Effect of N-methyl deuteration on metabolism and pharmacokinetics of enzalutamide.

BACKGROUND: The replacement of hydrogen with deuterium invokes a kinetic isotope effect. Thus, this method is an attractive way to slow down the metabolic rate and modulate pharmacokinetics. PURPOSE: Enzalutamide (ENT) acts as a competitive inhibitor of the androgen receptor and has been approved for the treatment of metastatic castration-resistant prostate cancer by the US Food and Drug Administration in 2012. To attenuate the N-demethylation pathway, hydrogen atoms of the N-CH3 moiety were replaced by the relatively stable isotope deuterium, which showed similar pharmacological activities but exhibited favorable pharmacokinetic properties. METHODS: We estimated in vitro and in vivo pharmacokinetic parameters for ENT and its deuterated analog (d3-ENT). For in vitro studies, intrinsic primary isotope effects (K H/K D) were determined by the ratio of intrinsic clearance (CLint) obtained for ENT and d3-ENT. The CLint values were obtained by the substrate depletion method. For in vivo studies, ENT and d3-ENT were orally given to male Sprague Dawley rats separately and simultaneously to assess the disposition and metabolism of them. We also investigated the main metabolic pathway of ENT by comparing the rate of oxidation and hydrolysis in vitro. RESULTS: The in vitro CLint (maximum velocity/Michaelis constant [V max/K m]) of d3-ENT in rat and human liver microsomes were 49.7% and 72.9% lower than those of the non-deuterated compound, corresponding to the K H/K D value of ~2. The maximum observed plasma concentration, C max, and area under the plasma concentration -time curve from time zero to the last measurable sampling time point (AUC0-t) were 35% and 102% higher than those of ENT when orally administered to rats (10 mg/kg). The exposure of the N-demethyl metabolite M2 was eightfold lower, whereas that of the amide hydrolysis metabolite M1 and other minor metabolites was unchanged. The observed hydrolysis rate of M2 was at least ten times higher than that of ENT and d3-ENT in rat plasma. CONCLUSION: ENT was mainly metabolized through the "parent→M2→M1" pathway based on in vitro and in vivo elimination behavior. The observed in vitro deuterium isotope effect translated into increased exposure of the deuterated analog in rats. Once the carbon-hydrogen was replaced with carbon-deuterium (C-D) bonds, the major metabolic pathway was retarded because of the relatively stable C-D bonds. The systemic exposure to d3-ENT can increase in humans, so the dose requirements can be reduced appropriately.

Targeting human central nervous system protein kinases: An isoform selective p38αMAPK inhibitor that attenuates disease progression in Alzheimer's disease mouse models.

The first kinase inhibitor drug approval in 2001 initiated a remarkable decade of tyrosine kinase inhibitor drugs for oncology indications, but a void exists for serine/threonine protein kinase inhibitor drugs and central nervous system indications. Stress kinases are of special interest in neurological and neuropsychiatric disorders due to their involvement in synaptic dysfunction and complex disease susceptibility. Clinical and preclinical evidence implicates the stress related kinase p38αMAPK as a potential neurotherapeutic target, but isoform selective p38αMAPK inhibitor candidates are lacking and the mixed kinase inhibitor drugs that are promising in peripheral tissue disease indications have limitations for neurologic indications. Therefore, pursuit of the neurotherapeutic hypothesis requires kinase isoform selective inhibitors with appropriate neuropharmacology features. Synaptic dysfunction disorders offer a potential for enhanced pharmacological efficacy due to stress-induced activation of p38αMAPK in both neurons and glia, the interacting cellular components of the synaptic pathophysiological axis, to be modulated. We report a novel isoform selective p38αMAPK inhibitor, MW01-18-150SRM (=MW150), that is efficacious in suppression of hippocampal-dependent associative and spatial memory deficits in two distinct synaptic dysfunction mouse models. A synthetic scheme for biocompatible product and positive outcomes from pharmacological screens are presented. The high-resolution crystallographic structure of the p38αMAPK/MW150 complex documents active site binding, reveals a potential low energy conformation of the bound inhibitor, and suggests a structural explanation for MW150's exquisite target selectivity. As far as we are aware, MW150 is without precedent as an isoform selective p38MAPK inhibitor or as a kinase inhibitor capable of modulating in vivo stress related behavior.

Evidence for a large conductance voltage gated cationic channel in rough endoplasmic reticulum of rat hepatocytes.

In this work, we report the single channel characterization of a voltage gated cationic channel from rough endoplasmic reticulum (RER) membranes of rat hepatocytes incorporated into a planar lipid bilayer. The channel was found to be cation selective with a main conductance of 598+/-20 pS in 200 mM KCl cis/50 mM KCl trans. The channel open probability appeared voltage dependent with a voltage for half activation (V(1/2)) of 38 mV and an effective gating charge z of -6.66. Adding either 4-AP (5 mM) or ATP (2.5 mM) to the side corresponding to the cell internal medium caused a strong inhibition of the channel activity. This channel is likely to be involved in maintaining proper cation homeostasis in the RER of hepatocytes.

Defensive nature of Sargassum polycystum (Brown alga) against acetaminophen-induced toxic hepatitis in rats: role of drug metabolizing microsomal enzyme system, tumor necrosis factor-alpha and fate of liver cell structural integrity.

AIM: To assess the defensive nature of Sargassum polycystum (S. polycystum) (Brown alga) against acetaminophen (AAP)-induced changes in drug metabolizing microsomal enzyme system, tumor necrosis factor (TNF-alpha) and fine structural features of the liver during toxic hepatitis in rats. METHODS: Male albino Wistar strain rats used for the study were randomly categorized into 4 groups. Group I consisted of normal control rats fed with standard diet. Group II rats were administered with acetaminophen (800 mg/kg body weight, intraperitoneally). Group III rats were pre-treated with S. polycystum extract alone. Group IV rats were orally pre-treated with S. polycystum extract (200 mg/kg body weight for 21 d) prior to acetaminophen induction (800 mg/kg body weight, intraperitoneally). Serum separated and liver was excised and microsomal fraction was isolated for assaying cytochrome P450, NADPH Cyt P450 reductase and b(5). Serum TNF-alpha was detected using ELISA. Fine structural features of liver were examined by transmission electron microscopy. RESULTS: Rats intoxicated with acetaminophen showed considerable impairment in the activities of drug metabolizing microsomal enzymes, such as cytochrome P450, NADPH Cyt P450 reductase and b(5) when compared with the control rats. The rats intoxicated with acetaminophen also significantly triggered serum TNF-alpha when compared with the control rats. These severe alterations in the drug metabolizing enzymes were appreciably prevented in the rats pretreated with S. polycystum. The rats pretreated with S. polycystum showed considerable inhibition in the elevation of TNF-alpha compared to the rats intoxicated with acetaminophen. The electron microscopic observation showed considerable loss of structural integrity of the endoplasmic reticulum, lipid infiltration and ballooning of mitochondria in the acetaminophen-intoxicated rats, whereas the rats treated with S. polycystum showed considerable protection against acetaminophen-induced alterations in structural integrity. CONCLUSION: These observations suggest that the animals treated with S. polycystum extract may have the ability to protect the drug metabolizing enzyme system and mitochondrial functional status from free radical attack, thereby showing its defense mechanism in protecting hepatic cells from acetaminophen toxic metabolite N-acetyl-para-benzoquinone-imine (NAPQI).

Pathways involved in trifluoperazine-, dibucaine- and praziquantel-induced hemolysis.

This work elucidates differences in the hemolytic pathway developed by the antipsychotic trifluoperazine (TFP), the local anesthetic dibucaine (DBC) and the antihelminthic praziquantel (PZQ). Their partition coefficients (P) were measured at pH 7.4 between n-octanol, microsomes, liposomes, erythrocyte ghosts and n-octanol/water. The effective drug:lipid molar ratios for the onset of membrane solubilization (ReSAT) and complete hemolysis (ReSOL) were calculated from the experimental P values and compared with a classical surface-active compound treatment Lichtenberg, D. Biochim. Biophys. Acta 821 (1985) 470-478[. The contribution of charged/uncharged forms of TFP and DBC for the hemolytic activity was also analyzed. In all cases the hemolytic phenomena could be related to the monomeric drug insertion into the membrane. Only for TFP at isosmotic condition lysis occurs at concentrations beyond the CMC of the drug, indicating that micellization facilitates TFP hemolytic effect, while DBC and PZQ reach a real membrane saturation at their monomeric form.

Cholesterol induced variations of membrane dynamics related to the induction of apoptosis in mouse thymocytes.

PURPOSE: To evaluate the involvement of cholesterol induced variations of membrane dynamics in mouse thymocyte apoptosis. MATERIALS AND METHODS: Membranes of thymocytes of RK mice were enriched with cholesterol using methyl-beta-cyclodextrins as carriers. Spontaneous apoptosis was compared with apoptosis induced either by X-irradiation, by treatment with dexamethasone (DEX), and by phorbol-12-myristate-13-acetate (PMA). Apoptotic cells were quantified by means of flow cytofluorometry. RESULTS: Small amounts of incorporated cholesterol enhance the cellular sensitivity for spontaneous apoptosis whereas larger amounts of incorporated cholesterol protect against spontaneous apoptosis and apoptosis induced by irradiation, DEX, or PMA. CONCLUSIONS: Cholesterol exerts specific rigidity effects on lipid membranes which have been shown to be involved in thymocyte apoptosis. The general effect of higher concentrations of cholesterol protecting against apoptosis hints towards a central protective mechanism. This study believes that either cholesterol paralyses great parts of the cell metabolism or that the apoptotic chain reaction is interrupted at a central point due to protection of membrane lipid regions from oxidative stress.

Diastereospecific kinetics of nicotine N'-oxidation in rat liver microsomes.

1. In kinetic studies, both Eadie-Hofstee plots for cis- and trans-nicotine-1'-N-oxide formation from nicotine in rat liver microsomes were linear. For the formation of cis- and trans-nicotine-1'-N-oxide, the apparent K(m) were 0.240 +/- 0.069 and 1.524 +/- 0.951 mM respectively. Corresponding Vmax were 1.52 +/- 0.48 and 1.19 +/- 0.74 nmol/mg/min respectively. 2. The formation of cis-nicotine-1'-N-oxide was greater than the formation of trans-nicotine-1'-N-oxide in rat liver microsomes and the intrinsic clearance of cis-nicotine-1'-N-oxide formation was 8.1-fold greater than that of trans-nicotine-1'-N-oxide formation. 3. The formation of both cis- and trans-nicotine-1'-N-oxide in rat liver microsomes was inhibited by the addition of 1-(1-naphthyl)-2-thiourea or by heat-treatment of microsomes. 2-Diethylaminoethyl-2, 2-diphenylvalerate (SKF525A) and carbon monoxide did not affect these activities even at high concentrations. 4. Formations of cis- and trans-nicotine-1'-N-oxide correlated significantly with each other (r = 0.862, p < 0.01). These results suggested that the same flavin-containing monooxygenase (FMO) isoform is responsible for the formation of cis- and trans-nicotine-1'-N-oxide in rat liver.

Melatonin enhances tamoxifen's ability to prevent the reduction in microsomal membrane fluidity induced by lipid peroxidation.

The indoleamine melatonin and the synthetic antiestrogenic drug tamoxifen seem to have similar mechanisms in inhibiting the growth of estrogen receptor positive breast cancer cells. In this study, we compared the ability of these molecules, alone and in combination, in stabilizing microsomal membranes against free radical attack. Hepatic microsomes were obtained from male rats and incubated with or without tamoxifen (50-200 microM), melatonin (1 mM) or both; lipid peroxidation was induced by addition of FeCl3, NADPH and ADP. After oxidative damage, membrane fluidity, measured by fluorescence polarization techniques, decreased whereas malonaldehyde (MDA) and 4-hydroxyalkenals (4-HDA) concentrations increased. Incubation of the microsomes with tamoxifen prior to exposure to free radical generating processes inhibited, in a dose-dependent manner, the increase in membrane rigidity and the rise in MDA + 4-HDA levels. When melatonin was added, the efficacy of tamoxifen in preventing membrane rigidity was enhanced. Thus, the IC50s for preventing membrane rigidity and for inhibiting lipid peroxidation obtained for tamoxifen in the presence of melatonin were lower than those obtained with tamoxifen alone. Moreover, tamoxifen (50-200 microM) in the presence of melatonin reduced basal membrane fluidity and MDA + 4-HDA levels in microsomes. These synergistic effects of tamoxifen and melatonin in stabilizing biological membranes may be important in protecting membranes from free radical damage.

A physiologically based pharmacokinetic (PB-PK) model for 1,2-dichlorobenzene linked to two possible parameters of toxicity.

A physiologically based pharmacokinetic (PB-PK) model was developed for 1,2-dichlorobenzene (1,2-DCB) for the rat. This model was adjusted for the human situation, using human in vitro parameters, including a Vmax and Km determined with human microsomes. For comparison, the Vmax and Km values from the rat were scaled allometrically to the human case. The model was used in two ways: (1) Acute hepatotoxicity was related to the amount of reactive metabolites (epoxides) formed in vitro. For rats, the hepatic concentration of epoxide metabolites in vivo after exposure to a toxic dose level (250 mg/kg bw) was predicted using in vitro parameters. For man, the dose level needed to obtain the same toxic liver concentration of reactive metabolites as in rat was predicted, assuming a concentration-effect relationship in the liver. It could be concluded that this concentration is not reached, even after induction of the oxidation step, due to saturation of metabolism and a concomitant accumulation of 1,2-DCB in fat. (2) Hepatotoxicity was related to depletion of glutathione (GSH) in the liver. In the model, the consumption of hepatic GSH by metabolism (based on in vivo and in vitro data) and normal turnover was described. In vivo validation was conducted by comparing the predictions of the model with the results of a GSH depletion study performed at two dose levels (50 and 250 mg/kg bw). Subsequently, the GSH consumption by 1,2-DCB metabolites was estimated for man using human in vitro metabolic data. GSH turnover in human liver was assumed to be the same as that in rat. It appeared that at a dose level of 250 mg/kg, hepatic GSH was completely depleted after 10 hr for man, whereas for the rat a maximum depletion of 75% was predicted, after 15 hr. The presented model provides a quantitative tool for evaluating human risk for two different toxicity scenarios, namely covalent binding of reactive metabolites and depletion of GSH.

Microsomal function in biliary obstructed rats: effects of S-adenosylmethionine.

BACKGROUND/AIMS: S-adenosylmethionine has been reported to have beneficial effects in the treatment of different chronic liver diseases and to protect against different hepatotoxic agents. The aim of this study was to investigate whether S-adenosylmethionine treatment might contribute to improved microsomal function in chronically biliary obstructed rats. METHODS: Secondary biliary cirrhosis was induced by 28 days of bile duct obstruction. Groups of control and cirrhotic animals received S-adenosylmethionine (10 mg/kg per day) through the experimental period. RESULTS: Bile duct obstruction resulted in a marked increase in lipid peroxidation levels and decreases in glutathione concentration, microsomal membrane fluidity, microsomal cytochrome P-450 content, NADPH-cytochrome P-450 reductase activity and the activities of the aniline hydroxylase, aminopyrine demethylase and ethoxycoumarin deethylase. Reductions in glutathione and cytochrome P-450 concentration were not corrected by S-adenosylmethionine, but lipid peroxidation, the decrease in the activities of the various microsomal monooxygenases and the reduction in microsomal membrane fluidity were partially prevented. A significant relationship was found between membrane fluidity and aniline hydroxylase, aminopyrine demethylase or ethoxycoumarin deethylase activities. CONCLUSIONS: S-adenosylmethionine administration partially preserves microsomal function. This effect could be associated to the protection of membrane function by restoring transmethylation reactions.

Bioactivation of estrone and its catechol metabolites to quinoid-glutathione conjugates in rat liver microsomes.

Although the carcinogenic effects of estrogens have been mainly attributed to hormonal properties, there is interest in estrogens acting as chemical carcinogens by binding to cellular macromolecules. In the present study, we explored factors which influence the rate of P450-catalyzed formation of the o-quinones (3,5-cyclohexadiene-1,2-diones) from 2-hydroxyestrone (2-OHE) and 4-hydroxyestrone (4-OHE) as well as from estrone in rat liver microsomes. The initially formed o-quinones were trapped as their GSH conjugates which were separated and characterized by HPLC with electrospray-MS detection. Two mono-GSH conjugates were observed from the 2-OHE-o-quinone as well as a conjugate where GSH had added twice to the molecule producing a di-GSH conjugate. 4-OHE-o-quinone gave only one mono-GSH adduct as well as a di-GSH adduct. Both 2-OHE and 4-OHE were excellent substrates for P450, generating o-quinone GSH adducts at 94 and 40 times, respectively, the rate of estrone. 2-OHE but not 4-OHE saturated P450 at unusually low concentrations (0.2 nmol of P450/mL) perhaps due to differences in the stability of the o-quinones formed in the active site of the enzyme. Preliminary data suggest that the o-quinones of both 2-OHE and 4-OHE could isomerize to quinone methides (4-alkyl-2,5-cyclohexadien-1-ones, QMs). The o-quinones of the catechol estrogens were incubated at 37 degrees C (pH 7.4) in the absence of GSH. Aliquots were removed at various times and combined with GSH. From the pseudo-first-order rate of disappearance of the o-quinone GSH adducts, the half-lives of the o-quinones were determined. The o-quinone from 2-OHE has a half-life of 42 +/- 3 s at 37 degrees C (pH 7.4), and the o-quinone from 4-OHE has a half-life of 12.2 +/- 0.4 min under identical conditions. The o-quinones of the AB ring analogs of the catechol estrogens (3,4-dihydroxy-5,6,7,8-tetrahydronaphthalene and 1,2-dihydroxy-5,6,7,8-tetrahydronaphthalene) isomerize to QMs, suggesting that a similar reaction pathway could occur with the o-quinones from catechol estrogens. In support of this, oxidation of 4-OHE and quenching with GSH after 70 min produced 9-dehydro-4-hydroxyestrone (3-hydroxy-1,3,5-(10),9(11)-estratetraen-17-one), a product which could result from either the QM hydrolysis product or the QM--glutathione conjugate, both of which could eliminate to give the conjugated alkene of 4-OHE. The implications of the o-quinone/QM pathway to the in vivo effects of catechol estrogens are not known; however, given the direct link between excessive exposure to endogenous estrogens and the enhanced risk of breast cancer, the potential for formation of additional reactive intermediates needs to be explored.

The role of vitamin E in the susceptibility of rat lung and liver microsomes to iron-stimulated peroxidation.

The production of thiobarbituric acid-reactive substances (TBA-RS) and ethane, two markers of the lipid peroxidation process, was evaluated in rat lung and liver microsomal membranes incubated in the presence of either ferrous ions or a mixture of ferric ions and ascorbate. Microsomal fractions isolated from lung tissue were more resistant than those isolated from the liver. Compared to Fe2+, the association of Fe3+/ascorbate seemed to be totally ineffective in stimulating peroxidation of lung microsomes. The fatty acid profile of lung and liver microsomal membranes could not be responsible for their different susceptibility to free radical degradation. The microsomal fraction isolated from lung showed a higher vitamin E concentration than the liver. The importance of vitamin E in protecting lung membranes was assessed by using lung and liver isolated from vitamin E-deficient and vitamin E-supplemented rats. For both lung and liver microsomal fractions an inverse relationship between vitamin E concentrations and the extent of lipid peroxidation was observed. However, although the vitamin E concentrations in lung and liver microsomes isolated from rats submitted to a vitamin E-deficient diet were not different, lung microsomes still exhibited a lower production of TBA-RS and ethane than liver. In addition to vitamin E, other factors must be involved to explain the resistance of lung microsomes to lipid peroxidation.

Effect of dietary antioxidants on the susceptibility to hepatic microsomal lipid peroxidation in the rat.

The inhibitory effect of probucol on ferrous-iron-induced microsomal lipid peroxidation was compared to that of alpha-tocopherol and butylated hydroxytoluene (BHT). Male Wistar rats were fed with diets containing 1% probucol, 0.2% BHT or 0.1% alpha-tocopherol for 30 days. There were no effects of dietary antioxidants on growth parameters, although liver weight was significantly higher in the BHT-fed rats. Probucol reduced serum levels of total and free cholesterol, while BHT feeding increased the concentrations of serum thiobarbituric-acid-reactive substances, HDL cholesterol and hepatic phospholipid. alpha-Tocopherol had no effect on these parameters. Incorporation of both, probucol and alpha-tocopherol, decreased the susceptibility of microsomes to lipid peroxidation in vitro, while BHT incorporation increased hepatic microsomal lipid peroxidation. These results suggest the possible usefulness of probucol for treatment of both hypercholesterolemia and elevated hepatic microsomal lipid peroxidation, while alpha-tocopherol decreases only an elevated lipid peroxidation. BHT works as a prooxidant.

A microsomal membrane component associated with iron reduction in NADPH-supported lipid peroxidation.

This study was conducted to determine whether a factor responsible for reduced nicotinamide adenine dinucleotide phosphate (NADPH)-supported lipid peroxidation in rat liver microsomes is involved in iron reduction by cooperation with NADPH-cytochrome P450 reductase. Under anaerobic conditions, NADPH-dependent reduction of ferric pyrophosphate in microsomes was not dependent on cytochrome P450 levels and was not inhibited by carbon monoxide (CO). All of the iron complexes with chelators such as adenosine 5'-diphosphate, pyrophosphate, nitrilotriacetate, oxalate or citrate were reduced in microsomes, although in the reconstituted system containing purified NADPH-cytochrome P450 reductase little or no iron reduction was found. A cytochrome P450-free fraction from a cholate-solubilized preparation of microsomes after passage through a laurate sepharose column was required for reduction of iron pyrophosphate in the reconstituted system leading to lipid peroxidation. The iron reduction was not inhibited by CO and was destroyed by heat treatment or trypsin digestion of the fraction. All iron complexes were reduced in the presence of the fraction, using a reducing equivalent of NADPH via NADPH-cytochrome P450 reductase. The results indicate that a heat-labile component, which is probably a protein distinct from cytochrome P450, is associated with iron reduction responsible for lipid peroxidation in microsomes.

Ethanol-induced oxidative stress and nutritional status.

The ability of dietary ethanol, administered over a 10-day period, to elevate production rates of reactive oxygen species and to alter glutathione levels has been determined in both liver and cerebellum, a brain region known to be susceptible to ethanol-induced damage. Two groups of ethanol-consuming rats were used. One set of treated animals that received an all-liquid ethanol-containing diet experienced weight gain, and this gain was matched in a pair-fed control group. The other ethanol-treated group that had free access only to solid chow and water containing ethanol lost weight during the exposure period. The corresponding control group that received unlimited water and chow was allowed to gain weight normally. In animals that lost weight as a consequence of ethanol in the drinking water, evidence of oxidative stress was enhanced relative to that in animals receiving ethanol by way of the liquid diet. This latter set gained weight, despite higher blood ethanol levels than the group that lost weight. An excess prooxidant condition prevailed in the liver and cerebellum of the ethanol-dosed malnourished group. In the case of liver, this difference may relate to a greater lability of iron-containing proteins in the rats that experienced weight loss, leading to the appearance of low molecular weight iron in the cytosol.

Increased P0 glycoprotein gene expression in primary and transfected rat Schwann cells after treatment with axolemma-enriched fraction.

To elucidate the role of axonal plasma membrane factors in the differentiation of Schwann cells, we investigated the effect of an axolemma-enriched fraction (AEF) isolated from myelinated CNS tissue on the expression of P0 glycoprotein, the major glycoprotein in peripheral myelin, in primary rat Schwann cells (PSC) isolated from sciatic nerve, as well as in a transfected rat Schwann cell line (TSC). AEF increased PO-mRNA levels in PSC and TSC in a concentration-dependent manner, producing a maximal induction of nearly twofold after 48 hr of treatment. A similar induction of P0 mRNA was elicited in TSC by the cAMP-activating agents 8-bromo-cAMP and forskolin, which have been shown to induce myelin proteins in PSC. In addition to inducing P0 mRNA, AEF and forskolin also increased the amount of P0 protein in TSC, as indicated by increased P0-immunoreactive staining. However, in TSC, axolemma caused no increase in expression of CAT linked to a P0 promoter while forskolin caused a marked increase in the expression from the P0 promoter. These results suggest that AEF, in contrast to forskolin, does not regulate P0-mRNA expression at the level of transcriptional activity. These in vitro systems may be useful for the study of axolemmal factors that induce Schwann cell differentiation.

A possible mechanism of iron neurotoxicity.

Iron-dependent microsomal lipid peroxidation and catechol-iron (copper)-induced lipid peroxidation have been studied to prove possible nigrostriatal cell damage. Iron-dependent microsomal lipid peroxidation could be initiated by reduced irons coordinated with phosphate moieties in the membranes and significantly inhibited by copper salicylate (hydrophobic and permeable O2-scavenger) and desferrioxamine (a powerful iron-chelating agent), but not by SOD. Ferric or cupric ion significantly promoted a peroxidative cleavage in liposomes (model membranes) after coordinating with dopa or dopamine. Either alpha-tocopherol or desferrioxamine completely abolished the dopa-Fe3+ complex-induced phospholipid peroxidation, while SOD, catalase or sodium benzoate did not. A ferroxidase, ceruloplasmin, significantly inhibited the lipid peroxidation induced by the dopa-Fe3+ complex, indicating the importance of the reduction of iron moiety in the complex for the lipid peroxidation. On the basis of the results obtained with these model systems, nigrostriatal damage by iron had been discussed.

Prevention of carbon tetrachloride-induced liver necrosis by the chelator alizarin sodium sulfonate.

The administration of the calcium chelator alizarin sodium sulfonate (ASR) (100 mg/kg ip in saline) 30 min before or 6 or 10 hr after CCl4 (1 ml/kg ip as a 20% v/v solution in olive oil) partially prevents the necrogenic effect of the hepatotoxin at 24 hr, but prevention of CCl4 fat accumulation was not observed. Protective action cannot be attributed to potential decreasing effects of ASR on CCl4 levels reaching the liver, on the covalent binding of CCl4-reactive metabolites to cellular components, or on CCl4-induced lipid peroxidation because ASR does not modify these parameters significantly. ASR administration increases GSH levels in livers of both control and CCl4-poisoned animals and decreases the calcium content of intoxicated animals at 24 hr of poisoning. ASR significantly lowers the body temperature of CCl4-treated animals at different times of the intoxication process. Present and previous results from our laboratory on the preventive effects of another very specific calcium chelator, calcion, and several anticalmodulins suggest that the beneficial effects of ASR might be associated with its calcium chelating ability. Other protective effects of ASR, such as lowering body temperature or increasing GSH content in liver, cannot be excluded.

Fluidificacion de la membrana microsomal hepatica y su relacion con el envejecimiento / Fluidity of hepatic microsomal membrane and its relation with aging

El efecto del envejecimiento sobre la composición fosfolipídica de la membrana hepática fue estudiada en dos grupos de ratas Wistar jóvenes (2 meses) y maduros (6 meses). Cuando fue analizado el contenido fosfolipídico microsomal total, el grupo de ratas maduras mostró un incremento significativo (73%). El patrón fosfolipídico microsomal también mostró un comportamiento diferente en ambos grupos, con un significativo incremento en fosfatidilcolina (62%), fosfatidilserina (124%), fosfatidilinositol (31%) y esfingomielina (10%) y aparente en fosfatidiletanolemina y fosfatidilglicerol en el grupo de 6 meses. Una elevada fluidificación de la membrana microsomal en animales añosos fue relevado por un incremento en el índice PC/EM (47%). Este incremento en la fluidificación durante el proceso de envejecimiento puede reflejar una respuesta adaptativa resultante en cambio en la actividad enzimática responsable del metabolismo de drogas y carcinógenos

[Fluidity of hepatic microsomal membrane and its relation with aging]. / Fluidificación de la membrana microsomal hepática y su relación con el envejecimiento.

The effect of aging on hepatic microsomal membrane phospholipid composition was studied composition was studied in both young (2 months) and mature (6 months) Wistar rats. When total microsomal phospholipid content was analysed the aged group showed a significant increment (73%). Microsomal phospholipid pattern also showed a different behavior between both groups, with a significative increase in phosphatidylcholine (62%), phosphatidylserine (124%), phosphatidylinositol (31%) and sphingomyelin (10%) and appearance of phosphatidylethanolamine and phosphatidylglycerol in the six-month group. A higher microsomal membrane fluidity in the aged animals was revealed by the increase in PC/EM index (47%). This increment jin fluidity during aging process may reflect an adaptative response resulting in changes on the enzyme activities responsible for drug and carcinogen metabolism.