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.

Sensitivity of young rats to nicotine exposure: Physiological and biochemical parameters.

This work has investigated the effects of prolonged exposure of young rats to nicotine on some physiological and biochemical parameters. Wistar male rats (30 days old) were treated (s.c.) with saline or nicotine 5mg/kg/day for 28 or 56 days. They received five injections (1mg/kg) per day (8, 10, 12:00 a.m., 2 and 4:00 p.m.) on the dark period of the cycle. Nicotine exposure for 56 days reduced body and liver weights. Moreover, nicotine exposure for 28 or 56 days decreased the hepatic glycogen but not blood glucose levels. The activities of blood and hepatic PBG-synthase, and blood and cerebral acetylcholinesterase were not affected by in vivo exposure. However, these activities were inhibited by nicotine in vitro. Results show that although high levels of plasma cotinine were found in both intervals of exposures, the parameters here analyzed were not affected by prolonged nicotine exposure except the storage of glucose, and body and liver weights.

Avaliação da solução euro-collins como um meio de conservação do enxerto no transplante renal em cães

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