Inhibition of cytosolic rat hepatic glutathione S-transferase activities by bromosulfophthaleins

Summary The enzymatically catalyzed conjugation of glutathione with 1-chloro-2,4-dinitrobenzene and styrene-7,8-oxide is inhibited by tetrabromosulfophthalein in a non-competetive way, although tetrabromosulfophthalein itself is a substrate for glutathione S-transferases. Dibromosulfophthalein, which is not a substrate for glutathione S-transferases, inhibits the 1-chloro-2,4-dinitrobenzene conjugation competetively and the styrene-7,8-oxide conjugation non-competetively.     

NMR structural studies of glutathione S-transferase

The use of nuclear magnetic resonance (NMR) spectroscopy for the structure determination of small proteins is now widely recognized; what is less frequently reported is the application of NMR techniques for high-resolution studies of large proteins (M _r larger than 30 kD). We demonstrate here how an integrated approach, using heteronuclear NMR and X-ray crystallography, can provide useful and biologically important information for large protein systems. The dynamic features of the human A1-1 glutathione S-tranferase and the role of the C-terminal region are being probed by NMR; in the X-ray crystal structure, the electron densities for this region of the protein are uninterpretable.     

Glutathione-related enzyme activities in pregnant rat liver

Summary The levels of GSH-related enzyme activities during pregnancy were determined. A significant increase in Selenium-dependent GSH peroxidase and GSH S-transferase E activity was observed. A concomitant increase in -glutamylcysteine synthetase was measured, which indicated an increased ability to synthesize the tripeptide.     

The effects of vitamin A nutritional status on glutathione,glutathione transferase and glutathione peroxidase activities in rat intestine

Summary In rat intestine, the glutathione level was increased, glutathione peroxidase activity decreased and glutathione-S-transferase unchanged by vitamin A deficiency.     

Effect of chronic ethanol treatment on peroxisomal acyl-CoA oxidase activity and lipid peroxidation in rat liver and heart

Summary Chronic ethanol administration was shown to increase catalase and acyl-CoA oxidase activities in rat myocardium but did not alter the activity of liver peroxisomal enzymes. As a result of alcohol consumption a 2–3-fold increase in the level of lipid peroxidation was observed in the heart tissue while in the liver the induction was much less pronounced.     

The chemistry and biology of inhibitors and pro-drugs targeted to glutathione S-transferases

The cytosolic glutathione S-transferases are a family of structurally homologous enzymes with multiple functions, including xenobiotic detoxification, clearance of oxidative stress products, and modulation of cell proliferation and apoptosis signaling pathways. This wideranging functional repertoire leads to several possible therapeutic uses for isoform-specific GST inhibitors. These inhibitors may be used, in principle, to modulate tumor cell drug resistance, as sensitizers to therapeutically directed oxidative stress, to enhance cell proliferation and to augment anti-malarial drugs. With increasing knowledge of GST structural and function, rational design strategies and mechanism-based inhibitors have been exploited successfully. However, design of isoform specificity remains a significant challenge in GST inhibitor development. Strategies for further inhibitor design and their possible limitations, along with potential therapeutic uses, are summarized.Received 24 November 2004; received after revision 12 January 2005; accepted 11 February 2005     

Comparison of lysine and tryptophan catabolizing enzymes in rat and bovine tissues

Summary Earlier studies indicate that -aminoadipate aminotransferase (AadAT) and kynurenine aminotransferase (KAT) activities from rat tissues are associated with a single protein. However, our recent studies indicate that AadAT activity from bovine liver and kidney is not associated with KAT activity. To test whether the lysine and tryptophan catabolism in bovine tissues differ from that in rat tissues, we compared the activities of enzymes involved in lysine and tryptophan pathways in rat and bovine tissues. The activities of lysine catabolizing enzymes such as AadAT, lysine -ketoglutarate reductase and saccharopine dehydrogenase in the bovine tissues were significantly lower than those found in rat tissues. The activities of tryptophan catabolizing enzymes such as KAT and kynurenine hydroxylase in the bovine tissues were negligible as compared to those in rat tissues. The results suggest that lysine is degraded via the saccharopine pathway in the livers and kidneys of both species but the metabolism of tryptophan in bovine tissues may be different from that in rat tissues.Acknowledgments. This work was supported by a grant from the Children's Hospital of Michigan and by a Research Career Development Award from the National Institutes of Health to D. R. Deshmukh.     

The effects of vitamin A nutritional status on glutathione levels and microsomal lipid peroxidation in rat lung

Summary In vitamin A-deficient rats, the glutathione level in lung was diminished and microsomal lipid peroxidation much increased. In vitamin A-loaded animals, however, both were depressed below control. Thus vitamin A protection against lipid peroxidation is independent of glutathione.Acknowledgments. We thank Dr L. Y. Y. Fong and Mr David Y. H. Woo for preparing the animals used in this research, for retinol determinations and for valuable discussions, and also the China Medical Board of New York and the University of Hong Kong for the award of a Fellowship to V.P.     

Inhibition of phosphoenolpyruvate carboxykinase by 6-phosphogluconate in rat liver

Summary Various concentrations of 6-phosphogluconate inhibit rat liver phosphoenolpyruvate carboxykinase activity. 0.04 mM 6-phosphogluconate, which is the concentration found in vivo, caused a 50% inhibition of 6-phosphoenolpyruvate carboxykinase activity. 6-Phosphogluconate lowered the V_max of the enzyme and increased the concentration of phosphoenolpyruvate required to achieve one-half of the maximum velocity. The role of 6-phosphogluconate as a regulator of the coordination of fluxes through three metabolic pathways is discussed.     

Acute60Co-gamma irradiation of rats decreases the inhibitory effect of succinate on the lipid peroxidation of liver mitochondria

Summary Succinate inhibits NADPH-dependent lipid peroxidation of liver mitochondria. This effect of succinate decreased 12 h after whole-body⁶⁰Co-gamma irradiation, depending on the dose of irradiation.     

Development and hormonal control of thioredoxin and the thioredoxin-reductase system in the rat liver during the perinatal period

Summary The development and hormonal regulation of thioredoxin and of the thioredoxin-reductase system were investigated during the perinatal period in rat liver. An immunological procedure was developed in order to quantify thioredoxin in fetal and neonatal hepatocytes. Both immunoreactive thioredoxin and thioredoxin-reductase activity appeared on day 16.5 of pregnancy. The level of immunoreactive thioredoxin increased during the late fetal period, and its level was the same 24 h after birth. Moreover, its development was not subjected to hormonal regulation by corticosteroids and glucagon. In contrast, thioredoxin-reductase activity increased 3 times during the late fetal period and presented a marked increase 24 h after birth. In the absence of glucocorticoids there was no increase in the level of thioredoxin reductase, while administration of hydrocortisone acetate and glucagon to fetuses prematurely evoked its activity. This study suggests that if thioredoxin acts physiologically, this activity is related to the state of reduction of the molecule rather than to the total concentration in the liver.     

Effects of female sex hormones on polyamine-oxidizing enzyme activities and polyamine concentrations in immature rat uterus and liver

17-estradiol (E₂) and progesterone (P) treatment of immature female rats (10 g/100 g body weight) respectively resulted in 1.38-fold (p<0.02) and 1.42-fold (p<0.02) increase in the uterine polyamine oxidase activity, and 2.45-fold (p<0.001) and 1.43-fold (p<0.02) increase in the uterine diamine oxidase activity, as compared to the controls. E₂ caused a 5-fold (p<0.05) and a 1.36-fold (p<0.05) increase in putrescine and spermidine concentration respectively in rat uterus. Increases of 1.7-fold (p<0.02) and 1.6-fold (p<0.05) in putrescine and spermine concentration were determined in the P-treated uterus, as compared to the controls. The spermidine/spermine ratio, which is regarded as an index of growth rate, was higher in the E₂-treated uterus and lower in the P-treated uterus than in the control uterus. No statistically significant hormonal effects were estimated in the immature liver. The data reported suggest the possibility of an involvement of polyamine-oxidizing enzymes in the modulation of polyamine concentrations in rat uterus by the female sex hormones.     

Effects of chronic caffeine feeding on the activities of oxygen free radical defense enzymes in the growing rat heart and liver

The purpose of the present study was to determine the relationship between concentration of Zn, Cu and Fe, and the catalase, glutathione peroxidase and superoxide dismutase activities in the heart and liver of newborn rats whose dams were fed a diet supplemented with caffeine. Heart Zn levels of the 22- and 30-day-old rats of the caffeine group showed a decrease, whereas liver Zn levels showed an increase compared to the control. Cu levels in the liver at day 22 in the caffeine group were less than in the control. Cu- and Zn-containing superoxide dismutase activities showed an increase in the hearts of the caffeine group compared to the control. The activity of catalase and glutathion peroxidase showed no difference in the heart and liver between the groups. The present study suggests the possible involvement of superoxide dismutase enzyme in the impairment of heart formation as a result of chronic caffeine intake in the early growing period.     

Changes of the level of proteinase inhibitors in rat plasma during turpentine-induced inflammation

Summary The levels of rat plasma -macroglobulins, -cysteine proteinase inhibitor, haptoglobin and antipapain activity were studied during the acute-phase reaction after an injection of -pinen. An increase in concentration of all the compounds examined was observed.     

Oyster mushroom (Pleurotus ostreatus) reduces the activity of 3-hydroxy-3-methylglutaryl CoA reductase in rat liver microsomes

The effect of dried oyster mushroom (Pleurotus ostreatus) on cholesterol (C) content in serum, in lipoproteins and in liver, and on the activity of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase in liver microsomes, was studied in male rats (strain Wistar, initial body weight 75 g) fed on low-cholesterol (9 mg/100 g) and high-cholesterol (0.3%) diets. Addition of 5% oyster mushroom to both diets reduced significantly the C-content in serum (by 30%), in very-low- and low-density lipoproteins (in a 11 ratio to the decrease of total serum C) and in liver (by 50%), as well as the activity of HMG-CoA reductase (by more than 30%).