Biomedical subjects

A L Tappel

Publications and source records attributed to A L Tappel.

At least 19 recordsLinked to original sources

PubMed1992

Glutathione and antioxidants protect microsomes against lipid peroxidation and enzyme inactivation.

The study investigated the relationship between lipid peroxidation and enzyme inactivation in rat hepatic microsomes and whether prior inactivation of aldehyde dehydrogenase (ALDH) exacerbated inactivation of other enzymes. In microsomes incubated with 2.5 microM iron as ferric sulfate and 50 microM ascorbate, ALDH, glucose-6-phosphatase (G6Pase) and cytochrome P450 (Cyt-P450) levels decreased rapidly and concurrently with increased levels of thiobarbituric acid-reactive substances. Microsomal glutathione S-transferase and nicotinamide adenine dinucleotide phosphate-cytochrome c reductase were little affected during 1 hr of incubation. Addition of reduced glutathione partially protected and N,N'-diphenyl-p-phenylenediamine and butylated hydroxytoluene completely protected microsomes against inactivation of ALDH, G6Pase and Cyt-P450, as well as lipid peroxidation induced by iron and ascorbate. ALDH was more susceptible than G6Pase to inactivation by iron and ascorbate, and was thus an excellent marker for oxidative stress. Inhibition of ALDH by cyanamide injection of rats exacerbated the inactivation of G6Pase in microsomes incubated with 0.1 mM, but not 25 microM 4-hydroxynonenal (4-HN). 4-HN did not stimulate lipid peroxidation. Thus, 4-HN may play a minor role in microsomal enzyme inactivation. In contrast, lipid peroxyl radicals play an important role in microsomal enzyme inactivation, as evidenced by the prevention of both lipid peroxidation and enzyme inactivation by chain-breaking antioxidants.

Aldehyde Dehydrogenase↗

PubMed1992

Potentiation of oxidative damage to proteins by ultraviolet-A and protection by antioxidants.

We have studied the damage of alcohol dehydrogenase (ADH) and glyceraldehyde 3-phosphate dehydrogenase (GAPD) induced by Fe++/EDTA + H2O2 in combination with UV-A (main output at 365 nm). Enzyme inactivation, formation of hydroxyl radicals (measured in the absence of enzymes), increase in protein carbonyls, oxidation of sulfhydryl (SH) groups, loss of native protein fluorescence, and enhanced protease degradation were used to determine protein damage. Hydroxyl radical production was greatly enhanced by the combination of UV-A with Fe++/EDTA + H2O2. The combined treatment increased protein carbonyls but decreased native protein fluorescence and SH groups. The combined treatment caused turbidity in GAPD but not in ADH, whereas trypsin susceptibility was increased more in ADH than in GAPD. These measurements of protein oxidation correlated well with enzyme activities. Glyceraldehyde 3-phosphate dehydrogenase and dithiothreitol were most protective against such damage, while hydroxyl radical and singlet oxygen scavengers were partially effective. Superoxide dismutase had no effect. Thus, UV-A potentiation of protein damage induced by FE++/EDTA + H2O2 appeared to involve hydroxyl radicals and perhaps singlet oxygen but not superoxide radicals. The damage to proteins induced by combination of UV-A with physiological oxidants, iron ions and H2O2 may be relevant to UV-A-induced skin and tissue damage.

Alcohol Dehydrogenase↗

PubMed1991

Headspace gas chromatography of volatile lipid peroxidation products from human red blood cell membranes.

An improved headspace capillary gas chromatographic (GC) method was developed to measure the oxidative susceptibility of human red blood cell (RBC) membranes. This method analyzed volatile peroxidation products of both n-6 (hexanal and pentane) and n-3 (propanal) polyunsaturated fatty acids. Oxidative susceptibility tests were standardized by incubating in a sealed 10-mL headspace bottle 0.25 or 1 mL of human RBC membrane in 40 mM phosphate buffer for 1 hr at 37 degrees C with a mixture of Fe++, ascorbic acid and H2O2. Sodium dodecyl sulfate increased significantly the amount of hexanal measured by headspace GC. By this standard headspace method, in one series of red blood cell membranes (RBCM) samples a four-fold variation in oxidative susceptibility was observed in RBCM from blood freshly drawn from six healthy subjects. In another series of RBCM samples a sixteen-fold variation in oxidative susceptibility was noted in frozen RBCM from blood freshly drawn from five healthy subjects. Correlation between hexanal formation and polyunsaturated fatty acids (PUFA) depletion provided good evidence that under these standard conditions hexanal is exclusively derived from the oxidation of arachidonic acid. Hydroperoxides of arachidonic acid are more readily formed and decomposed than those of linoleic acid in the presence of Fe++, ascorbic acid and H2O2 to produce hexanal as the main product that can be readily analyzed by headspace GC. This method may provide a useful tool to study susceptibility toward lipid peroxidative damage in human RBC membranes.

Aldehydes↗

PubMed1991

Protein damage and lipid peroxidation: effects of diethyl maleate, bromotrichloromethane and vitamin E on ammonia, urea and enzymes involved in ammonia metabolism.

Changes in ammonia and urea were investigated as potential marker products of free radical damage to protein and subsequent metabolism of those damaged proteins in vivo. Both serum and liver lipid peroxidation products as measured by thiobarbituric-acid-reactive substances (TBARS) were increased by feeding rats a vitamin-E-deficient diet. The acute injection of diethyl maleate and bromotrichloromethane (DEM/BrCCl3) increased TBARS in liver of rats fed a vitamin-E-deficient diet. The concentrations of ammonia and urea in the serum and liver did not correlate with lipid peroxidation. The activities of liver glutaminase and arginase were decreased by DEM/BrCCl3 treatment in rats fed vitamin-E-deficient diet. Glutamate-ammonia ligase activity was decreased by vitamin-E-deficient diet but not by DEM/BrCCl3 treatment. Ornithine carbamoyltransferase, arginosuccinate synthase, argininosuccinate lyase and glutamate dehydrogenase (NAD(P)+) were not affected by dietary vitamin E or by DEM/BrCCl3. The data suggest that the concentrations of ammonia and urea, major by-products of nitrogen metabolism, are unchanged by the oxidant damage and lipid peroxidation, and that their control in vivo is a dynamic equilibrium of various metabolic pathways.

Ammonia↗

PubMed1991

Vitamin E, diethylmaleate and bromotrichloromethane interactions in oxidative damage in vivo.

In vivo interactions of vitamin E with diethylmaleate (DEM) and bromotrichloromethane (CBrCl3) were examined in rats fed a diet either without vitamin E or supplemented with 30 IU dl-alpha-tocopheryl acetate/kg. Groups of rats within each dietary group were given two injections 30 min apart. One group received two injections of the mineral oil carrier. The other groups were injected with either DEM and mineral oil, mineral oil and CBrCl3, or DEM and CBrCl3. The rats were killed 10 min after the second injection. Measurements were made of hepatic GSH, thiobarbituric acid-reactive substances (TBARS) as a lipid peroxidation index, and 11 enzymes as potential markers of oxidant damage. Special focus was placed on reactive cysteine-containing aldehyde dehydrogenase (ALDH). Although dietary vitamin E protected ALDH, the enzyme was highly susceptible to oxidant damage. ALDH activity was correlated with GSH (r = 0.83, p less than 0.001) and there was an inverse relationship between the logarithmic values of ALDH activity and TBARS (r = 0.78, p less than 0.001). Similar results were observed for a number of other enzymes when GSH depletion preceded oxidant treatment. Two-way analysis of variance revealed significant effects of vitamin E and of injection treatments on hepatic GSH. There was a significant interaction between vitamin E and the injection treatments on the activities of five enzymes. The results suggested that vitamin E and GSH functioned together to protect sensitive enzymes against oxidant stress. The sensitive enzymes may be useful markers of hepatic damage in vivo.

Aldehyde Dehydrogenase↗

PubMed1991

Comparative antioxidant effectiveness of dietary beta-carotene, vitamin E, selenium and coenzyme Q10 in rat erythrocytes and plasma.

Five groups of five weanling rats were each fed a Torula yeast-based diet either unsupplemented or supplemented with 30 mg beta-carotene/kg, 30 IU vitamin E/kg, 1 mg selenium/kg or 30 mg coenzyme Q10/kg. Elevated levels of plasma aspartate aminotransferase and alanine aminotransferase are sensitive indicators of liver damage. The former enzyme was lower (P less than 0.01) in the vitamin E-, selenium- and beta-carotene-supplemented groups than in the unsupplemented control group, and the latter enzyme was lower in the vitamin E- and selenium-supplemented groups, suggesting a relatively equal effectiveness of these three antioxidants against liver damage. Erythrocytes were tested for protection against uninduced oxidative damage or that induced by 1 mmol/L bromotrichloromethane (BrCl3C) by measuring thiobarbituric acid-reactive substances (TBARS), hemoglobin, hemolysis, protein precipitation, alanine release and several enzyme activities. In untreated erythrocytes, selenium, beta-carotene and coenzyme Q10 exhibited protection by lowering (P less than 0.05) TBARS and alanine release, but only vitamin E protected against hemolysis. In BrCl3C-treated erythrocytes, vitamin E, selenium and beta-carotene protected by decreasing (P less than 0.05) protein precipitation, whereas selenium and beta-carotene decreased alanine release. The results of this study suggested that, in a manner analogous to vitamin E and selenium, beta-carotene and coenzyme Q10 function as antioxygenic nutrients.

Alanine Transaminase↗

PubMed1990

Oxidant-induced haemoprotein degradation in rat tissue slices: effect of bromotrichloromethane, antioxidants and chelators.

Haemoprotein degradation and lipid peroxidation were evaluated in rat liver, kidney and heart slices incubated for 2 h in the presence and absence of bromotrichloromethane, antioxidants and chelators to obtain information about the relationship between oxidants and damage to haemoproteins. Haemoproteins were modified by bromotrichloromethane, and this modification, measured as loss of ferrohaemoproteins, generally was concurrent with lipid peroxidation measured as thiobarbituric acid-reactive substances. These two processes occurred simultaneously as a function of incubation time and oxidant concentration. Inhibition of the two processes by nordihydroguaiaretic acid, butylated hydroxyanisole and Trolox C, and lack of inhibition by mannitol, catalase and superoxide dismutase also were coincident. However, Methylene blue, EDTA, sodium fluoride, 2,4-dinitrophenol, N-ethylmaleimide and o-phenanthroline affected the two processes differently. The results suggested that haemoproteins may compete with other molecules for oxidant radicals, thus serving as protectors of cells against oxidant radicals. Products of haemoprotein degradation such as protein polymers, free amino acids and bilirubin may be indicators of in vivo oxidative stress.

Animals↗

PubMed1990

Effect of dietary menhaden oil and vitamin E on in vivo lipid peroxidation induced by iron.

Weanling rats were fed diets containing 10% menhaden oil (MO) or 10% corn oil-lard (1:1, COL) with low (less than or equal to 5 IU/kg) or supplementary (35 IU/kg) vitamin E for six weeks. The rats were killed 30 min after injection with 24 mg iron/kg as ferrous chloride because thiobarbituric acid-reactive substances (TBARS) in liver homogenates were highest at 30 min after injection of iron into rats fed a standard diet. Tissue homogenates were used either without incubation (zero-time) or after incubation at 37 degrees C for 1 hr. In addition to TBARS and conjugated dienes, headspace hexanal and total volatiles (TOV) determined by capillary gas chromatography were useful indices of lipid peroxidation since they were decreased by vitamin E supplementation and were increased with increasing iron dose. Regardless of the dietary lipid used, vitamin E supplementation decreased headspace hexanal, TOV, TBARS and conjugated dienes in both zero-time and incubated homogenates of liver and kidney. Dietary MO increased TBARS in both zero-time and incubated homogenates of tissue from rats injected with iron. In contrast, dietary MO decreased hexanal and TOV in incubated tissue homogenates. The study demonstrated the usefulness and limitations of using hexanal and TOV as indices of lipid peroxidation.

Animals↗

PubMed1990

Lipid peroxidation in rat tissue slices: effect of dietary vitamin E, corn oil-lard and menhaden oil.

Rats were fed for 5 weeks either 10% (w/w) menhaden oil (MO) or a 10% corn oil-lard (COL) mixture (1:1) in diets with less than or equal to 5 IU or less than or equal to 2 IU/kg vitamin E, respectively, or the same diets supplemented with d-alpha-tocopheryl succinate to a total of 35 and 180 IU vitamin E/kg, respectively. Slices of liver and heart from these rats were used to study lipid peroxidation in vitro. Thiobarbituric acid-reactive substances (TBARS) were measured in the medium after incubation of the slices at 37 degrees C for 1 hr in the absence (uninduced) and presence of 0.5 mM tert-butyl hydroperoxide (induced). The release of TBARS from slices of heart and liver from rats fed either lipid decreased with increasing levels of dietary vitamin E. At the same level of dietary vitamin E, TBARS release was greater for slices of liver and heart from the MO-fed rats than from the COL-fed rats. Application of the TBARS data to a model simulating the experimental conditions showed a good correlation (r = 0.95, p less than 0.001) between experimental and simulated values. Of the 16:0-22:6 fatty acids measured in liver from MO-fed rats, 15.4% was n-6 fatty acids and 29.9% was n-3 fatty acids; in liver from COL-fed rats, the respective values were 37.4% and 3.7%. Liver and kidney vitamin E levels were unaffected by the dietary lipid.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Lability of red blood cell membranes to lipid peroxidation: application to humans fed polyunsaturated lipids.

Red blood cell membranes (RBCM) were used to estimate human red blood cell lability to lipid peroxidation in vitro. RBCM were prepared from blood collected from humans fed diets with either 3 or 15% polyunsaturated fatty acids for 80 days. RBCM were isolated by centrifugation, and oxidative stress was induced by in vitro incubation with 0.1 or 0.5 mM tert-butyl hydroperoxide (t-BOOH) in the presence of 0.5 mg added hemoglobin. Lipid Peroxidation was evaluated by measurement of thiobarbituric acid-reactive substances (TBARS). Lipid peroxidation correlated with the protein content of RBCM in both noninduced and t-BOOH-induced lipid peroxidation systems. TBARS production was dependent on the amount of t-BOOH added to the RBCM. The production of TBARS by RBCM incubated with 0.5 mM t-BOOH was correlated with arachidonic acid content in the red blood cells (RBC) from which RBCM were prepared. The methodology developed was useful for comparative estimations of the lability of RBCM to lipid peroxidation.

Adult↗

PubMed1990

Oxidant-increased proteolysis in rat liver slices: effect of bromotrichloromethane, antioxidants and effectors of proteolysis.

Proteolysis and lipid peroxidation were evaluated in rat liver slices incubated in the presence of the oxidant bromotrichloromethane and effectors of proteolysis. Proteolysis was evaluated by S-amino acids and lipid peroxidation by thiobarbituric acid-reactive substances (TBARS) released into the incubation medium. The increased release of S-amino acids by BrCl3C depended on incubation time and oxidant concentration. S-Amino acid release increased 30% over control value and TBARS increased from 22 to 124 nmol/g liver by incubation for 120 min with 1 mM BrCl3C. Release of S-amino acids and TBARS was decreased when liver slices were treated with nor-dihydroguaiaretic acid (NDG), butylated hydroxyanisole (BHA), Trolox C, or N,N'-diphenyl-1,4-phenylenediamine (DPPD) immediately prior to addition of oxidant, suggesting participation of lipid-soluble free radicals. Oxidant-induced release of S-amino acids but not of TBARS was decreased by mannitol, suggesting participation of hydroxyl radical or a species with similar reactivity; and by superoxide dismutase and catalase, suggesting participation of superoxide and hydrogen peroxide, respectively. The decrease of S-amino acid release by sodium fluoride, sodium arsenate, 2,4-dinitrophenol, chloroquine, leupeptin, phenylmethylsulfonyl fluoride, EDTA and o-phenanthroline was variable, suggesting the presence in liver of several proteases to remove oxidatively-modified proteins.

Animals↗

PubMed1990

Multiple selenocysteine content of selenoprotein P in rats.

Partially purified selenoprotein P from rat plasma was digested with either trypsin, endoprotease Lys-C, or endoprotease Arg-C and analyzed by high pressure liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Several 75Se-labeled peptides were detected. The moles of selenium in selenoprotein P were estimated based on the 75Se content of the 75Se-labeled peptide fragments. Using this method, selenoprotein P was shown to contain approximately 9 moles of selenium. This is the first report of a selenoprotein containing more than one selenium per polypeptide. These findings support the proposed function of this protein in selenium transport.

Animals↗

PubMed1990

Can serum bilirubin be an index of in vivo oxidative stress?

Bilirubin has been suggested as a physiological antioxidant, and recent studies suggest that its synthesis is induced in response to oxidative stress. Numerous reports in the literature show increases in serum bilirubin when using halogenated hydrocarbons as oxidative stress inducers. Analogously, these increases should also be expected for other inducers. On the other hand, bilirubin is destroyed by the same molecules that induce its production. The measurement of bilirubin may be a useful index of in vivo oxidative stress, although no big differences in bilirubin levels should be expected.

Animals↗

PubMed1990

Damage to red blood cells by halocompounds.

Twenty-five halocompounds were screened as inducers of hemoglobin degradation and lipid peroxidation in rat red blood cells (RBC). RBC activated halocompounds, and oxyhemoglobin remaining depended on the halocompounds employed. Thiobarbituric-acid-reactive substances (TBARS), an index of lipid peroxidation, also depended on the halocompound. TBARS were inversely correlated and oxyhemoglobin percentage was directly correlated with the logarithm of oral LD50 of the halocompounds (r = 0.79, P less than 0.001, and r = 0.87, P less than 0.001, respectively). For 15 halocompounds, the oral LD50 calculated as log LD50 = 0.015 (% hemoglobin) -0.05 (TBARS) were correlated (r = 0.88, P less than 0.01) with the reported oral LD50.

Animals↗

PubMed1990

Dietary supplements of vitamin E, beta-carotene, coenzyme Q10 and selenium protect tissues against lipid peroxidation in rat tissue slices.

A tissue slice model was employed to assess the effects of dietary antioxidant supplements on lipid peroxidation. In one experiment, rats were fed diets containing, either alone or in combination, vitamin E, selenium, beta-carotene or coenzyme Q10 for 42 d, and the extent of spontaneous and induced lipid peroxidation was determined by release of thiobarbituric acid-reactive substances (TBARS) into the medium. Vitamin E exhibited the greatest protection against lipid peroxidation in liver, heart and spleen; in kidney, selenium was most protective. Coenzyme Q10 was active against lipid peroxidation induced by tertbutyl hydroperoxide (t-BHP). In a second experiment, rats were fed diets containing varying amounts of vitamin E, selenium, beta-carotene and coenzyme Q10 for 30 d. Spontaneous lipid peroxidation in liver, kidney and heart decreased with increasing levels of dietary antioxidants. With increasing amounts of antioxidants, there was a diminution in TBARS released by liver and kidney slices incubated with t-BHP; in heart, only the highest levels of antioxidants significantly decreased production of TBARS. Inverse correlations between dietary vitamin E and TBARS, tissue vitamin E and TBARS, and tissue selenium-glutathione peroxidase and TBARS were highly significant. The procedure used here can evaluate dietary supplements that may find practical applications in decreasing the oxidant radical portion of disease processes.

Animals↗

PubMed1989

Rat plasma selenoprotein P properties and purification.

A selenoprotein in rat plasma, selenoprotein P, was fractionated and characterized. Plasma collected from rats 3 h post injection of 75SeO3(2-) contained one 75Se-labeled protein, selenoprotein P. Selenoprotein P was fractionated using salt precipitation, Affi-Gel Blue, and DEAE chromatography. The 75Se-containing subunit of selenoprotein P was purified to 90% homogeneity using SDS-polyacrylamide gel electrophoresis followed by electroelution. This isolation resulted in an 850-fold purification of the 75Se-containing subunit of selenoprotein P with a 15% yield of 75Se radioactivity. The molecular weight of selenoprotein P in plasma was 98,000. The 75Se-containing subunit of selenoprotein P had a molecular mass of 57 kDa as determined by SDS-polyacrylamide gel electrophoresis. Isoelectric focusing under nondenaturing conditions resulted in a band of 75Se radioactivity at pH 5.4. A comparison of Coomassie Blue- and silver-staining properties of selenoprotein P in SDS-polyacrylamide gels was made. Reverse-phase HPLC and Sephadex G-50 chromatography of tryptic peptides of the 57 kDa subunit of selenoprotein P yielded several peaks of 75Se radioactivity. These results indicate that 75Se is present in several locations within the 57 kDa subunit of selenoprotein P.

Animals↗

PubMed1989

Selenoprotein P receptor from rat.

Radioreceptor assay technology was used to show the presence in the rat of a receptor that binds selenoprotein P, a selenocysteine-containing rat plasma protein. 75Se-labeled selenoprotein P bound to testis, kidney, and liver membranes. The binding was specific in that increasing amounts of partially-fractionated rat plasma specifically displaced the binding of 75Se-labeled selenoprotein P to testis membrane in a competitive manner. 75Se-labeled selenoprotein P binding was saturable in the presence of increasing amounts of testis membranes. The binding of 75Se-labeled selenoprotein P was optimal at about pH 4.2. Several proteins and blood fractions had little or no significant effect on binding of 75Se-labeled selenoprotein P to testis membranes. All plasma sources tested specifically displaced 75Se-labeled selenoprotein P from testis membrane, indicating that selenoprotein P-related proteins may be widespread in nature. The study indicated that selenoprotein P has a receptor and is involved in selenium transport.

Animals↗

PubMed1989

Rapid headspace gas chromatography of hexanal as a measure of lipid peroxidation in biological samples.

A rapid, sensitive and convenient capillary gas chromatographic-headspace method was developed to determine hexanal as an important volatile decomposition product of hydroperoxides formed from n-6 polyunsaturated fatty acids in rat liver samples. Total volatiles were also determined as a measure of overall lipid peroxidation. Samples of headspace taken from sealed serum bottles incubated at 37 degrees C were injected into a gas chromatograph. It was possible to make 15 determinations per hour. This method is convenient because no special sample manipulations are necessary. The addition of 0.5 mM ascorbic acid prior to gas chromatographic analysis significantly increased hexanal production. The applicability of the method was demonstrated in studies of the effect of iron in the presence or absence of hydroperoxides of methyl linoleate and methyl linolenate and tert-butyl hydroperoxide on rat liver homogenates, slices and microsomes. A rapid silica cartridge chromatographic procedure was used to purify hydroperoxides from autoxidized methyl linoleate and methyl linolenate, and hydroperoxy epidioxides (cyclic peroxides) from autoxidized methyl linolenate in 20-40 mg quantities. The hydroperoxides and hydroperoxy epidioxides of methyl linolenate were effective inducers of n-6 polyunsaturated fatty acid peroxidation in liver homogenates. Hexanal and thiobarbituric acid-reacting substances were significantly correlated in liver homogenates and microsomes but not in slices. This specific method for hexanal, a known product of peroxidation of n-6 polyunsaturated fatty acids, can be used as a good measure of lipid peroxidation.

Aldehydes↗