Biomedical subjects

A L Tappel

Publications and source records attributed to A L Tappel.

At least 55 records · Page 3Linked to original sources

PubMed1989

Lipid peroxidation products in biological tissues.

Over the past twenty-years of lipid peroxidation research in this laboratory, considerable effort has gone into development of new methods, with emphasis on measurement of lipid-soluble fluorophores and the volatile hydrocarbons ethane and pentane. Application of these and other methods has been made to biological materials and living animals. Although the various methodologies used in lipid peroxidation research do not necessarily measure the same class of products, and although agreement of results is not always 100%, there is substantial documentation of good correlations between measurements; for example, of trace volatile hydrocarbons with thiobarbituric acid-reacting substances, of pentane production with dietary and/or tissue vitamin E content, and of pentane production with lipid-soluble fluorophores accumulated in spleen as a function of oxidant stress. Individual methodologies do have their inherent limitations. However, measurements of multiple products and their correlations have added significantly to the base of information on biological damage and protection by dietary antioxidants against nutritional and toxicological insults to tissues, cells, and macromolecules as a result of peroxidative and oxidative reactions.

Animals↗

PubMed1989

Application of simulation modeling to lipid peroxidation processes.

A quantitative simulation model was developed that utilized present knowledge of lipid peroxidation in biological systems. The simulation model incorporated the following features: peroxidizability of polyunsaturated lipids, activation of inducers and their initiation of lipid peroxidation, concurrent autoxidation, inhibition of lipid peroxidation by vitamin E, reduction of some of the hydroperoxides by glutathione peroxidase, and formation of thiobarbituric acid-reactive substances. Simulation calculations were done using a computer spreadsheet program. When the simulation program was applied to tissue slice and microsomal peroxidizing systems, the results of the stimulation were in agreement with the experimental data.

Benzene Derivatives↗

PubMed1989

Effect of dietary lipids and vitamin E on in vitro lipid peroxidation in rat liver and kidney homogenates.

Rats were fed for 5 wk 10% (wt/wt) menhaden oil (MO) or a 10% corn oil-lard (COL) mixture (1:1) in diets with a low vitamin E content (less than or equal to 5 mg/kg) or supplemented with d-alpha-tocopheryl succinate to a total of 30 or 150 mg per kg. Thiobarbituric acid-reactive substances (TBARS), conjugated dienes (CD), hexanal and total volatiles (TOV) were measured in tissue homogenates incubated at 37 degrees C for 1 h in the absence (uninduced) and presence of 15 microM ferrous sulfate (induced). The fatty acid composition of liver and kidney reflected that of dietary lipids. For uninduced peroxidation, there was in general a significant inverse correlation of TBARS, CD and TOV with the log of dietary vitamin E content for liver and kidney from rats fed either lipid. For induced peroxidation, the inverse correlation was significant for liver, but not for kidney, from rats fed either lipid. The correlation was generally higher for liver and kidney from rats fed COL than for tissues from rats fed MO. Vitamin E was thus a more effective antioxidant for liver than for kidney regardless of the dietary lipid, and for liver and kidney from rats fed COL than from rats fed MO. Dietary MO enhanced tissue susceptibility to both peroxidation systems. A simulation model developed to mimic the experiments showed good correlations between experimental data and simulated values.

Analysis of Variance↗

PubMed1988

Damage to DNA concurrent with lipid peroxidation in rat liver slices.

Lipid peroxidation and DNA damage were evaluated in liver slices incubated for 2 h at 37 degrees C with 1 mM-t-butyl hydroperoxide (t-BOOH), 1 mM-BrCCl3 or 50 microM-ferrous iron. t-BOOH induced the greatest amount of damage to DNA and increased the production of thiobarbituric acid-reactive substances (TBARS). Both phenomena depended on the incubation time. Ferrous iron induced both DNA damage and TBARS production, and BrCCl3 did not induce significant DNA damage and was the weakest TBARS inducer. Butylated hydroxytoluene at 1 mM inhibited both DNA damage and TBARS production. DNA damage and lipid peroxidation in liver slices were correlated, indicating that these events were concurrent.

Animals↗

PubMed1988

In vivo effects of aurothioglucose and sodium thioglucose on rat tissue sulfhydryl levels and plasma sulfhydryl reactivity.

The active component of aurothioglucose (ATG) in effecting changes in plasma sulfhydryl (SH) levels and plasma SH reactivity with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) was determined. These two measurements are applied clinically to rheumatoid arthritis patients undergoing chrysotherapy. Normal rats were injected intramuscularly daily for seven days with 30 mumol of either ATG or sodium thioglucose (STG)/kg body wt or with an equivalent volume of the carrier, 0.05% benzyl alcohol. ATG but not STG significantly increased total SH levels in plasma, liver, and kidney. The seven-day treatment with ATG significantly increased glutathione levels in kidney but not in liver or plasma. Thus, gold(I) rather than thioglucose was the active moiety that affected SH levels in ATG-injected rats. In vivo, gold(I) was also the active moiety that stimulated plasma SH reactions with DTNB at pH 7.4, since injection of ATG but not STG stimulated the SH reactivity in fresh plasma. In vitro, ATG increased the rate of plasma reaction with DTNB at pH 7.4, thus, gold(I) ions acted as a catalyst in the SH-disulfide exchange reaction. This study demonstrates that gold(I) but not its thiol ligand strongly interacts with protein SH groups in the rat tissues. Such an interaction may play an important role in the biological actions of gold.

Albumins↗

PubMed1988

Selenium-containing proteins of rat kidney.

Rat kidney selenium (Se)-containing proteins were studied by isotopic labeling with [75Se]selenite or [75Se]selenomethionine via three routes: oral, intraperitoneal injection, and incubation of kidney slices with the isotope. The two major Se-containing proteins in kidney were fractionated and partially characterized. 75Se elution profiles from Sephadex G-150 chromatography were similar for each labeling protocol, except for the profile obtained following incubation of slices with [75Se]selenomethionine. Of the two major 75Se-containing proteins, the one eluting at the void volume during Sephadex G-150 fractionation had a subunit of 23,000 Mr. The 75Se-labeled tryptic peptide from this protein and a 75Se-containing tryptic peptide from glutathione peroxidase had the same elution time from an HPLC column. A 75,000 Mr 75Se-containing protein had a 65,000 Mr subunit, and the 75Se-labeled tryptic peptide from this protein eluted from the HPLC column before that of glutathione peroxidase. Glutathione peroxidase is the most abundant kidney selenoprotein. Injection of animals with 75Se is the method of choice for isotopic labeling of rat kidney Se-containing proteins. Appropriate methods were developed that can be used in future studies of kidney Se-containing proteins.

Animals↗

PubMed1988

Effect of chronic aurothioglucose treatment of rats on kidney catalase and cytochromes.

Catalase activity and cytochrome content were measured in kidneys of Fisher 344 rats injected with aurothioglucose (ATG) either daily for 3 days or 5 days a week for up to 8 wk. Catalase activity was decreased 39%, 59%, and 48% (all p less than 0.001) after 3 days, 2 wk, and 8 wk, respectively. Microsomal cytochrome P-450 levels decreased 71%, 86%, and 80% (all p less than 0.001) after 3 days, 2 wk, and 8 wk, respectively. In contrast, cytochrome b5 was significantly increased at 3 days and 2 wk, but not at 8 wk. Microsomal heme contents decreased 44% (p less than 0.001), 34% (p less than 0.001), and 22% (p greater than 0.05) at 3 days, 2 wk, and 8 wk, respectively. The content of mitochondrial cytochromes aa3, b, c1, and c were not affected after 8 wk of ATG treatment. In vitro inhibition of the heme-containing enzyme delta-aminolevulinic acid dehydratase by ATG was reversible in the presence of physiological concentrations of small thiols. Although the activity of this enzyme in kidneys of ATG-treated rats was not measured, its significant inhibition in vivo by ATG appears unlikely. This study demonstrates that there were differential effects of gold on the various cytochromes and that changes in catalase activity paralleled changes in cytochrome P-450 and heme contents in the kidneys of ATG-treated rats. The findings are relevant to nephrotoxicity during chrysotherapy.

Animals↗

PubMed1988

Interactions of selenium and cadmium with metallothionein-like and other cytosolic proteins of rat kidney and liver.

Following injection of rats with CdCl2 and [75Se]selenite using five different protocols, the metallothionein-like proteins (MTLPs) of kidney and liver cytosols were fractionated by Sephadex G-75 gel filtration and DEAE Sephacel ion-exchange chromatography. Cd and 75Se distribution in gel-filtration elution profiles was influenced mainly by the time that elapsed between administration of these elements and by the sequence of their administration. There was no Cd redistribution to high molecular weight proteins after long-term Cd injection when rats were killed 48 hr after 75Se injection. Cd was redistributed from MTLP to high molecular-weight proteins in the liver when Cd and 75Se were injected within 1-3 hr of each other. Incorporation of 75Se into MTLP of kidney and liver was independent of Cd injection. The strength of 75Se binding of MTLP was comparable to the covalent binding of 75Se to glutathione peroxidase. Cd and 75Se did not share binding sites on MTLP. In ligand-exchange studies, 1000 ppm Cd did not displace 75Se from MTLP, but 2% 2-mercaptoethanol displaced 10% of the presumably nonspecifically bound 75Se from kidney and liver MTLP. This study provides new information regarding the apparent covalent binding of Se to low molecular-weight, Cd-containing proteins in kidney and liver.

Animals↗

PubMed1988

Interactions of gold with cytosolic selenium-containing proteins in rat kidney and liver.

Rats injected with aurothioglucose (ATG) for 5 days were subsequently injected with [75Se]selenious acid and killed after 3 days. Kidney and liver cytosols were chromatographed on Sephadex G-150. 75Se in kidney was associated with high molecular weight (HMW), 85,000 Mr, 26,000 Mr, and 10,000 Mr proteins and with a nonprotein fraction. The elution profile of liver cytosol was similar to that of kidney, but without a 26,000 Mr protein. ATG injection increased the association of 75Se with all fractions of kidney cytosol except the 85,000 Mr fractions, which contained Se-glutathione peroxidase (SeGSHPx) activity; 75Se in liver was increased only in HMW fractions. Unfractionated kidney cytosolic SeGSHPx activity was decreased 14% by ATG injection, but liver enzyme activity was not changed. However, Sephadex G-150 chromatography showed that total and specific activities, respectively, were decreased 28 and 23% in kidney and 25 and 16% in liver. Au coeluted with HMW and 10,000 Mr 73Se-containing kidney proteins; the latter contained 50% of the Au eluted from the column. DEAE Sephacel chromatography of the 10,000 Mr kidney protein showed that both Au and 75Se were tightly associated with metallothionein-like proteins. This study demonstrates the interaction of Au with rat liver and kidney 75Se-containing proteins.

Animals↗

PubMed1988

Lipid peroxidation measured as thiobarbituric acid-reactive substances in tissue slices: characterization and comparison with homogenates and microsomes.

Liver slices were used to measure lipid peroxidation induced by bromotrichloromethane, tert-butyl hydroperoxide (t-BOOH), or ferrous iron. The responses of liver homogenates and microsomes to oxidative conditions were compared with the response of tissue slices. Lipid peroxidation was evaluated by the production of thiobarbituric acid-reactive substances (TBARS). As was observed in homogenates and microsomes, TBARS production by liver slices depended upon the amount of tissue, the incubation time, inducer, the amount of inducer, and the presence of antioxidant. Control liver slices incubated at 37 degrees C for 2 h produced 19 nmol of TBARS per g of liver. When slices were incubated in the presence of 1 mM BrCCl3, 1 mM t-BOOH, or 50 microM ferrous iron, TBARS production increased 4.6-, 8.2-, or 6.7-fold over the control value, respectively. Comparable induction of TBARS by liver homogenates and microsomes was observed when these preparations were incubated with the same inducers. Addition of 5 microM butylated hydroxytoluene (BHT) prevented the induction of TBARS by 50 microM ferrous iron by liver slices. The results indicate the usefulness of tissue slices to measure lipid peroxidation. The usefulness of tissue slices is emphasized when a number of compounds or tissues are studied and tissue integrity is desired as in toxicological, pharmacological, and nutritional studies where reduced numbers of experimental animals is a relevant issue.

Animals↗

PubMed1988

Aurothioglucose effect on sulfhydryls and glutathione-metabolizing enzymes: in vivo inhibition of selenium-dependent glutathione peroxidase.

Fisher 344 rats injected with a total of 20.8 +/- 1.5 mg of gold (Au) as aurothioglucose over an 8-wk period were used to study the effect of long-term Au treatment on selenium-dependent glutathione peroxidase (SeGSHPx), other enzymes related to GSH metabolism, GSH, nonprotein sulfhydryls, and total sulfhydryls (SH) in various tissues. The indirect coupled assay for SeGSHPx revealed decreased activity in platelets of Au-treated rats but not in other tissues. Inhibition of SeGSHPx by Au is reversible upon dilution. A direct assay of GSH consumption by concentrated tissue cytosols that was developed to minimize enzyme dilution provided evidence of in vivo inhibition of SeGSHPx in kidney and liver from Au-injected rats. Kidneys of these rats had decreased (P less than 0.05) activities of GSSG reductase (36%), gamma-glutamylcysteine synthetase (19%), and gamma-glutamyl transpeptidase (26%), and increased (P less than 0.05) activities of glucose 6-phosphate dehydrogenase (90%) and GSH S-transferase (130%). The reactivity of fresh plasma SH groups with 5,5'-dithiobis-(2-nitrobenzoic acid) increased as a function of injection time. Enhanced SH reactivity suggests that Au may react with protein GSH-disulfides to release GSH. New findings were (i) decreased platelet SeGSHPx and kidney GSSG reductase in aurothioglucose-injected rats, (ii) direct in vivo inhibition of kidney and liver SeGSHPx in aurothioglucose-injected rats, and (iii) no significant correlation between the activity of GSH-metabolizing enzymes and levels of tissue GSH.

Animals↗

PubMed1987

Effect of aurothioglucose on glutathione and glutathione-metabolizing and related enzymes in rat liver and kidney.

The antirheumatic drug aurothioglucose is an inhibitor of the selenoenzyme GSH peroxidase. During chrysotherapy, the decreased levels of erythrocyte GSH and serum sulfhydryls of rheumatoid arthritis patients are normalized concomitant with clinical efficacy. This investigation examined the in vivo and in vitro effect of gold(I) as aurothioglucose on enzymes related to the GSH redox cycle or metabolism. The enzymes measured were GSH peroxidase, GSSG reductase, gamma-glutamyl transpeptidase, gamma-glutamylcysteine synthetase, GSH S-transferase, GSH thiotransferase, glucose-6-phosphate dehydrogenase, superoxide dismutase and catalase. Rats were injected with 30 mumol aurothioglucose/kg body wt. daily for 7 days by intramuscular injection. GSH levels in aurothioglucose-treated rats were 68% higher in erythrocytes (P less than 0.005) and 45% higher in kidney (P less than 0.001) than in control rats. Treatment with aurothioglucose did not elevate plasma or liver GSH. The enzyme activities that were changed by aurothioglucose treatment were GSH peroxidase in kidney (41% decreased, P = 0.005) and liver (13% decreased, P less than 0.05), gamma-glutamyl transpeptidase in kidney (15% decreased, P less than 0.05), and catalase in kidney (58% decreased, P less than 0.001). Kidney glucose-6-phosphate dehydrogenase activity was increased 50% (P less than 0.005) and GSH S-transferase was increased 72% (P less than 0.001). In vitro the only liver enzymes inhibited more than 50% by concentrations of less than 50 microM aurothioglucose were GSH peroxidase (50% inhibited by 25 microM aurothioglucose) and GSH thiotransferase (50% inhibited by 5 microM aurothioglucose). Studies of in vitro enzyme inhibition by aurothioglucose could not be used to predict decreased enzyme activities in vivo. Although decreased activities of two major enzymes that utilize GSH, GSH peroxidase and gamma-glutamyl transpeptidase, coincided with elevated GSH in kidneys of aurothioglucose-treated rats, a direct cause and effect relationship remains speculative.

Animals↗

PubMed1987

Selenium as a sulfhydryl redox catalyst and survey of potential selenium-dependent enzymes.

The ability of selenium (Se) to act as a redox catalyst is an important factor in understanding the biological function of selenoproteins in addition to that of GSH peroxidase. Selenocystine at micromolar levels exhibited pseudothiotransferase activity by enhancing the reduction of 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB) by thiols. In contrast, selenite inhibited the reduction of DTNB by thiols. Selenite was more catalytic than selenocystine in the reduction of cytochrome c by GSH, whereas GSH peroxidase was a weak catalyst. Tissues from Se-deficient and Se-supplemented rats were assayed for activities of GSH-thiotransferase, NADPH cytochrome c reductase, formaldehyde dehydrogenase, and a hypothesized GSH cytochrome c reductase. GSH-thiotransferase activity was significantly increased in the liver of Se-deficient rats. No appreciable activity of this enzyme was found in the kidney of rats from either dietary group. No enzymatic activity for cytochrome c reduction by GSH was detected in cytosols, mitochondria, or microsomes from liver and kidney of Se-deficient or Se-supplemented rats. Formaldehyde dehydrogenase was significantly higher in liver cytosols from Se-supplemented rats than from Se-deficient rats. The higher activity was not attributed to Se-containing proteins, but to an unknown small molecular-weight factor. This study did not support the hypothesis that physiological levels of Se may be involved in sulfhydryl-disulfide exchange reactions in vivo, or that selenium may enhance cytochrome c reduction by GSH in vivo.

Animals↗

PubMed1987

Halogenated compounds as inducers of lipid peroxidation in tissue slices.

Twenty-seven halogenated compounds were screened as potential inducers of lipid peroxidation in rat liver, kidney, spleen, and testes slices. In addition to the known lipid peroxidation inducers--carbon tetrachloride and bromotrichloromethane--the novel compounds carbon tetrabromide, p-bromobenzyl bromide, and benzyl bromide increased lipid peroxidation in each of the tissues studied. Lipid peroxidation was measured by release of thiobarbituric acid-reactive substances (TBARS) from the tissue slices. The amount of TBARS released from liver slices incubated with bromotrichloromethane, carbon tetrabromide, dichloromethane, bromobenzene, chloroform, bromoform, benzyl chloride, bromochloromethane, and carbon tetrabromide correlated with the lethality of these compounds as evaluated by their oral LD50 in rats. The lethality of a number of the compounds tested did not correlate with their capacity to induce lipid peroxidation.

Animals↗

PubMed1986

Effects of ligands on gold inhibition of selenium glutathione peroxidase.

Gold inhibits selenium-dependent glutathione peroxidase (GSH Px) in vitro. Chrysotherapy has been used for over five decades without complete understanding of its pharmacodynamics. This study shows that gold is potentially an inhibitor of GSH Px in vivo. Reported are conditions for assay of GSH-Px activity showing that the inhibition by gold species can be reversed. The study demonstrates the high affinity of gold for the selenohydryl-active site of GSH Px relative to the affinities of other physiological ligands; GSH Px was inhibited to a greater extent by a small molecular-weight fraction isolated from kidneys of gold-treated rats than by the fraction isolated from kidneys of rats not treated with gold. The data provide a new perspective on the action of gold-containing drugs in vivo.

Animals↗

PubMed1986

Mercury, silver, and gold inhibition of selenium-accelerated cysteine oxidation.

In vivo, cysteine in proteins or glutathione is the major amino acid involved in sulfhydryl oxidation-reduction reactions. An in vitro model of cysteine oxidation accelerated by selenium compounds was used to study the interaction of selenocystine and sodium selenite with metal ions. The interaction of metal ions with selenium compounds inhibited cysteine oxidation. The ionic forms of three toxic soft-acid metals, mercury, silver, and gold, were the most effective inhibitors. The antiarthritic gold drugs, aurothiomalate and aurothioglucose, were of particular interest as they inhibit the activity of selenium-glutathione peroxidase. The effect of gold ligands on gold(I) inhibition of selenocystine-accelerated cysteine oxidation was tested. Sodium cyanide partially reversed inhibition and potassium iodide had no effect. Inhibition of selenium-accelerated oxidation-reduction reactions by soft-acid metal ions may be of biological relevance during toxicities or during antiarthritic gold therapy.

Cysteine↗

PubMed1986

Are some major in vivo effects of gold related to microenvironments of decreased selenium?

Gold interacts with selenium in vivo, and the normal distribution of selenium among tissues and subcellular compartments changes. Literature evidence shows that many of the effects of gold compounds on the polymorphonuclear neutrophil, macrophage, and lymphocyte cellular components of the immune system are similar to effects observed in these cellular components in selenium-deficient animals. Affected by these two metals are immune functions related to phagocytic cell migration, phagocytosis, microbial killing, lymphocyte mitogenesis/DNA synthesis, arachidonic acid metabolism/prostaglandin synthesis, and immunoglobulin production. The interaction of gold with selenium in vivo may be responsible for some of the multiparameter-based actions of gold compounds used in the treatment of inflammatory diseases such as rheumatoid arthritis. One mechanism by which gold exerts its clinical effects may be related to its interaction with selenium to produce, in specific microenvironments, decreased levels of this essential trace element.

Animals↗

PubMed1986

Halogenated hydrocarbon and hydroperoxide-induced peroxidation in rat tissue slices.

Tissue slices were used to compare relative peroxidation capacity of bromotrichloromethane (BrCCl3) and t-butyl hydroperoxide (BHP) by measurement of both peroxidation products and biochemical indices of damage. In liver and testes slices, BHP increased thiobarbituric acid reactive-substances (TBARS) and total aldehydes, measured as cyclohexanedione-reactive substances (CHDRS), to a greater extent than did an equimolar amount of BrCCl3. GSH was decreased more by BHP than by BrCCl3. Neither compound released lactate dehydrogenase or glutamic-pyruvic transaminase from liver slices. Treatment of rats with cyanamide, an aldehyde dehydrogenase inhibitor, increased the total CHDRS in liver slices and medium after incubation with BHP or BrCCl3. HPLC of the CHDRS showed hexanal and propanal increased to the greatest extent. The hydroperoxide, BHP, which does not require metabolism to an active species, was a better initiator of peroxidation than the halogenated hydrocarbon, BrCCl3, which must be metabolized to a radical species before it can initiate peroxidation.

Animals↗