causes only slight mechanical damage to the operated kidney which is reversible when assessed by NAG and gamma-GTP activities and the glomerular function is not affected. Therefore, we conclude that PNL is a safe treatment for upper urinary tract stones.

Local anti‐inflammatory activity of steroid‐21‐oate esters in the carrageenan pleurisy model of acute inflammation

AbstractLocal anti‐inflammatory activities in the carrageenan (CGN)‐induced pleurisy model are reported for steroid‐21‐oate esters derived from prednisolone. Following administration of equipotent doses (per rat) of prednisolone (P),.5mg; methyl 17,20α‐acetonidodihydroprednisolonate (P4AC), 1 mg; methyl 20β‐dihydroprednisolonate (P4B), 1.3 mg; methyl 20α‐dihydroprednisolonate (P4A), 5.8 mg; and methyl 17,20β‐acetonidodihydroprednisolonate (P4BC), 6 mg, effects of the steroids on exudate volume, leukocyte recruitment, and enzyme levels of cell‐free exudates and washed exudate cells were assessed. All derivatives tested significantly inhibited emigration of neutrophils (PMNs) and monocytes (MNs). Steroid treatment with the β‐isomers reduced exudate volumes by 41% and 56% for P4B and P4BC, respectively. In 5 hr neutrophilic exudates, free β‐glucuronidase levels were reduced by 43% by either P4B or P4AC treatments. Of the derivatives tested P4B and P4AC treatments resulted in the greatest reduction of free lysozyme levels. Activities of membrane‐bound γ‐glutamyl‐transferase (GGTP) in exudate cell pellets were reduced following treatment with P and the 20 alpha‐epimers P4AC and P4A. Systemic effects assessed as decreases in plasma corticosterone or suppression of circulating lymphocytes were noted only following P treatment. These results suggest that 1) the locally active steroid‐21‐oate esters act at the site of inflammation by inhibiting PMN and MN infiltration in a manner congruous with conventional steroids, 2) steroid stereochemical configuration plays a role in effects on exudate volumes and GGTP activities, and 3) due to the absence of systemic effects, the steroid‐21‐oate esters may be safer local anti‐inflammatory agents.

Changes in alkaline phosphatase and .GAMMA.-glutamyl transpeptidase during the process of rat hepatocyte proliferation.

D-galactosamine was injected i. p. into rats at a single dose level of 250mg/kg. Basophilic hepatocytes and their mitotic forms were observed 48hr and 72hr after the administration of the amino sugar. At these stages, the biochemical activities of alkaline phosphatase (ALPase) and γ-glutamyl transpeptidase (γ-GTP) in rat liver homogenate increased significantly in comparison to those in the control rats.In the histochemical analysis, 48hr and 72hr after administration of the amino sugar, a high level of activity of both ALPase and γ-GTP was seen along the cell borders between adjacent hepatocytes and along the entire hepatocyte surface. At the level of electron microscopy, the reaction products showing ALPase activity were observed in abundance along the complex interdigitation of the plasma membranes, which were present on the cell borders between adjacent hepatocytes.

Relationship between serum .GAMMA.-glutamyl transpeptidase fraction pattern and the pattern of food intake.

The effects of the food intake pattern on the activity and fraction pattern of serum γ-glutamyl transpeptidase (γ-GTP) were examined in 257 healthy Japanese men.Applying the technique of factor analysis to the food intake data, the following three factors were extracted. The first factor (F1): meats, eggs, and vegetables had a highly positive factor loading. The second factor (F2): wheat had a highly positive factor loading, while rice had a highly negative factor loading. This factor was considered to be a “wheat versus rice factor”. The third factor (F3) could not be explained simply in terms of its factor. The scores of the first two factors for the 257 subjects were calculated.Significantly negative correlations were observed between the percentage of GT1 fraction and the factor score of F1 (r=-0.230, p<0.01), between the percentage of GT1 fraction and the factor score of F2 (r=-0.187, p<0.01). The total serum γ-GTP activity was not correlated with the factor score. These results suggested that the percentage of GT1 fraction is influenced by the pattern of food intake.

Use of an in vitro system to study the effects of lead on astrocyte-endothelial cell interactions: A model for studying toxic injury to the blood-brain barrier

We investigated the effect of inorganic lead on the interaction of immature rat astrocytes and bovine adrenal endothelial cells. The two cell types were cultured alone and in coculture in the presence or absence of lead acetate for up to 1 week. A battery of cell specific markers was used for cell identification. Newborn Sprague-Dawley rat brain astrocytes were more sensitive than bovine adrenal endothelial cells to the cytotoxic effects of 10–50 μ m lead acetate, as demonstrated by a decrease in cell number and by the presence of intracellular vacuoles and detached cells. The number of astrocytes decreased to 50% of control after 4 days in culture at a concentration of 10 μ m lead. In contrast, a mitogenic effect of lead was observed on the endothelial cells at this concentration, with an increase in cell number to 110% of control. In coculture, the two cell types demonstrated a distinctive cellular organization and the astrocytes were less sensitive to the cytotoxic effects of lead than when they were cultured alone. A lead-enhanced induction of a neural capillary enzyme activity, γ-GTP, was detected histochemically in the coculture system. These results are consistent with a maturing of differentiating effect of the endothelial cells on the astrocytes, making them less susceptible to lead and mature enough to induce γ-GTP activity in the endothelial cells.

Activity of gamma-glutamyl transpeptidase in the diagnosis of alcoholism

To diagnose alcoholism, mainly clinical methods of examination of patients are used. At the same time, more and more attention is paid to the development of biochemical tests in order to assess the disease more objectively. A number of studies have studied the effect of alcohol abuse on the activity of serum gamma-glutamyl transpeptidase (g-GTP). This enzyme is widely distributed in organs and tissues, which accounts for the lack of specificity of the test. Serum g-GTP activity has been shown to be elevated in all types of hepatobiliary disorders, including hepatitis, cirrhosis, congestion, metastasis, as well as in pancreatitis, chronic nephritis, etc. Hepatic gGTP is an enzyme sensitive to the effects of ethyl alcohol, and therefore can serve as an objective test for identifying alcohol abusers.

Glycylproline dipeptidyl aminopeptidase and γ-glutamyl transpeptidase in human hepatic cancer and embryonal tissues

Changes of glycylproline dipeptidyl aminopeptidase (GPDA) and γ-glutamyl transpeptidase (γ-GTP) activities and their subcellular distributions were compared in human hepatic cancer and embryonal tissues. The activity of GPDA in cancer tissues was significantly higher than that found in healthy liver, though there were no significant differences between fetal and adult livers. The placenta, however, had the highest GPDA activity. The activity of γ-GTP, on the other hand, was increased significantly not only in cancer tissues but also in live tissues adjacent to the tumor, and it was higher in the fetal liver but much lower in the placenta. Subcellular distribution of GPDA was also different from that of γ-GTP in cancer tissues, especially after postmortem changes. These results suggest the possibility that GPDA has carcinoembryonic characters similar to γ-GTP, but the mechanisms, whereby serum activities of these two enzymes were increased in hepatocellular carcinoma patients, are different from each other.

The effect of the host's age on the pathology of Eimeria stiedai infection in rabbits.

The pathology of experimental Eimeria stiedai infection in 2- and 4-month-old rabbits raised coccidia-free was studied. Over 50 days of infection, the serum activities of aspartate (AST) and alanine (ALT) aminotransferases, alkaline phosphatase (AP) and gamma-glutamyltranspeptidase (GGTP) were analyzed as indicators of hepatic lesions and total serum globulins with respect to the immune response of the host; parasite development was followed by oocyst output; weight gain, food intake and relative liver weight were analyzed to control the performance of infected animals. The age of the host strongly affected parasite development and consequently the biochemical and zootechnical parameters differed more markedly in the younger animals; however, the enzyme ALT showed an increase independent of parasite development, and infection did not affect GGTP activity. The increase in age was responsible for resistance of rabbits to hepatic coccidiosis and older animals were less affected than young ones.

各種疾患牛における血清γ-GTP値

Serum γ-GTP activity was tested in 119 cattle with various diseases to evaluate a diagnostic significance. An increase in γ-GTP activity corresponding to histological liver lesions was not affected with such traumatic muscle damage as that in downer cows. In the fatty liver serum γ-GTP activity was slower in response showing than serum GOT activity. T1/2 of BSP clearance was delayed to 15'40''±16'47'' in the case of increased γ-GTP activity (113.9±158.7mU/ml). As a result, the measurment of serum γ-GTP activity was considered to be useful for the examination of chronic liver lesions in cattle.

分離ヒト脳微小血管

We evaluated activities of 5'-nucleotidase (5'-N), 3'-5'-phosphodiesterase (3'-5'-PDE), AchE, and ChAT on intraparenchymal blood vessels of a human brain. Brain vessels were isolated using the method which we developed. Fragments of human brain weighed 2 or 3g were minced and passed through 250μm nylon mesh. The material on the mesh was resuspended in buffer, after mild homogenization, passed through 73μm mesh. The mesh was washed, then the fluid was passed through 150μm mesh. Two vessel fractions were separated on the mesh and in the filtrate. The fraction on the mesh consisted primarily of larger vessels greater than arterioles, and that in the filtrate consisted predominantly of microvessels, which were purified by passing through a column of glass beads and centrifuged on sucrose density gradient. We evaluated the degree of contamination of isolated vessels using cerebroside as an indicator. The cerebroside level in these fractions was less than 5 percent of that in the brain homogenate.The activity of γGTP was significantly higher than that in the brain homogenate. These results indicate that enzyme activities are preserved well during the isolation procedure. 5'-N level was significantly lower in these fractions. 3'-5'-PDE level was significantly higher in the large vessel than in the small vessel fraction. Changes of these enzyme activities in the vessels may affect micro-circulation and blood brain barrier function via change in the concentration of adenosine and cyclic AMP. ChAT activity was very low in vessel fractions. AchE activity was significantly higher in both vessel fractions than in the brain homogenate, and in small vessel fraction than in the large vessel fraction. The discrepancy of these two enzyme activities in isolated vessels will provide a new tool and scope in studies on brain microvessels.