Levels of glutathione, glutathione reductase and glutathione S-transferase activities in rat lung and liver.

The glutathione S-transferases (GST) represent a major group of detoxification enzymes. All eukaryotic species possess multiple cytosolic and membrane-bound GST isoenzymes, each of which displays distinct catalytic as well as noncatalytic binding properties: the cytosolic enzymes are encoded by at least five distantly related gene families (designated class alpha, mu, pi, sigma, and theta GST), whereas the membrane-bound enzymes, microsomal GST and leukotriene C, synthetase, are encoded by single genes and both have arisen separately from the soluble GST. Evidence suggests that the level of expression of GST is a crucial factor in determining the sensitivity of cells to a broad spectrum of toxic chemicals. In this article the biochemical functions of GST are described to show how individual isoenzymes contribute to resistance to carcinogens, antitumor drugs, environmental pollutants, and products of oxidative stress.A description of the mechanisms of transcriptional and posttranscriptional regulat...

The glutathione S-transferase supergene family: regulation of GST and the contribution of the isoenzymes to cancer chemoprotection and drug resistance.

In this review, we have examined the biochemical and toxic responses produced by halogenated aromatic hydrocarbons and have tried to develop a model for their mechanism of action. These compounds bind to a cellular receptor and evoke a sustained pleiotropic response. In many tissues this response consists of the expression of a battery of enzymes which are, for the most part, involved in drug metabolism, but in other tissues, those which develop toxicity, an additional set of genes is expressed which effects cellular involution, division, and/or differentiation. The toxicity of these compounds appears to be due to the sustained expression of a normal cellular regulatory system, of which we were previously unaware. In future investigations it is hoped that we will learn the nature and physiologic role of this regulatory system. Only then can we hope to understand the mechanism of toxicity of these compounds.

2,3,7,8-Tetrachlorodibenzo-p-Dioxin and Related Halogenated Aromatic Hydrocarbons: Examination of the Mechanism of Toxicity

Publisher Summary This chapter provides the spectrophotometric, titrimetric, nitrite, and cyanide assay for the differentiation of glutathione S-transferases. Spectrophotometric assays depend upon a direct change in the absorbance of the substrate when it is conjugated with glutathione (GSH). Because each of the reactions is catalyzed at a finite rate in the absence of enzyme, care is needed to reduce nonenzymatic catalysis by minimizing substrate concentrations and by decreasing pH wherever necessary. Titrimetric assay is based on the principle that the conjugation of alkyl halides with GSH can be measured titrimetrically. Although acid production accompanies many of the transferase catalyzed reactions in which thioethers are formed, titrimetry is only used when more convenient assays are not available. Nitrite assay is based on the principle that nitrite is released when GSH reacts with nitroalkanes or with organic nitrate esters. The nitrite can be assayed as the limiting factor in a diazotization reaction with sulfanilamide that produces a readily quantitatable pink dye. Cyanide assay is based on the fact that when glutathione transferases catalyze the attack of the glutathione thiolate ion on the electrophilic sulfur atom of several organic thiocyanates, it results in the formation of an asymmetric glutathionyl disulfide and cyanide. Cyanide can be readily quantitated by a calorimetric method.

Assays for differentiation of glutathione S-transferases.

Glutathione metabolism and its selective modification.

Hepatic side-chain oxidation of hexobarbital was estimated in rats before, during, and after administration of sodium phenobarbital in increasing dosage for 1 to 84 days. The half-life of the enzyme was virtually the same during and after drug administration. These results indicate that phenobarbital increases synthesis of the enzyme, and they illustrate the estimation of enzyme degradation by analysis of the change in enzyme level from one steady state to another.

Estimation of the turnover rate of barbiturate sidechain oxidation enzyme in rat liver.

Premature development of ligandin (GSH transferase B) in mice with an inherited defect in endoplasmic reticulum-Golgi structure and function.

Hypoproteinemia, Chylous Ascites, Steatorrhea, and Protein-Losing Enteropathy due to Chronic Inflammatory Obstruction of Major Intestinal Lymph Vessels

Observations of the effect of diethylnitrosamine on glucuronide formation.

Publisher Summary The entire chemical basis of kernicterus has not yet been fully elucidated, although several major advances have been made in this direction. This chapter consists of a review of these advances and of the methods used in the study of bilirubin conjugation. In this discussion, the term “kernicterus” is used to describe a disease state featuring jaundice of the patient and of the nuclear masses of the brain, accompanied during life by signs of central nervous system dysfunction. The chapter presents clinical states associated with kernicterus. In each of the clinical situations listed, kernicterus has never been seen at birth and, with rare exceptions, is manifested within the first 10 days of life. The clinical manifestations of kernicterus are independent of the clinical state in which kernicterus develops. There are striking similarities between the pathological changes seen in human kernicterus because of various causes and those seen in either homozygous Gunn rats or experimental kernicterus produced by the injection of bilirubin into various species of animals. Various factors have been held responsible for the localized yellow pigmentation in the brain and for the subsequent brain damage. In this chapter, brief comments are made regarding these factors and their apparent importance in the development of kernicterus. The chapter discusses the relationship of the blood-brain barrier to kernicterus and chemical effects of bilirubin on brain metabolism. Mechanisms resulting in unconjugated bilirubinemia in disease states associated with kernicterus are elaborated. Factors affecting distribution of bilirubin in newborn humans and Gunn rats are given. Methods used in the study of Glucuronide formation in vitro are discussed.

Irwin M. Arias

Papers

Estimation of the turnover rate of barbiturate sidechain oxidation enzyme in rat liver.

Premature development of ligandin (GSH transferase B) in mice with an inherited defect in endoplasmic reticulum-Golgi structure and function.

Hypoproteinemia, Chylous Ascites, Steatorrhea, and Protein-Losing Enteropathy due to Chronic Inflammatory Obstruction of Major Intestinal Lymph Vessels

Observations of the effect of diethylnitrosamine on glucuronide formation.

The chemical basis of kernicterus.