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.
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.
Resumo -O objetivo deste trabalho foi verificar a influência da idade, sexo, manejo e estado gestacional sobre a atividade sérica das enzimas: aspartato aminotransferase (AST), creatina quinase (CK) e gama-glutamiltransferase (GGT) em cavalos da raça Crioula. Foram utilizados 142 eqüinos, divididos em seis grupos: potros até um ano de idade; cavalos adultos em regime de atividade livre; cavalos adultos em treinamento; machos adultos; fêmeas não gestantes; fêmeas gestantes. O valor da CK foi mais elevado em animais adultos do que em potros, o mesmo tendo ocorrido em animais em atividade livre, comparados a animais em treinamento. Fêmeas não gestantes apresentaram valores das enzimas CK e GGT maiores que os machos; o valor da CK em fêmeas gestantes foi mais elevado do que em fêmeas não gestantes. A idade, o sexo, o manejo e o estado gestacional influenciam a atividade sérica da CK, e o sexo influencia a atividade sérica da GGT.Termos para indexação: bioquímica sérica, enzimas musculares, doenças hepáticas, miopatia. AST, CK and GGT enzymes serum activities in Crioulo horsesAbstract -The objective of this work was to evaluate the influence of age, sex, management and pregnancy status on aspartate aminotransferase (AST), creatine kinase (CK) and gamma-glutamyltransferase (GGT) enzymes serum activities of Crioulo horses. One hundred and forty-two horses, divided into six group were analyzed: yearlings; free activity of adult horses; training adult horses; male adult horses; nonpregnant and pregnant females. The CK enzyme activity value was higher in adult horses than in yearlings, and the same result was found when comparing free activity and training horses. Nonpregnant females had higher values for CK and GGT comparing to male horses, and CK values were higher in pregnant comparing to nonpregnant females. Age, sex, management and pregnancy status influence on CK serum activity, and sex influences on GGT serum activity.Index terms: serum biochemistry, muscular enzyme, hepatic disease, myopathy. IntroduçãoOs sinais clínicos presentes em distintas alterações musculares são semelhantes e bastante inespecíficos; por isso, quando isolados, eles têm limitado valor diagnóstico, o que requer, freqüentemente, o uso de exames laboratoriais complementares. Entre as enzimas, cujas concentrações séricas devem ser determinadas quando de disfunções musculares, estão aspartato aminotransferase (AST) e a creatina quinase (CK) (Da Cás et al., 2000). Além disso, a patogenia de doenças hepáticas nos animais domésticos é muito complexa, por isso, o diagnóstico dessas enfermidades também envolve testes bioquímicos, entre os quais o uso da enzima gama-glutamiltransferase (GGT) como marcador sérico primário, para doenças do sistema hepatobiliar associadas com colestase (Tennant, 1997).A aspartato aminotransferase (AST) é uma enzima citoplasmática e mitocondrial, presente em vários tecidos como fígado, músculos esquelético e cardíaco (Tennant, 1997;Frape, 1998). Tennant (1997) salienta que em todas as espécies domésticas a atividade da AST ...
This study evaluated the effects of HgCl2 on renal parameters in nonlactating and lactating rats and their pups, as well as the preventive role of ZnCl2 . Rats received 27 mg kg(-1) ZnCl2 for five consecutive days and 5 mg kg(-1) HgCl2 for five subsequent days (s.c.). A decrease in δ-aminolevulinic acid dehydratase (δ-ALA-D) activity in the blood and an increase in urine protein content in renal weight as well as in blood and urine Hg levels were observed in lactating and nonlactating rats from Sal-Hg and Zn-Hg groups. ZnCl2 prevented partially the δ-ALA-D inhibition and the proteinuria in nonlactating rats. Renal Hg levels were increased in all HgCl2 groups, and the ZnCl2 exposure potentiated this effect in lactating rats. Nonlactating rats exposed to HgCl2 exhibited an increase in plasma urea and creatinine levels, δ-ALA-D activity inhibition and histopathological alterations (necrosis, atrophic tubules and collagen deposition) in the kidneys. ZnCl2 exposure prevented the biochemical alterations. Hg-exposed pups showed lower body and renal weight and an increase in the renal Hg levels. In conclusion, mercury-induced nephrotoxicity differs considerably between lactating and nonlactating rats. Moreover, prior exposure with ZnCl2 may provide protection to individuals who get exposed to mercury occupationally or accidentally.
This work investigated the in vivo and in vitro effects of HgCl2 and ZnCl2 on metabolic enzymes from tissues of young rats to verify whether the physiological and biochemical alterations induced by mercury and prevented by zinc are related to hepatic and renal glucose metabolism. Wistar rats received (subcutaneous) saline or ZnCl2 (27 mg/kg/day) from 3 to 7 days old and saline or HgCl2 (5.0 mg/kg/day) from 8 to 12 days old. Mercury exposure increased the hepatic alanine aminotransferase (∼6-fold) and glucose 6-phosphatase (75%) activity; zinc pre-exposure prevented totally and partially these mercury alterations respectively. In vitro, HgCl2 inhibited the serum (22%, 10 μM) and liver (54%, 100 μM) alanine aminotransferase, serum (53%) and liver (64%) lactate dehydrogenase (10 μM), and liver (53%) and kidney (41%) glucose 6-phosphatase (100 μM) from 10- to 13-day-old rats. The results show that mercury induces distinct alterations in these enzymes when tested in vivo or in vitro as well as when different sources were used. The increase of both hepatic alanine aminotransferase and glucose 6-phosphatase activity suggests that the mercury-exposed rats have increased gluconeogenic activity in the liver. Zinc prevents the in vivo effects on metabolic changes induced by mercury.
This study investigated if lactating and nonlactating rats presented differences in relation to hepatic sensitivity to HgCl2 and the potential preventive role of ZnCl2. Lactating (days 3-12 of lactation) and nonlactating rats received 27 mg/kg ZnCl2 for five consecutive days and 5 mg/kg HgCl2 for five subsequent days. Lactating and nonlactating rats exposed to HgCl2 presented a decrease in food intake, a decrease in plasma alanine aminotransferase (ALT), and an increase in hepatic Hg levels when compared to the control group. Only lactating rats exposed to HgCl2 presented an increase in hepatic δ-aminolevulinic acid dehydratase activity. On the other hand, only nonlactating rats exposed to HgCl2 presented an increase in plasma aspartate aminotransferase (AST). ZnCl2 pre-exposure partially protected the increase in plasma AST activity presented by nonlactating rats and potentiated the liver Hg accumulation in lactating rats. Pups from the Sal-Hg and Zn-Hg groups showed a decrease in absolute liver weight and an increase in liver Hg levels. Summarizing, this study demonstrated that lactating rats presented distinct biochemical responses compared to nonlactating rats exposed to HgCl2 when hepatic parameters were evaluated.
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