Curcumin encapsulated in chitosan nanoparticles: a novel strategy for the treatment of arsenic toxicity

Water-soluble nanoparticles of curcumin were synthesized, characterized and applied as a stable detoxifying agent for arsenic poisoning. Chitosan nanoparticles of less than 50 nm in diameter containing curcumin were prepared. The particles were characterized by TEM, DLS and FT-IR. The therapeutic efficacy of the encapsulated curcumin nanoparticles (ECNPs) against arsenic-induced toxicity in rats was investigated. Sodium arsenite (2mg/kg) and ECNPs (1.5 or 15 mg/kg) were orally administered to male Wistar rats for 4 weeks to evaluate the therapeutic potential of ECNPs in blood and soft tissues. Arsenic significantly decreased blood δ-aminolevulinic acid dehydratase (δ-ALAD) activity, reduced glutathione (GSH) and increased blood reactive oxygen species (ROS). These changes were accompanied by increases in hepatic total ROS, oxidized glutathione, and thiobarbituric acid-reactive substance levels. By contrast, hepatic GSH, superoxide dismutase and catalase activities significantly decreased on arsenic exposure, indicative of oxidative stress. Brain biogenic amines (dopamine, norepinephrine and 5-hydroxytryptamine) levels also showed significant changes on arsenic exposure. Co-administration of ECNPs provided pronounced beneficial effects on the adverse changes in oxidative stress parameters induced by arsenic. The results indicate that ECNPs have better antioxidant and chelating potential (even at the lower dose of 1.5 mg/kg) compared to free curcumin at 15 mg/kg. The significant neurochemical and immunohistochemical protection afforded by ECNPs indicates their neuroprotective efficacy. The formulation provides a novel therapeutic regime for preventing arsenic toxicity.     

Combined administration of N-acetylcysteine and monoisoamyl DMSA on tissue oxidative stress during arsenic chelation therapy

The present study deals with the therapeutic potential of combined administration of N-acetylcysteine (NAC) along with monoisoamyl DMSA (MiADMSA) against chronic arsenic poisoning in guinea pigs. Animal were exposed to 50 ppm arsenic in drinking water for 8 mo and subsequently treated for 5 consecutive days with 100 mg/kg NAC (orally) and MiADMSA (intraperitoneally), individually or in combination (50 mg/kg each). Arsenic exposure produced a significant depletion of blood δ-aminolevulinic acid dehydrate (ALAD) activity, increased the blood zinc protoporphyrin (ZPP) level, and reduced blood and liver glutathione (GSH) levels in guinea pigs. Hepatic oxidized glutathione (GSSG) and thiobarbituric acid reactive substance (TBARS) levels showed a marked increase, whereas hepatic alkaline phosphatase (ALP) activity decreased and acid phosphatase (ACP) activity increased on arsenic exposure. Significant depletion of liver transaminase activities on arsenic exposure suggests organ injury. Administration of MiADMSA, alone and in combination with NAC after arsenic exposure, was able to significantly enhance hepatic GSH and to reduce GSSG and TBARS levels compared to the arsenic control. Biochemical variables indicative of liver injury generally remained insensitive to any of these treatments. The recoveries in parameters indicative of oxidative stress were more marked in guinea pigs treated with combined administration of NAC and MiADMSA than monotherapy. Interestingly, there was a more pronounced depletion of arsenic from blood and tissues after combined treatment with NAC plus MiADMSA than MiADMSA. Blood and tissues copper, zinc, iron, and calcium concentrations showed a significant increase after arsenic exposure, which showed improvement, particularly after combined administration of MiADMSA and NAC. Based on these data, a proposal can be made that greater effectiveness in chelation treatment against chronic arsenic poisoning (i.e., turnover in the oxidative stress and removed of arsenic from the system) could be achieved by combined administration of an antioxidant (preferably having a thiol moiety) with MiADMSA.     

Combined administration of iron and monoisoamyl-DMSA in the treatment of chronic arsenic intoxication in mice

Co-administration of iron in combination with monoisoamyl dimercaptosuccinic acid (MiADMSA) against chronic arsenic poisoning in mice was studied. Mice preexposed to arsenic (25 ppm in drinking water for 6 months) mice were treated with MiADMSA (50 mg/kg, intraperitoneally) either alone or in combination with iron (75 or 150 mg/kg, orally) once daily for 5 days. Arsenic exposure led to a significant depletion of blood δ-aminolevulinic acid dehydratase (ALAD) activity, hematocrit, and white blood cell (WBC) counts accompanied by small decline in blood hemoglobin level. Hepatic reduced glutathione (GSH) level, catalase and superoxide dismutase (SOD) activities showed a significant decrease while, oxidized glutathione (GSSG) and thiobarbituric acid-reactive substances (TBARS) levels increased on arsenic exposure, indicating arsenic-induced hepatic oxidative stress. Liver aspartate and alanine transaminases (AST and ALT) activities also decreased significantly on arsenic exposure. Kidney GSH, GSSG, catalase level and SOD activities remained unchanged, while, TBARS level increased significantly following arsenic exposure. Brain GSH, glutathione peroxidase (GPx), and SOD activities decreased, accompanied by a significant elevation of TBARS level after chronic arsenic exposure. Treatment with MiADMSA was marginally effective in reducing ALAD activity, while administration of iron was ineffective when given alone. Iron when co-administered with MiADMSA restored blood ALAD activity. Administration of iron alone had no beneficial effects on hepatic oxidative stress, while in combination with MiADMSA it produced significant decline in hepatic TBARS level compared to the individual effect of MiADMSA. Renal biochemical variables were insensitive to any of the treatments. Combined administration of iron with MiADMSA also had no additional beneficial effect over the individual protective effect of MiADMSA on brain oxidative stress. Interestingly, combined administration of iron with MiADMSA provided more pronounced depletion of blood arsenic, while no additional beneficial effects on tissue arsenic level over the individual effect of MiADMSA were noted. The results lead us to conclude that iron supplementation during chelation has some beneficial effects particularly on heme synthesis pathway and blood arsenic concentration.     

Response of lead-induced oxidative stress and alterations in biogenic amines in different rat brain regions to combined administration of DMSA and MiADMSA

The present study was planned to investigate if combined administration of meso-2,3-dimercaptosuccinic acid (DMSA) and monoisoamyl DMSA (MiADMSA) could achieve better recovery in the altered biochemical parameters suggestive of brain oxidative stress and depletion of lead from blood and brain following acute lead exposure. Male Wistar rats were exposed to lead nitrate (50 mg/kg, i.p., once daily for 5 days) followed by treatment with the above chelating agents using two different doses of 25 or 50 mg/kg (orally) either alone and in combination once daily for five consecutive days. Lead exposure resulted in the significant inhibition of δ-aminolevulinic acid dehydratase activity and depletion of glutathione (GSH) in blood. These changes were accompanied by significant reduction in blood hemoglobin, RBC levels and superoxide dismutase and catalase activities. Significant increase in blood reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) levels were noted. We observed marked increase in brain ROS level while GSH/oxidized glutathione ratio showed significant decrease accompanied by a significant increase in blood and brain lead concentration. The levels of norepinephrine, dopamine and serotonin in different brain regions were also altered on lead exposure. Co-administration of DMSA and MiADMSA particularly at the lower dose was most effective in the recovery of lead-induced changes in the hematological variables and oxidative stress and resulted in more pronounced depletion of lead from blood and brain compared to monotherapy with these chelators. On the other hand, combined administration of MiADMSA (50 mg/kg) in combination with DMSA (25 mg/kg each) had additional beneficial effect over the individual effect of chelating agent in the recovery of altered levels of brain biogenic amines. The study suggests that administration of MiADMSA is generally a better lead chelator than DMSA while combined administration of DMSA and MiADMSA might be a better treatment option compared to monotherapy at least in the removal of lead from the target tissues.     

Interactive effect of arsenic and fluoride on cardio-respiratory disorders in male rats: possible role of reactive oxygen species

Epidemiological evidence demonstrates positive correlation between environmental and occupational arsenic or fluoride exposure and risk to various cardio-respiratory disorders. Arsenic-exposure has been associated with atherosclerosis, hypertension, cerebrovascular diseases, ischemic heart disease, and peripheral vascular disorders, whereas Fluoride-exposure manifests cardiac irregularities and low blood pressure (BP). Present study aims to study the combined effects of these toxicants on various cardio-respiratory variables in male rats. Single intravenous (i.v.) dose of arsenic (1, 5, 10 mg/kg) or fluoride (5, 10, 20, 36.5 mg/kg) either alone or in combination were administered. Individual exposure to arsenic or fluoride led to a significant depletion of mean arterial pressure, heart rate (HR), respiration rate and neuromuscular (NM) transmission in a dose-dependent manner. These changes were accompanied by increased levels of blood reactive oxygen species (ROS) and decreased glutathione (GSH) concentrations. An increase in the blood acetyl cholinesterase (AChE) activity was observed in both arsenic or fluoride exposed rats. These changes were significantly more pronounced in arsenic-exposed animals than in fluoride. During combined exposure to arsenic (5 mg/kg) + fluoride (20 mg/kg) or arsenic (10 mg/kg) + fluoride (36.5 mg/kg) the toxic effects were more pronounced compared to individual toxicities of arsenic or fluoride alone. However, combined exposure to arsenic (5 mg/kg) + fluoride (36.5 mg/kg) resulted in antagonistic effects on variables suggestive of altered cardio-respiratory function and oxidative stress. The results from the present study suggest that arsenic or fluoride individually demonstrate cardio-respiratory failure at all doses whereas during combination exposure these toxins show variable toxicities; both synergistic and antagonistic effects depending upon the dose. Moreover, it may be concluded that arsenic and/or fluoride cardio-respiratory toxicity may be mediated via oxidative stress. However, these results are new in the discipline thus requires further exploration.     

Role of combined administration of Tiron and glutathione against aluminum-induced oxidative stress in rat brain.

The current study was carried out to investigate the potential role of 4,5 dihydroxy benzene 1,3 disulfonic acid di sodium salt (Tiron) and glutathione (GSH) either individually or in combination against aluminum (Al)-induced toxicity in Wistar rats. Animals were exposed to aluminum chloride at a dose of 172.5mg/kg/d orally for 10 weeks. Tiron and GSH were administered at a dose of 471-mg/kg/d i.p. and 100mg/kg/d orally, respectively, for 7 consecutive days. Tiron is a diphenolic chelating compound which forms water soluble complexes with a large number of metal ions. Induction of oxidative stress was recorded in brain and serum after Al exposure. Significant decrease was recorded in reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GP(x)), catalase (CAT), superoxide dismutase (SOD), acetyl cholinesterase (AChE) and an increase was observed in thiobarbituric acid reacting substance (TBARS) and glutathione-S-transferase (GST) in brain and serum. Most of the above parameters responded positively to individual therapy with Tiron, but more pronounced beneficial effects on the above-described parameters were observed when Tiron was administered in combination with GSH. Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) studies also showed significantly high concentration of Al in brain and blood. Tiron was slightly more effective then GSH in reducing the concentration of Al from the brain and blood, however, no further improvement was recorded when Tiron was administered in combination with GSH in reducing the concentration of Al.     

Preventive Efficacy of Bulk and Nanocurcumin Against Lead-Induced Oxidative Stress in Mice

Chronic lead exposure is associated with several health disorders in humans and animals. Lead exposure leads to the generation of reactive oxygen species and depletes body antioxidant enzymes causing damage to various macromolecules and ultimately cell death. Curcumin has been widely recognized to protect against metal toxicity but has major limitations of reduced bioavailability. Nanoencapsulation of curcumin could be an effective strategy to combat lead induced toxic manifestations. The present study investigates the protective efficacy of bulk and nanocurcumin against lead-induced toxicity. Swiss albino mice were daily exposed to lead acetate (25 mg/kg, i.p.) alone and after 1 h treated either with curcumin (15 mg/kg, orally) or nanocurcumin (15 mg/kg, orally) for two consecutive weeks. The preventive efficacy of nanocurcumin was evaluated against various altered biochemical variables suggestive of oxidative stress and lead accumulation in blood and soft tissues. Coadministration of nanocurcumin with lead restored the altered δ-aminolevulinic acid dehydratase activity, glutathione (reduced and oxidized) levels, and also decreased reactive oxygen species, and thiobarbituric acid reactive substances levels. Nanocurcumin due to its possible chelating property and enhanced bioavailability efficiently removed lead from blood and soft tissues compared to bulk curcumin. Results demonstrate the enhanced preventive efficacy of nanocurcumin and suggest an interesting and novel approach for better treatment of lead toxicity.     

The role of the glutathione system in seizures induced by diphenyl diselenide in rat pups

The present study investigated the role of the glutathione system in seizures induced by diphenyl diselenide (PhSe)₂ (50 mg/kg) in rat pups (post natal day, 12–14). Reduced glutathione (GSH) (300 nmol/site; i.c.v.), administered 20 min before (PhSe)₂, abolished the appearance of seizures, protected against the inhibition of catalase and δ-aminolevulinic dehydratase (δ-ALA-D) activities and increased glutathione peroxidase (GPx) activity induced by (PhSe)₂. Administration of l-buthionine sulfoximine (BSO, a GSH-depleting compound) (3.2 μmol/site; i.c.v.) 24 h before (PhSe)₂ increased the percentage (42–100%) of rat pups which had seizure episodes, reduced the onset for the first convulsive episode. In addition, BSO increased thiobarbituric acid reactive species (TBARS) levels and decreased GSH content, catalase, δ-ALA-D and Na⁺, K⁺-ATPase activities. Treatment with sub effective doses of GSH (10 nmol/site) and d-2-amino-7-phosphonoheptanoic acid (AP-7, an antagonist of the glutamate site at the NMDA receptor; 5 mg/kg, i.p.) abolished the appearance of seizures induced by (PhSe)₂ in rat pups. Sub effective doses of GSH and kynurenic acid (an antagonist of strychnine-insensitive glycine site at the NMDA receptor; 40 mg/kg, i.p.) were also able in abolishing the appearance of seizures induced by (PhSe)₂. In conclusion, administration of GSH protected against seizure episodes induced by (PhSe)₂ in rat pups by reducing oxidative stress and, at least in part, by acting as an antagonist of glutamate and glycine modulatory sites in the NMDA receptor.     

Protective effect of various antioxidants on the toxicity of sulphur mustard administered to mice by inhalation or percutaneous routes

Protective effect of various antioxidants, trolox (water soluble analogue of vitamin E), quercetin (bioflavonoid) and glutathione reduced (GSH), was studied following sulphur mustard (SM) intoxication. SM, a blistering agent was administered to Swiss albino female mice through inhalation (1 LC50=42.3 mg/m3 for 1 h duration; 14 days observation for mortality) and percutaneous (1 LD50=154.7 mg/kg; 7 days observation for mortality) routes. The antioxidants were administered three times at the dose of trolox, 500 microg/kg; quercetin, 5 mg/kg and GSH, 400 mg/kg body weight by intraperitoneal injection, one immediately following SM exposure, then once each day for 2 days after SM treatment. The effect of antioxidants on survival, markers of oxidative damage and purine metabolites was investigated. Survival study animals were observed for 14 days. Oxidative markers (in blood, liver and lung) and purine metabolites (in blood and urine) were investigated 72 h after SM treatment. Survival time increased significantly following trolox and quercetin treatments through the inhalation route. Significant decrease in GSH and increase in the level of malondialdehyde (MDA) indicated oxidative damage to liver and lung tissues following SM inhalation and percutaneous exposure. Blood and urinary uric acid, end product of purine metabolism showed an increased following both routes of exposures. The antioxidants, trolox and quercetin protected the liver and lung tissues from oxidative damage caused by SM exposure through inhalation and percutaneous routes. This study showed that antioxidants could enhance survival time, protect liver and lung from oxidative damage and reduce accumulation of purine metabolites in blood following SM intoxication.     

Studies on the mechanism of haloacetonitrile-induced gastrointestinal toxicity: interaction of dibromoacetonitrile with glutathione and glutathione-S-transferase in rats

The haloacetonitrile, dibromoacetonitrile (DBAN), is a direct-acting genotoxic agent that has been detected in drinking water. In a time course study, male Sprague-Dawley rats were treated with DBAN (75 mg/kg PO), and killed at 0.5, 1, 2, and 4 hr after treatment. In a dose response study, animals were treated orally with various doses of DBAN (25, 50, 75, and 100 mg/kg) and killed at one-half hour after treatment. Control animals received 1 ml/kg PO of the vehicle dimethyl sulfoxide (DMSO). In both experiments blood and organs were collected and stored at -80 degrees C until the time of analysis. At 0.5 hr after treatment, a single oral dose of DBAN caused a significant decrease of glutathione (GSH) concentrations in liver (54% of control) and stomach (6% of control). Hepatic GSH depletion was maximal at 0.5 hr and rebound to the control levels by 4 hr. In contrast, gastric GSH concentrations remained low at all time points. DBAN caused an insignificant change in both kidney and blood GSH levels. DBAN significantly inhibited glutathione-S-transferase (GST) activity in liver and stomach. Hepatic GST inhibition was maximal (34% of control) at 2 hr and minimal (80% of control) at 4 hr. Meanwhile, in the stomach GST activity was inhibited at 1 hr (60% of control) and remained low at all times after treatment. Both GSH depletion and GST inhibition were dose-dependent. This study indicates that GSH and GST play an important role in the metabolism and detoxification of DBAN in rats. The prolonged depletion of GSH and inhibition of GST in the gastrointestinal (GI) tissues suggest that the GI tract is a major target for DBAN toxicity.     

δ-aminolevulinic acid transport and synthesis,porphyrin synthesis and heme catabolism in chick embryo liver and heart cells

Liver and heart represent two organs with markedly different needs for heme as related to their metabolic roles. To examine these diferences chick embryo heart and liver cells were compared with respect to transport of δ-aminolevulinic acid and activity of δ-aminolevulinic acid synthetase, porphyrin synthesis and heme oxygenase. Heart cells were found to have a low rate of δ-aminolevulinic acid uptake, a high resting level of δ-aminolevulinic acid synthetase activity and a lower level of heme oxygenase activity as compared with liver cells. The hepatic cell uptake of δ-aminolevulinic acid was 6–25-times that of heart cells. The embryonal heart cell appears to be a balanced autonomous system for the synthesis and degradation of heme. The embryonal liver cell represents a cell system permeable to exogenous δ-aminolevulinic acid, which is also responsive to and inducible by external stimuli.     

Antioxidant levels in the rat brain after nitric oxide synthase inhibition: a preliminary report

Protective effects of NOS inhibitors and free radical scavengers in cerebral ischemia are well documented. The present study was undertaken to determine the possible effects of NOS inhibition on brain antioxidants. Levels of both enzymatic [glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD)] and non-enzymatic [reduced glutathione (GSH)] antioxidants following nitric oxide synthase (NOS) inhibition by N(G)-nitro-L-arginine methyl ester (L-NAME), D-NAME or 7-nitroindazole (7-NI) have been investigated. NOS activity and antioxidant levels in the rat cerebellum and medulla were estimated 1 h after treatment with L-NAME (10, 30 and 100 mg/kg, i.p.), D-NAME (100 mg/kg, i.p.) or 7-NI (25 mg/kg, i.p.). L-NAME and 7-NI inhibited NOS activity in a dose-dependent manner. D-NAME also exhibited significant NOS inhibition. The activity of SOD and the GSH level remained unaltered following NOS inhibition. However, L-NAME and D-NAME at 100 mg/kg attenuated GPx activity in the cerebellum, though 7-NI had no effect. L-NAME inhibited catalase activity in medulla only at 30 mg/kg, but had no effect in cerebellum. However, 7-NI (25 mg/kg), D-NAME and L-NAME at 100 mg/kg did not affect catalase activity in the rat brain. Thus, NOS inhibition by the three agents did not have major effects on brain antioxidant levels.     

Antioxidant levels in the rat brain after nitric oxide synthase inhibition: a preliminary report

Abstract

Protective effects of NOS inhibitors and free radical scavengers in cerebral ischemia are well documented. The present study was undertaken to determine the possible effects of NOS inhibition on brain antioxidants. Levels of both enzymatic [glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD)] and non-enzymatic [reduced glutathione (GSH)] antioxidants following nitric oxide synthase (NOS) inhibition by N^G-nitro-L-arginine methyl ester (L-NAME), D-NAME or 7-nitro-indazole (7-NI) have been investigated. NOS activity and antioxidant levels in the rat cerebellum and medulla were estimated 1 h after treatment with L-NAME (10, 30 and 100 mg/kg, i.p.), D-NAME (100 mg/kg, i.p.) or 7-NI (25 mg/kg, i.p.). L-NAME and 7-NI inhibited NOS activity in a dose-dependent manner. D-NAME also exhibited significant NOS inhibition. The activity of SOD and the GSH level remained unaltered following NOS inhibition. However, L-NAME and D-NAME at 100 mg/kg attenuated GPx activity in the cerebellum, though 7-NI had no effect. L-NAME inhibited catalase activity in medulla only at 30 mg/kg, but had no effect in cerebellum. However, 7-NI (25 mg/kg), D-NAME and L-NAME at 100 mg/kg did not affect catalase activity in the rat brain. Thus, NOS inhibition by the three agents did not have major effects on brain antioxidant levels.     

Inhibition of δ-aminolevulinic acid synthetase and δ-aminolevulinic acid dehydrase by L-2-amino-4-methoxy-trans-3-butenoic acid in the rat

The rate limiting enzyme of heme biosynthesis, δ-aminolevulinic acid synthetase (ALA synthetase), and the second enzyme in the heme biosynthetic pathway, δ-aminolevulinic acid dehydrase (ALA dehydrase), were inhibited by the olefinic amino acid L-2-amino-4-methoxy - $\text{trans}$-3-butenoic acid (AMTB). Administration of AMTB (20 mg/kg; i.p.) to rats inhibited ALA synthetase and ALA dehydrase in control animals and in animals with markedly elevated activity of ALA synthetase which resulted from the administration of 3,5-dicarbethoxy-1,4-dimethyl-collidine (DDC, 200 mg/kg, i.p.) or allylisopropylacetamide (200 mg/kg, s.c.). AMTB also blocked the synthesis of rat hepatic porphyrins and inhibited the increase in the urinary excretion of δ-aminolevulinic acid and porphobilinogen following DDC (150 mg/kg, p.o.) administration. Preincubation of AMTB with liver mitochondria or a soluble fraction of liver decreased the activity of mitochondrial ALA synthetase and soluble ALA dehydrase, respectively.     

Central mechanisms of action involved in cocaine-induced tachycardia

The present study was designed to determine the central effects of cocaine on heart rate and blood pressure in Wistar Kyoto rats (WKY) and to evaluate mechanisms involved in the response. Cocaine (0.025-4 mg/kg) was administered to unanesthetized, unrestrained rats via a cannula placed into the lateral ventricle. Procaine (0.1 and 4 mg/kg) was also administered centrally. Cocaine did not significantly alter blood pressure at doses of 0.025, 0.1, or 0.5 mg/kg, icv. Only the highest dose, 4 mg/kg, icv produced a significant pressor response. Cocaine produced significant dose-dependent tachycardia, with the maximum increase in heart rate occurring within 5 min. Procaine (4 mg/kg, icv) produced tachycardia, but the effect was significantly less than that produced by cocaine (4 mg/kg, icv). Cocaine also produced tachycardia at a dose of 0.1 mg/kg, but procaine did not significantly alter heart rate at the same dose. Central phentolamine pretreatment (0.1 mg/kg, icv) significantly attenuated the increase in heart rate produced by cocaine. These results indicate that the centrally mediated tachycardia produced by cocaine is partly due to its local anesthetic activity and to indirect stimulation of alpha receptors.     

Phenytoin induced oxidative stress in pre- and postnatal rat development - effect of vitamin E on selective biochemical variables

A pre- and postnatal study was carried out to investigate the effect of high dose (500 mg/kg) of the natural antioxidant vitamin E (VIT E) on biochemical variables in the model of chronic intrauterine hypoxia. Chronic hypoxia was induced by administration of the anticonvulsant phenytoin (PHT) during pregnancy. Rats were orally treated with PHT (150 mg/kg) from day 7 to 18 of gestation and VIT E prior to PHT orally on the same days. The activity of the lysosomal enzyme N-acetyl-ss-D-glucosaminidase (NAGA) and the level of glutathione (GSH) were used as markers of tissue damage. In the prenatal study PHT-induced embryofoetal toxicity was associated with an increase in NAGA activity and decrease of GSH level in maternal serum and heart and with an increase in NAGA activity in the placenta. Administration of VIT E did not inhibit the above given changes. PHT increased the activity of NAGA and decreased the level of GSH in foetal organs (liver, lungs, brain). VIT E did not reverse these changes. In the postnatal study, we did not find any significant differences in NAGA activity in the organs of 1-day-old pups. An increase of liver GSH level was found in PHT and VIT E+PHT groups of pups and in the group VIT E+PHT in the lungs. In conclusion, supplementation with a high-dose of VIT E failed to protect maternal, foetal and new-born rat organs from PHT induced changes of selective biochemical variables.     

Effects of combined administration of captopril and DMSA on arsenite induced oxidative stress and blood and tissue arsenic concentration in rats

We compared the therapeutic efficacy of captopril and a thiol chelating agent, meso 2,3-dimercaptosuccinic acid (DMSA) either individually or in combination against arsenite induced oxidative stress and mobilization of metal in rats. Animals were exposed to 100 ppm arsenite as sodium arsenite in drinking water for six weeks followed by treatment with DMSA (50 mg/kg, orally), captopril (50 mg/kg, intraperitoneally) either alone or in combination, once daily for 5 consecutive days. Arsenite exposure led to a significant depletion of blood delta-aminolevulinic acid dehydratase (ALAD) activity, glutathione and platelet levels while significantly increased the level of reactive oxygen species (in RBCs). Hepatic reduced glutathione (GSH) level showed a significant decrease while, thiobarbituric acid reactive substances (TBARS) levels increased on arsenite exposure indicating arsenite induced hepatic oxidative stress. Kidney GSH, GSSG, catalase and TBARS remained unchanged on arsenite exposure. Treatment with DMSA was effective in increasing ALAD activity while, captopril was ineffective when given alone. Captopril when co-administered with DMSA also provided no additional beneficial effect on blood ALAD activity but significant brought altered platelet counts back to the normal value. In contrast, administration of captopril alone provided significant beneficial effects on hepatic oxidative stress, and in combination with DMSA provided a more pronounced recovery in the TBARS level compared to the individual effect of DMSA and captopril. Renal biochemical variables remained insensitive to arsenite and any of the treatments. Interestingly, combined administration of captopril with DMSA had a remarkable effect in depleting total arsenic concentration from blood and soft tissues. These results lead us to conclude that captopril administration during chelation treatment had some beneficial effects particularly on the protection of inhibited blood ALAD activity, and depletion of arsenic level. The study supports our earlier conclusion that a co-administration of an antioxidant is more beneficial than monotherapy with the chelating agents, in order to achieve optimal effects of chelation in arsenite toxicity.     

Zinc and N-acetylcysteine modify mercury distribution and promote increase in hepatic metallothionein levels

This study investigated the ability of zinc (Zn) and N-acetylcysteine (NAC) in preventing the biochemical alterations caused by mercury (Hg) and the retention of this metal in different organs. Adult female rats received ZnCl₂ (27 mg/kg) and/or NAC (5 mg/kg) or saline (0.9%) subcutaneously and after 24 h they received HgCl₂ (5 mg/kg) or saline (0.9%). Twenty-four hours after, they were sacrificed and analyses were performed. Hg inhibited hepatic, renal, and blood δ-aminolevulinic acid dehydratase (δ-ALA-D) activity, decreased renal total thiol levels, as well as increased serum creatinine and urea levels and aspartate aminotransferase activity. HgCl₂-exposed groups presented an important retention of Hg in all the tissues analyzed. All pre-treatments demonstrated tendency in preventing hepatic δ-ALA-D inhibition, whereas only ZnCl₂ showed this effect on blood enzyme. Moreover, the combination of these compounds completely prevented liver and blood Hg retention. The exposure to Zn and Hg increased hepatic metallothionein levels. These results show that Zn and NAC presented promising effects against the toxicity caused by HgCl₂.     

Possible role of an endogenous opioid in the antihypertensive action of propranolol in spontaneously hypertensive rats

The effect on systolic blood pressure and heart rate of the acute and chronic intraperitoneal (i.p.) administration of d- and dl-propranolol was investigated on unanesthetised spontaneously hypertensive rats. The effect of naloxone on the propranolol induced hypotension was also studied to test the hypothesis that the antihypertensive effect of propranolol involves the release of an endogenous opiate. On i.p. administration, 3 mg/kg d-propranolol was inactive; 3 and 30 mg/kg dl-propranolol decreased blood pressure and heart rate in a dose-dependent manner. When the rats were pretreated with 2 mg/kg naloxone i.p., the effect of propranolol on the blood pressure was nearly completely abolished, while that on the heart rate was only partially blocked. Chronic administration of dl-propranolol (30 mg/kg b.i.d.) to spontaneously hypertensive rats from the age of 6 weeks (prehypertensive phase) for 29 days prevented the development of hypertension while the rats treated with physiological saline for 29 days (control group) developed hypertension. Naloxone (2 mg/kg i.p.) administered on the 29th day to chronically treated rats induced a reversal of the propranolol action on systolic blood pressure and heart rate, i.e., blood pressure and heart rate increased. Naloxone had no such effect in the control group. We suggest that the release of an endogenous opioid contributes to the acute and chronic antihypertensive action of i.p. propranolol in spontaneously hypertensive rats and that the secretion of endogenous opioids participating in the control of cardiovascular functions is influenced by adrenergic mechanisms.     

Influence of L-lysine and zinc administration during exposure to lead or lead and ethanol in rats

Influence of lysine and zinc administration on the lead-sensitive biochemical parameters and the accumulation of lead during exposure to lead or lead and ethanol was investigated in rats. The lead exposure inhibited blood δ-aminolevulinic acid dehydratase (ALAD) activity, increased blood zinc protoporphyrin (ZPP), urinary δ-aminolevulinic acid (ALA), serum glutamic oxalacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), blood and tissue lead levels, and decreased blood and hepatic glutahione (GSH) contents. Some of these effects were enhanced on coexposure to ethanol. The simultaneous administration of lysine and zinc reduced tissue accumulation of lead and most of the lead-induced biochemical alterations irrespective of exposure to lead alone or lead and ethanol. The depletion of endogenous calcium and magnesium owing to lead or ethanol exposure was also prevented by co-administration of lysine and zinc.