Biomedical subjects

A Bast

Publications and source records attributed to A Bast.

At least 181 records · Page 10Linked to original sources

PubMed1990

Isolated mouse atrium as a model to study anthracycline cardiotoxicity: the role of the beta-adrenoceptor system and reactive oxygen species.

Cancer chemotherapy with anthracyclines, of which doxorubicin (DX2) is the main representative, is limited by cardiomyopathy developing in animals and patients after cumulative dosing. The toxicity is probably related to free radical formation by the anthracycline as well as its metabolites with concomitant O2.- and .OH generation resulting in lipid peroxidation and subsequent membrane damage. An in vitro model is required to investigate the individual contribution of each metabolite to cardiotoxicity. For in vivo studies, the species of choice is the mouse because it lacks the DX-induced nephrotic syndrome seen for instance in rats and rabbits. Thus, isolated mouse heart muscle was chosen as an in vitro model. To characterize the model, we used l-isoprenaline/dl-propranolol and metacholine/atropine to measure the beta-adrenergic and the muscarinic responses of (spontaneously beating) right and (paced) left atrium. Dose response curves (n greater than or equal to 4) were highly reproducible: pD2,iso = 8.0 +/- 0.3 (left) and 8.5 +/- 0.4 (right); pD2,met = 6.7 +/- 0.1 (left) and 6.2 +/- 0.3 (right). Propranolol as well as atropine behaved as competitive antagonists, with pA2-values of 8.4 +/- 0.2/8.5 +/- 0.2 (l/r) and 9.1 +/- 0.1/9.1 +/- 0.2 (l/r), respectively. These values corresponded to those obtained with other organ preparations. We tested the effect of DX in two ways: a) by measuring the direct inotropic and chronotropic effect during 60 minutes of incubation with 10-100 microM DX in the organ bath, and b) by determining the remaining beta-adrenergic response to l-isoprenaline after the incubation period. Both variables turned out to be equally affected. For paced left atria an IC50 (causing 50% depression of contractile force) of 35 microM was determined. Right atria stopped beating at concentrations above 50 microM, thus hampering IC50 determination. The results indicate that anthracyclines exert an effect not related to receptor integrity, but directly to the functionality of heart muscle. To check whether radical stress can be involved in the observed negative inotropic effect, incubations with xanthine/xanthine oxidase (to produce reactive oxygen species) were performed. A pronounced negative effect on mouse atrial contraction was indeed observed. However, initially a positive inotropic effect accompanied by an increased resting tension were seen. It can be concluded that mouse atrium can be used as a model to compare anthracyclines and their metabolites with regard to their acute cardiotoxic effects.

Animals↗

PubMed1989

Oxidative stress. Biochemistry and human disease.

The early involvement of free radicals in the evolution of life may explain their ubiquitous presence and vital physiological role. Imbalance between protection against free radicals and their generation, explains the likely association of various diseases with toxic oxygen species. An elaborate defence system against oxygen-free radicals exists. The effects of oxidative stress are manifold. Direct demonstration of oxygen radicals in intact biological systems is difficult. Frequently, effect-related measurements are used in this respect. The clinical conditions adult respiratory distress syndrome and multiple organ failure, reflex sympathetic dystrophy and sugar cataract are discussed and the role of oxygen radicals in the aetiology of these diseases are described.

Free Radicals↗

PubMed1989

Modulation of oxidative stress in the gastrointestinal tract and effect on rat intestinal motility.

The amounts of different factors, which are involved in oxygen free radical production or in protection against oxygen radicals, were determined in different parts of the gastrointestinal tract (GI-tract). Glutathione and superoxide dismutase were present in lower amounts within the small intestine compared with the stomach and the large intestine. In the small intestine glutathione peroxidase and catalase both prevailed in the intestinal muscle compared to the mucosa, whereas in the large intestine both enzymes are equally distributed among the mucosa and muscle. Xanthine oxidase was mainly present in the small intestinal mucosa. Taken together, these results suggest that the large intestine is better provided with protective enzymic and non-enzymic factors against oxidative stress than the small intestine. The protective capacity of different intestinal preparations against lipid peroxidation in liver microsomes was assessed, and particularly the mucosal fractions from the small intestine showed a marked protection against lipid peroxidation, which is not easily explained with the presence of the enzymes measured in this study. Pretreatment of intestinal segments with hydrogen peroxide or cumene hydroperoxide resulted in a damaged contractile response of the longitudinal smooth muscle to methacholine in all parts of the GI-tract, expressed in a lower pD2 value and a decreased maximal response. Pretreatment with these peroxides also decreased contractions after depolarization with K+. The large intestine is more sensitive to hydrogen peroxide and cumene hydroperoxide than the small intestine, which parallels with the sensitivity to lipid peroxidation. The results obtained with hydrogen peroxide also correlate well with the catalase activity in the various segments of the intestine. In conclusion, oxidative stress in the GI-tract alters intestinal motility, especially in the large intestine. Probably this does not occur at the level of muscarinic receptors.

Animals↗

PubMed1989

High affinity, saturable [3H]mepyramine binding sites on rat liver plasma membrane do not represent histamine H1-receptors. A warning.

Rat liver plasma membrane contains a saturable, high affinity binding site for the labelled histamine H1-antagonist [3H]mepyramine. Nonlinear regression analysis of the performed saturation experiments revealed an equilibrium dissociation constant (Kd) of 7.7 +/- 0.4 nM and a maximal binding capacity (Bmax) of 70.4 +/- 9.5 pmol/mg protein. Specific binding could be inhibited completely by several histaminergic ligands. However, the affinities of the tested H1-antagonists other than mepyramine for this binding site were quite low and the known stereospecificity displayed by the histamine H1-receptor for the enantiomers of chlorpheniramine and pheniramine was not found. Moreover, the H2-selective agonist 4-methylhistamine (Ki = 412 microM) was even more potent than its H1-selective 2-methylderivative (Ki = 772 microM). Since several ethylenediamines were also very potent in displacing [3H]mepyramine we suggest the presence of an ethylenediamine recognition site on rat liver plasma membrane which is unrelated to the histamine H1-receptor. It is stressed that a proper pharmacological characterization of a reported binding site is needed, since we show in this study that [3H]mepyramine, which is frequently used in studies concerning the H1-receptor, labels non-H1-receptor binding sites in rat liver plasma membrane.

Aminopyridines↗

PubMed1989

Involvement of protein kinase C in the histamine H1-receptor mediated contraction of guinea-pig lung parenchymal strips.

In this study we investigated the role of protein kinase C (PKC) in the histamine H1-receptor mediated contraction of guinea-pig parenchymal lung strips. Lung strips contract after administration of the PKC activators phorbol-12-myristate-13-acetate (PMA) and dioctanoylglycerol. Prolonged stimulation (45 min.) with a high concentration of PMA abolished subsequent responses to PMA whereas H1-responses were only partially reduced. Administration of a PKC inhibitor (H-7) also led to an inhibition of H1-responses. Experiments with combined incubations with the PKC inhibitor H-7 and the Ca2+-entry blocker verapamil suggest that the PKC contribution to the response is possibly mediated via regulation of Ca2+ influx.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1989

Structural features of some diphenhydramine analogues that determine the interaction with rat liver cytochrome P-450.

The aim of this study was to define the structural characteristics in a series of 21 analogues of the anti-histaminergic drug diphenhydramine which are important for the interaction with cytochrome P-450. The compounds gave substrate (type I) binding spectra with rat hepatic microsomal cytochrome P-450. The main findings were: (1) two phenyl rings are needed for strong binding: saturation or elimination of one ring, or restriction of two phenyls with a two-carbon bridge results in a decrease of binding, (2) substitution on one or both aromatic rings has only a small influence on binding, (3) an amine nitrogen contributes to better binding; decrease or absence of basicity weakens binding, and (4) a chain of 4 to 7 atoms connecting the basic centre with the aromatic part is needed; reduction of the chain length, or restriction of it to a cyclic structure causes decrease or loss of binding ability.

Animals↗

PubMed1989

The effects of cimetidine, ranitidine and famotidine on rat hepatic microsomal cytochrome P-450 activities.

It has been questioned whether the interaction of H2-antagonists with cytochrome P-450 that is observed in vitro is also relevant for the in vivo situation. Until now the possibility that cytochrome P-450 may function with different modes of action has been neglected in this respect. We studied the effect of cimetidine, ranitidine and famotidine on the monoxygenase, the oxidase and the peroxidase action of cytochrome P-450. Biotransformation catalyzed by the monoxygenase and oxidase action of cytochrome P-450 was affected by cimetidine (probably via its ligand interaction with cytochrome P-450), whereas metabolism by the peroxidase mode of action of cytochrome P-450 was hardly influenced. Ranitidine and famotidine (both pharmacodynamically more potent than cimetidine) only slightly affected cytochrome P-450 activities.

Animals↗

PubMed1989

Effect of thiols on lipid peroxidation in rat liver microsomes.

The stimulatory or inhibitory effects of various thiol compounds on in vitro lipid peroxidation by iron-ascorbate in rat liver microsomes were determined. Glutathione had no measurable pro-oxidant capacity, in contrast, it protected against lipid peroxidation. N-Acetyl l-cysteine and S-methyl-glutathione had no effect on in vitro lipid peroxidation. l-Cysteine stimulated lipid peroxidation and also of d-penicillamine and dl-dithiothreitol the pre-oxidant capacity predominated the anti-oxidant capacity. Cysteamine afforded a pronounced protection against in vitro lipid peroxidation. In contrast to the labile character of the glutathione dependent protection, the protection by cysteamine was not affected by heat-pretreatment of the liver microsomes or alkylating protein sulfhydryl groups by N-ethyl maleimide. Again in contrast to glutathione, the protection against in vitro microsomal lipid peroxidation by cysteamine was not reduced after in vivo lipid peroxidation induced by CC14. This suggests that even after the process of lipid peroxidation has been started, administration of cysteamine might still be beneficial.

Acetylcysteine↗

PubMed1989

Contribution of 4-hydroxy-2,3-trans-nonenal to the reduction of beta-adrenoceptor function in the heart by oxidative stress.

Oxidative stress reduces adenylate cyclase activity and also the maximal response to beta-adrenoceptor stimulation in the rat heart, while beta-adrenoceptor density is not affected or increased. Since free sulfhydryl groups are essential to beta-adrenoceptor function and the sulfhydryl reactive substance 4-hydroxy-2,3-trans-nonenal (HNE) is responsible for part of the effects of oxidative stress, the effect of HNE on beta-adrenoceptor function in field stimulated left atria of the rat was determined. To this end field stimulated atria were incubated with 10 microM, 100 microM and 1 mM HNE for 25 min. After removing the excess of HNE, beta-adrenoceptor function was determined by measuring the positive inotropic response to (-)-isoproterenol. It was found that 10 microM HNE had no effect on beta-adrenoceptor function, whereas 100 microM HNE reduced the maximal effect to (-)-isoproterenol without affecting the pD2 (-log EC50). At these concentrations, HNE had no effect on either beta-adrenoceptor density or on c-AMP production. After 1 mM HNE, the atria stopped contracting. Since the effects of the synthetic thiol inactivator N-ethyl maleimide were similar to those of HNE, it was concluded that the reduction of beta-adrenoceptor function by HNE is probably the result of alkylation of free sulfhydryl groups. Our results indicate that the reduction of adenylate cyclase activity by oxidative stress is not mediated by the production of HNE, however oxidative stress and HNE both reduce the maximal response to beta-adrenoceptor stimulation.

Adenylyl Cyclases↗

PubMed1989

Changes in receptor response by the effect of disease on membrane fluidity.

Currently, changes that occur in receptor function under (patho-) physiological conditions are being investigated. The molecular mechanisms causing the observed variations are largely unknown. It is suggested that the pivotal role of the fluidity of the membrane has been neglected in the literature. It is hypothesized that aberrations in receptor function in diseases that are associated with a concomitant mild oxidative stress can be explained by membrane wavering.

Humans↗

PubMed1989

The effects of radical stress and N-ethylmaleimide on rat hepatic alpha 1-adrenergic receptors.

Liver plasma membranes of non-treated rats or rats treated with carbon tetrachloride were prepared. Liver plasma membranes obtained from non-treated rats were preincubated with cumene hydroperoxide, N-ethylmaleimide or hydrogen peroxide in the absence or presence of Fe2+. The effects of in-vivo or in-vitro treatment on hepatic alpha 1-adrenergic receptors were assessed in a [3H]prazosin binding assay. All treatments except preincubation with hydrogen peroxide alone caused a decrease in the number of alpha 1-adrenergic receptors without a change in the affinity of [3H]prazosin. The decrease in receptor number was accompanied by an increase in the level of lipid peroxidation in the plasma membranes. The results indicate that the hepatic alpha 1-adrenergic receptor is vulnerable to free radical stress.

Animals↗

PubMed1989

Interaction of nefopam and orphenadrine with the cytochrome P-450 and the glutathione system in rat liver.

Nefopam, a cyclic analogue of orphenadrine, exhibits a type I (substrate) and a type II (ligand) interaction with ferri-cytochrome P-450 in control and phenobarbitone induced rat hepatic microsomes respectively. In-vitro metabolism of nefopam in phenobarbitone-induced microsomes leads to the production of a reactive metabolite which complexes with cytochrome P-450. In contrast to the known complexation of orphenadrine, complexation by nefopam can be inhibited by glutathione (GSH, 0.1-1.0 mM). However, in-vivo administration of nefopam to rats does not diminish the GSH content of liver cytosol nor increase oxidized glutathione levels nor alter the activities of GSH transferase and GSH peroxidase. In-vivo administration does not lead to cytochrome P-450 induction nor cytochrome P-450 complexation as has been shown for orphenadrine. Finally, nefopam inhibits the NADPH dependent endogenous H2O2 production in both control and phenobarbitone-induced microsomes.

Aminopyrine N-Demethylase↗

PubMed1989

In vitro effect of toluene diisocyanate on beta adrenergic and muscarinic receptor function in lung tissue of the rat.

To investigate the role of pharmacological mechanisms in toluene diisocyanate (TDI) induced occupational asthma, the effects of TDI on rat trachea ring and lung parenchymal strip were studied in vitro. The most prominent effect observed was a stimulation of metacholine (1 microM) induced contraction of the tracheal ring by 1 microM TDI (added in dimethy sulphoxide). The results were less pronounced when TDI was added from a stock solution prepared in water, which is possibly due to (co)polymerisation. It is concluded that the pharmacological effect of TDI may result from an autonomic imbalance between cholinergic and beta-adrenergic neural control.

Animals↗

PubMed1989

Inhibition of superoxide anion radical production by ebselen (PZ51) and its sulfur analogue (PZ25) in guinea pig alveolar macrophages.

The production of superoxide anion radicals by guinea pig alveolar macrophages is stimulated by the chemotactic peptide N-formylmethionyl-leucylphenylalanine and the protein kinase C activator phorbol-12-myristate-13-acetate. Both stimulations are completely and equipotently (IC50 = 20 microM) inhibited by the seleno-organic compound ebselen. As the sulfur containing analogue, which is devoid of glutathione peroxidase-like activity, shows the same inhibitory activity towards superoxide anion radical production the observed effect of ebselen can not be explained by the described glutathione peroxidase-like activity. The observed inhibition is probably caused by an inhibition of protein kinase C or inhibition at a level distal to protein kinase C activation.

Animals↗

PubMed1989

[Oxygen radicals: rescue or threat?].

In this review the chemistry and formation of oxygen radicals is surveyed. Various physiological protective mechanisms against oxygen radicals as well as the consequence of too much or too little oxygen radicals in diseases is discussed. In this respect attention is given to hypoxia/ischemia, bronchopulmonary dysplasia, retrolental fibroplasia, thalassaemia, Down's syndrome and chronic granulomatous disease. Finally some new developments in pharmacotherapeutic possibilities which might play a role in prevention or amelioration of free radical pathologies are mentioned.

Antioxidants↗

PubMed1988

Interplay between lipoic acid and glutathione in the protection against microsomal lipid peroxidation.

Reduced glutathione (GSH) delays microsomal lipid peroxidation via the reduction of vitamin E radicals, which is catalyzed by a free radical reductase (Haenen, G.R.M.M. et al. (1987) Arch. Biochem. Biophys. 259, 449-456). Lipoic acid exerts its therapeutic effect in pathologies in which free radicals are involved. We investigated the interplay between lipoic acid and glutathione in microsomal Fe2+ (10 microM)/ascorbate (0.2 mM)-induced lipid peroxidation. Neither reduced nor oxidized lipoic acid (0.5 mM) displayed protection against microsomal lipid peroxidation, measured as thiobarbituric acid-reactive material. Reduced lipoic acid even had a pro-oxidant activity, which is probably due to reduction of Fe3+. Notably, protection against lipid peroxidation was afforded by the combination of oxidized glutathione (GSSG) and reduced lipoic acid. It is shown that this effect can be ascribed completely to reduction of GSSG to GSH by reduced lipoic acid. This may provide a rationale for the therapeutic effectiveness of lipoic acid.

Animals↗

PubMed1988

Vitamin E and selenium regulate balance between beta-adrenergic and muscarinic responses in rat lungs.

The effects of hydrogen peroxide on the beta-adrenergic and muscarinic responses of the rat trachea muscle were studied in vitro, after feeding rats, for 6 weeks, either a diet deficient in vitamin E and selenium or a control diet. In the control situation after incubation with 1 mM hydrogen peroxide for 30 min, a reduction of the maximal response to methacholine of 39% occurred whereas no pD2 shift could be demonstrated. Moreover, no response to isoprenaline after precontraction with 3 x 10(-7) M methacholine was left. In the deficient situation, we found a reduction to 64% of the response to methacholine after incubation with 1 mM hydrogen peroxide. Again isoprenaline became inactive, i.e. no relaxation with isoprenaline was observed after precontraction with 3 x 10(-7) M methacholine. We therefore conclude that vitamin E and selenium protect against oxidative stress in lung tissue and thus regulate the (patho-) physiological balance between adrenergic and muscarinic responses.

Animals↗

PubMed1988

The effect of chronic adriamycin treatment on heart kidney and liver tissue of male and female rat.

The influence of chronic adriamycin treatment on cellular defence mechanisms against free radicals has been determined in rats. To that end, the changes in vitamin E content, activity of superoxide dismutase, catalase and factors of the glutathione system were measured in heart, kidneys and liver after 24 and 52 days of treatment. Moreover, damage was assessed by measuring the activity of NADPH- and NADH-cytochrome c reductase. The results concerning the components of the oxidative defence systems in male rats showed reductions in the activity of superoxide dismutase and catalase in renal tissue and in factors of the glutathione system in liver tissue. In cardiac tissue an increased activity of catalase and elevated content of total glutathione were found. Vitamin E content was increased in liver and to a lesser extent, in kidneys. The activity of Se-dependent glutathione peroxidase sharply decreased only in liver. Major differences between male and female rats were not observed in renal and cardiac tissue, as far as protective factors were concerned. However, a decrease in catalase activity was detectable earlier in male kidneys. The protective factors in liver of female rats were far less susceptible to in vivo treatment with adriamycin, as compared to liver of male rats. Decreased activity of the cytochrome reductases was found in liver of male rats. In male renal tissue only cytochrome c reductase activity was significantly reduced. Male cardiac tissue showed no signs of biochemical damage, although from histological examination in a parallel study [J Natl Cancer Inst 76: 299-307 (1986)] lesions were evident. In female rats no damage was found in liver, kidneys and heart.

Animals↗