Maria Ester Pereira

Effect of treatment with mercury chloride and lead acetate during the second stage of rapid postnatal brain growth on δ-aminolevulinic acid dehydratase (ALA-D) activity in brain, liver, kidney and blood of suckling rats

The sensitivity of developing rodents to toxic metals differs considerably from that of adults. In the present study, we investigated the in vivo and in vitro effects of inorganic mercury and lead on delta-aminolevulinic acid dehydratase (ALA-D) from brain, liver, kidney and blood of young rats. Eight day-old rats were injected with one or five doses of lead acetate (0, 3.5, or 7.0 mg/kg) or HgCl2 (0, 2.5, or 5.0 mg/kg). In vitro, the IC50 for mercury inhibition of cerebral, renal and hepatic ALA-D was in the 124 to 160 microM range, while values for lead acetate was in the 7 to 12 microM range. The IC50 of blood enzyme for lead (0.8 microM) and mercury (6.5 microM) was significantly lower than that observed for the other tissues. A single dose of lead did not affect the enzyme activity, but a single dose of HgCl2 (5 mg/kg) caused a significant inhibition of ALA-D from kidney (40%, P < 0.01) and liver (25%, P < 0.05). Five doses of lead acetate (3.5 or 7 mg/kg) caused an inhibition of about 25 and 40%, respectively (P < 0.01), of hepatic ALA-D, and an increase of 1.4-fold (P < 0.05) and 2.6-fold (P < 0.01) of blood enzyme, respectively. Treatment with five doses of HgCl2 (5 mg/kg) caused an inhibition of about 25, 60, 50, and 80% of ALA-D from brain, blood, liver and kidney, respectively (all P < 0.05). Five doses of 2.5 mg/kg HgCl2 caused an inhibition of ALA-D from liver (40%, P < 0.01) and kidney (45%, P < 0.01). These results demonstrate that ALA-D from young rat tissues show different sensitivities to mercury and lead. The enzyme was more affected by mercury than by lead in vivo, while in vitro lead was more potent that mercury as an ALA-D inhibitor.

Antinociceptive activity of Mirabilis jalapa in mice

ETHNOPHARMACOLOGICAL RELEVANCE The infusion or decoction of Mirabilis jalapa leaves is used in traditional medicine in Brazil to treat inflammatory and painful diseases. AIM OF THE STUDY The present study examined the antinociceptive effect of Mirabilis jalapa extracts from leaves and stems in models of pain in mice. MATERIALS, METHODS AND RESULTS The crude hydroethanolic extract from leaves (CrdL) was more potent than the crude extract from stems (CrdS) to inhibit abdominal constrictions induced by acetic acid, with ID(50) values of 5.5 (2.3-13.1) and 18.0 (11.3-28.5) mg/kg, respectively. Among the fractions tested, the Eta fraction from leaves (Eta) was more effective (maximal inhibition of 83+/-8%) and potent (ID(50) of 1.1 (0.6-2.1) mg/kg) to induce antinociception. Eta and CrdL also possessed an antinociceptive effect in the tail-flick test. Pre-treatment with naloxone did not modify the antinociceptive effect of Eta, but co-administration with atropine completely prevented it. This suggests that the antinociceptive effect might depend on the cholinergic system. Instead, Eta was not able to alter the acetylcholinesterase activity in blood or spinal cord. Concerning side effects, Eta did not alter locomotor activity, body temperature, gastrointestinal transit and did not produce gastric lesions. CONCLUSION Our results demonstrate that Mirabilis jalapa presents antinociceptive activity in mice, which supports its folkloric use as an analgesic.

Diphenyl diselenide reverses gastric lesions in rats: Involvement of oxidative stress

The aim of the present study was to evaluate if diphenyl diselenide administered by oral route was effective in restoring gastric lesions induced by ethanol. The possible involvement of oxidative stress in diphenyl diselenide antiulcer effect was also evaluated. Different doses of diphenyl diselenide (dissolved in soya bean oil, 1mL/kg) were administered orally 1h before (pre-treatment study) or 1h after ethanol (70%, v/v, 2mL/kg, post-treatment study). Ulcer lesions were quantified 1h after ethanol administration (pre-treatment protocol) or 1h after diphenyl diselenide study (post-treatment protocol). Diphenyl diselenide (0.1-10mg/kg or 0.32-32micromol/kg), when administered previously or posteriorly prevented and reversed respectively, the development of gastric lesions induced by ethanol in rats. A number of markers of oxidative stress were examined in rat stomach including thiobarbituric acid reactive species (TBARS), catalase (CAT), superoxide dismutase (SOD), non-protein thiol groups (NPSH) and ascorbic acid. In addition to attenuating the gastric lesions, low doses of diphenyl diselenide prevented (pre-treatment) or reversed (post-treatment) the ethanol-induced changes in TBARS, SOD activity and ascorbic acid content. In conclusion, the present data reveal that diphenyl diselenide, administered by oral route, possesses an antiulcer effect by modulating antioxidant mechanisms.

Effect of mercuric chloride and lead acetate treatment during the second stage of rapid post-natal brain growth on the behavioral response to chlorpromazine and on δ-ALA-D activity in weaning rats

During the early post-natal period the brain is extremely sensitive to external agents. In the present study, we examined the effects of the treatment with lead acetate (3.5 or 7.0 mg/kg) and mercuric chloride (2.5 or 5.0 mg/kg) during the early post-natal period (day 8-12) on the behavioral response to chlorpromazine (CPZ) of 22-day-old rats. The effects of these metals on the sulfhydryl-containing enzyme delta-aminolevulinate dehydratase (delta-ALA-D) were also investigated. Mercuric chloride (2.5 mg/kg) did not affect brain enzyme activity, but caused a significant stimulation of renal delta-ALA-D of 24-day-old rats (27%), while animals treated with 5 mg/kg HgCl(2) showed a small but significant inhibition of cerebral (10%) and renal delta-ALA-D activity (15%). Lead acetate (3.5 or 7 mg/kg) treatment did not affect renal or cerebral delta-ALA-D. Mercuric chloride treatment (5 mg/kg) changed the pattern of open-field activity and the CPZ-induced catalepsy. However, since the undernutrition that accompanied the metal treatment also caused changes in CPZ-induced catalepsy, the effect of mercury on catalepsy could not be clearly established. Lead acetate treatment (7 mg/kg) changed the pattern of open-field motor activity and abolished the decrease in activity observed in control rats. The cataleptic response of animals to CPZ was also affected by lead acetate treatment (7 mg/kg). The increase in activity is compatible with the hyperactivity described in animals exposed to lead for long periods. Thus, the present study suggests that a short exposure to lead or mercury during suckling (second stage of rapid post-natal brain growth) caused permanent changes in locomotor activity that can be interpreted as hyperactivity. Additionally, the behavioral response to CPZ was affected by metal treatment indicating an alteration in the dopaminergic system.

Delayed biochemical changes induced by mercury intoxication are prevented by zinc pre-exposure.

This work evaluated the delayed effects of mercury and the effectiveness of zinc in preventing such effects. Pups were pre-treated with 1 daily dose of ZnCl(2) (27 mg/kg/day, by subcutaneous injections) from 3rd to 7th postnatal day and received 1 daily dose of 5 mg/kg of HgCl(2), for 5 subsequent days (8-12 days old). Animals were euthanized 21 days after the end of Hg-exposure. Porphobilinogen-synthase activity as well as zinc and mercury contents was determined in the liver and kidneys. Alanine aminotransferase, aspartate aminotransferase and lactic dehydrogenase activities as well as urea, creatinine and glucose levels were analyzed in plasma or serum. Some animals were considered more sensitive to mercury, since they did not recover the body weight gain and presented an increase of renal and hepatic mercury content, urea and creatinine levels; a decrease in renal porphobilinogen-synthase and alanine aminotransferase activities, as well as a decrease in the liver and an increase in kidney weights. Some animals were considered less sensitive to mercury because they recovered the body weight and presented no biochemical alterations in spite of mercury in the tissues. Zinc prevents partially or totally the alterations caused by mercury even those that persisted for a long time after the end of exposure. These findings suggest that there is difference among the animals regarding the sensitivity to mercury.

ZnCl2 exposure protects against behavioral and acetylcholinesterase changes induced by HgCl2.

This study examined the effects of inorganic mercury exposure on behavioral and biochemical parameters and investigated the possible preventive effects of zinc on the alterations induced by mercury. Pups were exposed from 3rd to 7th postnatal day to ZnCl2 (27 mg/kg/day, s.c.) and subsequently to HgCl2 (5 doses of 5 mg/kg/day, s.c.). Each litter contained two rats for each treatment. The rats were submitted to behavioral task and litters were killed at 13 or 33 days old for acetylcholinesterase activity assays and for the determination of metal levels. Based on the results obtained from 13‐day‐old rats, they were divided in two groups of litters that were defined at the end of the experimental period (33 days) as less sensitive rats to mercury and more sensitive rats to mercury in accordance with the recovery of body weight until day 33. The mercury exposure caused accumulation of this metal in cerebrum and cerebellum in all mercury treated rats, and inhibited the cerebellum acetylcholinesterase activity from 13‐day‐old rats. Besides, the mercury‐animals of the most sensitive litters to mercury presented impairment in motor function and muscular strength verified in the beaker test, as well as a reduction of the locomotor and exploratory activities in the open field task. Zinc partially prevented all the alterations induced by mercury exposure and reduced the mercury level accumulated in cerebrum and cerebellum. This study confirms the preventive effect of zinc on behavioral alterations induced by mercury in young rats and demonstrates that the mercury behavioral effects are present even for a long time after the end of the exposure.

Behavioral alterations induced by HgCl2 depend on the postnatal period of exposure.

This paper shows the toxicity of mercury (HgCl2 5 mg/kg/day for 5 days, sc) applied at specific stages of development (1–5, 8–12 or 17–21 days old, 1st, 2nd and 3rd phases, respectively) on the performance of rats in three behavioral tasks and on cerebral mercury levels. The mercury exposure at the 1st and 2nd phases affected the performances of rats in the rim escape. Spontaneous alternation behavior was not altered by mercury exposure. In the open field task, habituation was absent when the rats were treated at the 1st phase, and the crossing response number was lower in rats exposed to mercury at the last period. In general, the brain accumulated large quantities of mercury. In short, the first days of postnatal life (1st phase) appeared to be more sensitive to mercury exposure than the other phases studied, since they presented behavioral deficits even at a time period somewhat after the exposure.

Butane-2,3-dionethiosemicarbazone: an oxime with antioxidant properties.

Oximes are compounds generally used to reverse the acetylcholinesterase (AChE) inhibition caused by organophosphates (OPs). The aim of this study was to examine the capacity of the butane-2,3-dionethiosemicarbazone oxime to scavenge different forms of reactive species (RS) in vitro, as well as counteract their formation. The potential antioxidant and toxic activity of the oxime was assayed both in vitro and ex vivo. The obtained results indicate a significant hydrogen peroxide (H2O2), nitric oxide (NO) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity at 0.275, 0.5 and 5microM of oxime, respectively (p< or =0.05). The oxime exhibited a powerful inhibitory effect on dihydroxybenzoate formation (25microM) (p< or =0.05) and also decreased deoxyribose degradation induced by Fe2+ and via Fenton reaction (0.44 and 0.66mM, respectively) (p< or =0.05). The oxime showed a significant inhibitory effect on sigma-phenantroline reaction with Fe2+ (0.4mM) suggesting a possible interaction between the oxime and iron. A significant decrease in the basal and pro-oxidant-induced lipid peroxidation in brain, liver, and kidney of mice was observed both in vitro and ex vivo (p< or =0.05). In addition, in our ex vivo experiments the oxime did not depict any significant changes in thiol levels of liver, kidney and brain as well as did not modify the delta-aminolevulinate dehydratase (delta-ALA-D) activity in these tissues. Taken together our results indicate an in vitro and ex vivo antioxidant activity of the oxime possibly due to its scavenging activity toward different RS and a significant iron interaction.

Antioxidant effect of zinc chloride against ethanol-induced gastrointestinal lesions in rats

The aim of the present study was to evaluate the possible effects of zinc chloride against the gastrointestinal lesions caused by oral administration of ethanol in rats. Rats were divided into five groups, namely, saline, ethanol, zn, zn+ethanol and ethanol+zn. Ethanol 70% (2 mL/kg) was administered by gavage in 36 h fasted rats. Zinc chloride (27 mg/kg, ~13 mg/kg of zinc) was given by gavage 1h before or 1h after the administration of ethanol. Oral administration of ethanol consistently induced damage in the rat glandular stomach and intestine. Zinc did not demonstrate effect per se and significantly reduced gastrointestinal lesions when administered either before or after lesion induction. Ethanol induced enhancement of thiobarbituric acid reactive substance and reactive species levels, diminished the ascorbic acid and total protein SH content as well as superoxide dismutase and catalase activity in stomach and intestine of rats. Zinc treatment prevented and reversed these alterations induced by ethanol. Stomach and intestine of rats treated with zinc presented higher zinc content than the tissues of rats treated only with ethanol. Non-protein SH content was not altered by any treatment. Results suggested that the gastrointestinal protective effect of zinc in this experimental model could be due to its antioxidant effect.

Changes in levels of essential elements in suckling rats exposed to zinc and mercury.

The effect of mercury and its interaction with zinc on the content of essential metals in tissues from neonate rats was investigated. Three-day-old Wistar rats were treated with saline or 27 mg kg(-1)d(-1) ZnCl2 (s.c.) for five consecutive days. From the 8th to the 12th day of life, the rats received one daily dose of saline or 5.0 mg kg(-1) HgCl2 (s.c). Twenty-four hours after the last injection liver, kidneys and blood were collected for metal quantification. The HgCl(2) exposure induced alterations on metal levels, such as increase of Fe, Hg and Zn in liver, decrease of Fe and Mg and increase of Cu and Hg contents in kidneys. The Hg exposure also increased Hg levels in the blood. The treatment with ZnCl2, administered previously to HgCl2, partially prevented the increase of Fe in the liver, and not only prevented the decrease of renal Mg but also increased it to levels higher than those found in control group. The Zn-Hg rats also presented higher renal Cu levels, and showed partially lower blood and hepatic Hg levels and higher renal Hg levels. The pre-administration of Zn caused no severe alterations in levels of essential metals (Cu, Fe, Mg and Mn). In short, Zn appears to be an alternative treatment of Hg poisoning in young animals in comparison to chelating drugs since these have low metal selectivity.