GAMMA-GLUTAMYL-TRANSFERASE ACTIVITY IN HUMAN PLATELETS - QUANTIFICATION OF ACTIVITY, ISOENZYME CHARACTERIZATION AND POTENTIAL CLINICAL RELEVANCE

Gamma-glutamyltransferase (GGT) activity in human platelet sonicates was 13.6 u/g of protein (range: 7.9-25.0) in 13 healthy, non-smoking, female volunteers; corresponding values in 16 males were: 20.3 (10.1-26.0), These values differed significantly (p = 0.034). Platelet and serum GGT activity correlated significantly (p < 0.04). Platelets seem to contain only the isoenzyme GGT 4, Part of this enzyme activity is in the form of aggregates or linked with membranes/proteins. This activity is released by Triton X-100 and trypsin and migrates as GGT 4, Serum GGT activity, a measurement in routine use, could be influenced by GGT released by platelets, It is therefore of interest that serum GGT activity can be increased in clinical conditions (e,g, myocardial infarction, diabetes, peripheral vascular disease) associated with platelet hyperactivity, Platelet GGT may influence intracellular S-nitrosoglutathione (a putative nitric oxide donor) levels, Potential associations between serum GGT activity and platelet function indices deserve investigation

Effect of exogenous melatonin on ethanol-induced changes in Na+,K+- and Ca2+-ATPase activities in rat synaptosomes

In the present study, the effects of acute ethanol ( EtOH) toxicity and of exogenous melatonin (MLT) on this toxicity were examined by measuring membrane-bound ATPases and acetylcholinesterase activities in rat synaptosomal membranes. The concentrations of plasma alpha-tocopherol and adrenal ascorbic acid (AA) were also measured. Synaptosomal Na+, K+- ATPase and Ca2+-ATPase activities were significantly depressed in acute EtOH-intoxicated rats compared with controls, while acetylcholinesterase activity remained unaltered. Pretreatment with MLT (10 mg/kg) prior to acute EtOH administration prevented EtOH-induced inhibition of ATPases. Adrenal AA and plasma alpha-tocopherol levels were also depressed regardless of MLT pretreatment. MLT treatment alone affected neither membrane-bound enzyme activities nor tissue and blood levels of vitamins C and E. It is concluded that acute EtOH intoxication disturbs neural transport functions through the membrane-bound ATPase activity depression. Reduced AA and alpha-tocopherol levels may contribute to the neurodegenerative effects of EtOH. However, pretreatment with a high dose of MLT before EtOH administration may be beneficial to prevent EtOH-induced toxicity on ATPase-mediated neural transport functions

Variations in serum cholinesterase activity in different age and sex groups

Measurements of serum cholinesterase activity has been used to assess liver function, predict susceptibility to prolonged apnoea after administration of the muscle relaxant succinylcholine and monitor excessive exposure to the anti-cholinesterase organophosphorus insecticides (1, 2). Serum cholinesterase activity can be affected by many physiological and pathological conditions such as age, pregnancy, puerperium, obesity, some drug therapy, and liver diseases. Additionally, congenital cholinesterase deficiency, which is due to several genetic variants of the enzyme, has also been reported (3, 4). Since the enzyme activity is altered by many factors, we aimed to show the distribution of serum cholinesterase activity levels in different age and sex groups, in order to establish the reference limits in our population

THE PRESENCE OF PROLIDASE ACTIVITY IN AMNIOTIC-FLUID AND ITS EVALUATION AS A MATURITY TEST

Prolidase (EC: 3.4.13.9) catalyses the hydrolysis of the peptide bond involving the imino nitrogen of proline or hydroxyproline. Because of the high proportion of imino acids in collagen, this enzyme plays an important role in its degradation. Since collagen turnover rate is expected to be high during fetal growth, the level of prolidase activity may reflect the degree of fetal maturation. In this study, amniotic fluid prolidase I activity was measured in term and preterm pregnancies. Lecithin concentration, which has been widely used for predicting fetal lung maturity, was also measured. Prolidase I activity was positively correlated with lecithin levels (n = 30; r = 0.42; p < 0.02), and also with birth weight of the babies (n = 30; r = 0.52; p < 0.01) in the term-mature group. Dysmature babies had significantly lower prolidase I activity in the amniotic fluid which was thought to be indicative of growth retardation

The effects of fluorides and/or trace elements on the solubilities of enamel and cementum

The purpose of this study is to determine the effects of fluorides and trace elements applied alone or in combination at different concentrations on the solubilities of enamel and cementum surfaces of the same teeth. The study has been performed on enamel and cementum surfaces of the impacted third molars extracted by surgical operation. Aqueous solutions of sodium fluoride, aluminum potassium phosphate, strontium chloride and titanium tetrachloride at different concentrations were applied to the surfaces. The solubilities of enamel and cementum and the depth of etchings have been calculated by means of the inorganic phosphorus in these etching solutions. According to the results, higher concentrations of fluoride and lower concentrations of strontium and titanium led to a significant reduction into solubilities of enamel and cementum. As certain combined applications of fluorides and trace elements decreased both of the enamel and cementum solubilities, it may be assumed that if such a treatment is beneficial during the adolescence of an individual, it may also be used when he is older

Prolidase I activity in liver tissue: Effects of ethanol and selenium

Selenium is an important factor as a component of glutathione peroxidase. In circumstances like chronic alcoholism, involving increased activity of free radicals, selenium deficiency can augment tissue degeneration by enhancing lipid peroxidation. In the present study, selenium was given to rats fed an alcohol-rich diet and the extent of liver injury was assessed by measuring prolidase I activity as well as hydroxyproline and free proline levels in the liver tissue after five months of ethanol ingestion. These findings were compared with the levels in controls and in the rats receiving sodium selenite in addition to ethanol. Hepatic prolidase activity increased in both groups receiving alcohol. There was no change in tissue hydroxyproline levels. We conclude that tissue (or serum) prolidase I activity may be useful for the early detection of alcoholic liver injury or other forms of oxidant-induced liver damage

Acute effects of estradiol and of diethylstilbestrol: Pro- or antioxidant potential?

This study was aimed to examine the effects of a single high dose of natural and synthetic estrogens on the antioxidant defense enzymes in liver and blood. Female Wistar albino rats, four to six months old, were divided into three groups, and received either i.p. injections of diethylstilbestrol (DES; 150 mg kg(-1) b.w.) or s.c. injections of estradiol (E-2; 25 mg kg(-1) b.w.), and the third group (control) was injected the solvent. Animals were killed under light ether anesthesia three hours after injection. Cu-Zn superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (Cat) enzyme activities and fluorometric malondialdehyde (MDA) determination were performed in liver tissue homogenates and in blood. Acute estradiol injection caused a significant increase in both MDA levels and GPx activity in liver tissue when compared to the controls, (p < 0.05 and p < 0.02; respectively). Changes in both enzyme activities and MDA concentration were unremarkable following acute DES injection. In blood, only Cu-Zn SOD activity was significantly altered in blood following E-2 injection. Although the significance of alteration in GPx activity remains unclear, it is most likely related to enhanced generation of lipoperoxides. A significant increase in MDA concentrations in liver tissue is indicative of pro-oxidative damage rather than an antioxidant action by E-2

Changes in enzymatic antioxidant defense system in blood and endometrial tissues of women after menopause

The effects of menopause on antioxidant enzyme activities were investigated in blood and endometrial tissues of women. Endometrial pieces were obtained from pre-or postmenopausal patients who had hysterectomy due to descendus or prolapsus uteri. In endometrium homogenates, both cytosolic superoxide dismutase (CuZn-SOD) and catalase (CAT) activities were similar in pre-or postmenopausal women (median ages 41 and 64, respectively); whereas GPx (glutathione peroxidase) activity was significantly decreased (p< 0.001). Activity of these enzymes were also compared in the blood of premenopausal and late menopausal women, and only GPx activity was found significantly low (p< 0.01). Subsequent measurements were carried out in blood of healthy menopausal women who were in the same age intervals with the premenopausal subjects studied, and GPx activity was found indifferent in two groups, indicating that the decrement is due to aging rather than the change in hormonal status. CuZn-SOD activity was highest in blood of late menopausal group compared with those in both premenopausal and early menopausal group, giving a significant difference with the latter (p< 0.001). In other words, SOD activity was increased in menopausal women at an older age, showing a diverse change with GPx activity