Glutathione reductase: stimulation in normal subjects by riboflavin supplementation

Glutathione reductase of hemolyzates from clinically normal subjects is activated by the addition of flavin-adenine dinucleotide. One-half maximum stimulation could be achieved by approximately 0.02 micromolar flavin-adenine dinucleotide; prior addition of adenosine triphosphate, adenosine diphosphate, or adenosine mnonophosphate prevented activation. Stimulation of glutathione reductase activity of red cells of normal subjects occurred when they were given 5 milligrams of riboflavin daily for 8 days. The degree of stimulation in vitro by flavin-adenine dinucleotide and in vivo by riboflavin was inversely proportional to dietary intake of riboflavin. The variety of clinical disorders which have been associated with glutathione reductase deficiency may have, as a common denominator, abnormalities in flavin-adenine dinucleotide formation.

Some effects of chlorambucil on enzymes of glutathione metabolism in drug-sensitive and -resistant strains of the Yoshida ascites sarcoma

1. Yoshida ascites cells from a strain sensitive to chemotherapy with alkylating agents contained elevated activities of the two enzymes directly responsible for glutathione synthesis, in comparison with a resistant cell strain. The activities of the glutathione-degrading enzyme gamma-glutamyltranspeptidase were comparable in both cell strains. 2. After parenteral administration of chlorambucil to rats carrying either strain of tumour, the activities of the glutathione-synthetic enzymes increased in the sensitive cells, but remained unchanged in the resistant cells. Drug treatment was without effect on the gamma-glutamyltranspeptidase activity of either cell strain. 3. The activities of a number of enzymes concerned in the oxidoreduction of glutathione remained unchanged after the administration of chlorambucil to rats carrying either strain of cells.

Hereditary nonspherocytic hemolytic disease associated with an altered phospholipid composition of the erythrocytes

A hemolytic disorder with mild hyperbilirubinemia and reticulocytosis of 6 to 15% was documented in eight members of a large family from the Dominican Republic and was presumed to be present in eight other members. The disorder appeared to be inherited as an autosomal dominant characteristic. Analysis of phospholipids by quantitative thinlayer chromatography revealed a distinct increase in phosphatidyl choline (lecithin) to 35.5 +/- SD 1.3% of the total (normal: 28.2 +/- 1.4%) in erythrocytes of affected members of the family, but not in the cells of unaffected relatives. The alteration appeared to constitute an absolute increase in lecithin content, rather than a decrease in other phospholipids. Erythrocytes from patients with other varieties of hereditary hemolytic disorders and comparable levels of reticulocytosis had normal phospholipid compositions. Plasma lipids of six affected members of the family were not unusual with respect to total lipid weight, total phospholipid, and cholesterol. Three patients with liver disease and jaundice were found to have marked increases in the lecithin content of the erythrocytes, but they also had extremely high plasma levels of total lipid, phospholipids, and cholesterol. Osmotic fragility of the erythrocytes of affected patients was decreased and the increase in fragility after incubation for 24 hr was less than that observed with normal erythrocytes. Autohemolysis after 48 hr was slightly increased and was corrected to nearly normal by the addition of glucose. The activities of 15 enzymes of the erythrocytes of the propositus were normal or elevated and the adenosine triphosphate content was normal. An abnormal hemoglobin could not be demonstrated. The life span of isologous erythrocytes in the propositus was reduced, but homologous erythrocytes survived normally.A causal relationship between the altered phospholipid composition and the hemolytic disorder has not been established.

Determination of glutathione reductase activity in microgram samples of tissue, quantitative histologic distribution of the enzyme in the rat adrenal and effect of adrenocorticotropin

A fluorometric method for determination of glutathione reductase activity in microgram samples of tissue, i.e., microtome sections, based on measurement of the decrease of reduced nicotinamide adenine dinucleotide phosphate due to its oxidation on reaction with oxidized glutathione, was developed and applied to the quantitative histologic distribution of the enzyme in the adrenal gland of the rat. Single subcutaneous injections of adrenocorticotropin in saline solution (25 mg/kg) produced little change of enzyme activity in any of the histologic zones, although there was some tendency for the peak activity to shift from fasciculata to the fascicular-reticular border region. The possible interrelationship of glutathione reductase with ascorbic acid and reduced nicotinamide adenine dinucleotide phosphate in adrenal function was considered.

The reactivity of the disulphide bonds of purified proteins in relationship to primary structure

1. With the aid of a coupled system involving glutathione reductase, the reaction of glutathione with the disulphide bonds of purified proteins has been studied. 2. Bovine serum albumin, conalbumin, lysozyme, trypsin inhibitors from egg white, lima bean and soya bean either did not react with glutathione or reacted only slightly. With these proteins reactivity was markedly increased by limited proteolysis. 3. Bovine and human gamma-globulins, fibrinogen and beta-lactoglobulin exhibited some reactivity (less than 15%) with glutathione and again this was increased by limited proteolysis. Pepsin, trypsin and chymotrypsin exhibited greater reactivity than the proteins previously mentioned. Di-isopropylphosphoryl-chymotrypsin exhibited less reactivity than chymotrypsin, suggesting that autolysis under the experimental conditions used contributed towards the reactivity of this protein. Proteolysis also increased the reactivity of these proteins. The three disulphide bonds of insulin were reduced by glutathione. 4. Above 35 degrees the disulphide bonds of serum albumin show a progressive increase in reactivity and at 55 degrees half of the bonds become accessible to glutathione. 5. From the results obtained with the proteins investigated, the conclusion reached is that the disulphide bonds of native proteins are structurally protected and do not react with glutathione under physiological conditions.

Cytochemical demonstration of glutathione reductase (EC 1.6.4.2) in Saccharomyces cerevisiae

A method for the cytochemical demonstration of glutathione reductase in unfixed yeast cells ( Saccharomyces cerevisiae) is described using reduced glutathione as substrate, nicotinamide adenine dinucleotide phosphate (nicotinamide adenine dinucleotide) as coenzyme and nitro blue tetrazolium as indicator. An essential prerequisite is an exactly controlled pH level (pH 6.5) of the complete incubation medium.

Studies on the oxidation-reduction systems of the erythrocyte

1. Starvation for 3 days produces a decrease in methaemoglobin-reductase and glutathione-reductase activities, but it does not alter the glucose 6-phosphate-dehydrogenase activity of the rat erythrocyte. 2. The feeding of a protein-free diet for 11 days causes greater changes in the first two enzymes and also a diminution of the third. Under this experimental condition slight decreases in protein and haemoglobin contents were noted. 3. The experimental animals did not show methaemoglobinaemia, probably because the activity of methaemoglobin diaphorase is preserved. 4. The GSH content was not affected but the stability of the tripeptide in the presence of an oxidizing agent was diminished.