Decreased glutathione content of human erythrocytes produced by methyl phenylazoformate

Reduced nicotinamide adenine dinucleotide and the reduction of oxidized glutathione in human erythrocytes

The ability of reduced nicotinamide adenine dinucleotide (NADH), generated through the activity of lactic acid dehydrogenase, to support the reduction of endogenous oxidized glutathione in intact human erythrocytes and in hemolysates was investigated. Rapid initial oxidation of endogenous reduced glutathione was effected with methyl phenylazoformate. Freshly obtained normal erythrocytes and erythrocytes deficient in glucose-6-phosphate dehydrogenase activity were unable to regenerate reduced glutathione upon incubation with lactate. Only normal erythrocytes were capable of reducing oxidized glutathione after preincubation with glucose, inosine, or a medium which promoted the synthesis of increased amounts of intracellular NAD. This regeneration of reduced glutathione could be explained by the generation of reduced nicotinamide adenine dinucleotide phosphate through the metabolism of accumulated phosphorylated intermediates of glycolysis. Hemolysates prepared from both normal erythrocytes and from erythrocytes deficient in glucose-6-phosphate dehydrogenase activity were able to reduce oxidized glutathione in the presence of added lactate and NAD. The results obtained indicated either an inability of the intact erythrocyte to utilize the NAD at the concentrations attained or an altered behavior of the system for the regeneration of reduced glutathione after lysis of the cell.

The lung as a generator of prostacyclin

Under physiological conditions prostacyclin is the main metabolite of arachidonic acid that is generated and released by the lungs. In man and in cat prostacyclin seems to be a circulating hormone whose concentration is 100-200 pg ml-1 higher in arterial blood than in mixed venous blood. Generation of prostacyclin by lungs can be increased by angiotensin II, bradykinin and arachidonic acid provided that low concentrations of these substances are infused into the pulmonary artery. Air pulmonary emboli and mechanical hyperventilation stimulate the lungs to generate more prostacyclin. Respiratory stimulants such as lobeline or almitrine are also effective prostacyclin releasers from the lung. It is proposed that this para-endocrine function of the lung protects coronary and cerebral arteries against thrombosis and atherosclerosis while pharmacological amplification of the pulmonary release of prostacyclin may constitute a new means of treating thromboembolic diseases.

Effects of ATP level on glutathione regeneration in rabbit and guinea-pig erythrocytes

1. Effects of ATP level on GSH regeneration were studied in the rabbit and guinea-pig erythrocytes. 2. There was a species difference in the efficacy of adenine, inosine and glucose as substrates for ATP recovery in the erythrocytes. 3. Erythrocytes GSH regeneration rate was found to be dependent on the cellular level of ATP in both the species.

Reduction of Cupric Ions with Elemental Sulfur by Thiobacillus ferrooxidans

In anaerobic or aerobic conditions in the presence of 5 mM sodium cyanide, an inhibitor of iron oxidase, cupric ion (Cu 2+ ) was reduced enzymatically with elemental sulfur (S 0 ) by washed intact cells of Thiobacillus ferrooxidans AP19-3 to give cuprous ion (Cu + ). The rate of Cu 2+ reduction was proportional to the concentrations of S 0 and Cu 2+ added to the reaction mixture. The pH optimum for the cupric ion-reducing system was 5.0, and the activity was completely destroyed by 10-min incubation of cells at 70°C. The activity of Cu 2+ reduction with S 0 by this strain was strongly inhibited by inhibitors of hydrogen sulfide: ferric ion oxidoreductase (SFORase), such as α,α′-dipyridyl, 4,5-dihydroxy- m -benzene disulfonic acid disodium salts, and diazine dicarboxylic acid bis-( N, N -dimethylamide). A SFORase purified from this strain, which catalyzes oxidation of both hydrogen sulfide and S 0 with Fe 3+ or Mo 6+ as an electron acceptor in the presence of glutathione, catalyzed a reduction of Cu 2+ by S 0 , and the Michaelis constant of SFORase for Cu 2+ was 7.2 mM, indicating that a SFORase catalyzes the reduction of not only Fe 3+ and Mo 6+ but also Cu 2+ .

The effect of Alcide, a new antimicrobial drug, on rat blood glutathione and erythrocyte osmotic fragility, in vitro

Alcide is an antimicrobial drug which has been demonstrated to kill a variety of common pathogenic bacteria as well as fungi, in vitro. This agent is supplied in liquid and gel forms and consists of two parts, one of which contains sodium chlorite, while the other contains lactic acid as the active ingredients. Mixing of the two parts prior to use produces chlorine dioxide (ClO2), a strong oxidizing agent. A dose-dependent decrease in glutathione content and erythrocyte osmotic fragility occurred after incubation of whole blood with Alcide. Glutathione concentration and erythrocyte osmotic fragility approached the control values after 240 min of incubation with Alcide containing 1 mM NaClO2. The addition of exogenous glutathione (50 mg 100 ml-1) or glutathione reductase and NADPH to rat blood in the presence of Alcide returned erythrocyte osmotic fragility to control values. Treatment of rat blood with Alcide did not change glutathione reductase or glutathione peroxidase activities after 1 h of incubation.

Useful agents for the study of glutathione metabolism in erythroyctes. Organic hydroperoxides

t-Butyl hydroperoxide and cumene hydroperoxide, both known to be substrates for glutathione peroxidase, were used to oxidize erythrocyte GSH. Addition of concentrations of hydroperoxides equimolar with respect to GSH in the erythrocytes or whole blood quantitatively oxidizes GSH in the erythrocytes with a half-time of 4.5s at 37 degrees C and about three times as long at 4 degrees C. In the presence of glucose, normal erythrocytes regenerate all the GSH in about 25min. However, glucose 6-phosphate dehydrogenase-deficient erythrocytes failed to regenerate GSH. Treatment of erythrocytes with hydroperoxides does not affect erythrocyte survival in rabbits. Oxidation of erythrocyte GSH with equimolar concentrations of hydroperoxides does not lead to formation of mixed disulphides of haemoglobin and GSH. The hydroperoxides do not affect erythrocyte glycolytic and hexose monophosphate-shunt-pathway enzymes. Previous studies on transport of GSSG from erythrocytes were confirmed by using t-butyl hydroperoxide to oxidize erythrocyte GSH.

Glutathione metabolism of the erythrocyte. The enzymic cleavage of glutathione-haemoglobin preparations by glutathione reductase

A complex of haemoglobin and GSH was prepared by incubating haemoglobin with GSH and acetylphenylhydrazine. GSH could be released from the crude preparation by incubation with NADPH. However, when the haemoglobin preparation was separated from glutathione reductase by DEAE-Sephadex chromatography, NADPH no longer released GSH. Rather, the addition of a combination of either partially purified human erythrocyte or crystalline glutathione reductase and NADPH was required to release GSH from the haemoglobin-GSH complex. This complex is commonly believed to represent a mixed disulphide of GSH and the cysteine-beta-93 thiol group. This interpretation was supported by the finding that prior alkylation of available haemoglobin thiol groups prevented the formation of the complex. By using haemoglobin-[(35)S]GSH complex as a substrate, it was shown that GSH itself released the radioactivity from the complex only very slowly. In contrast, the release of [(35)S]GSH was very rapid in the presence of NADPH and glutathione reductase. This suggests that the cleavage of the haemoglobin-GSH complex is not mediated by GSH with cyclic reduction of GSSG formed, but rather proceeds enzymically through glutathione reductase.

Effect of the thiol-oxidizing agent diamide on the growth of Escherichia coli

Oxidation of glutathione within Escherichia coli cells by diamide, (CH(3))(2)NCON=NCON(CH(3))(2), stops growth but does not cause cell death. Normal growth rates are resumed after periods which vary in length according to the diamide concentration. Consumption of excess reagent with added glutathione quickly reverses the inhibition. Another thiol-oxidizing agent, azoester, C(6)H(5)N=NCOOCH(3), causes lysis.