ZnCl₂ exposure protects against behavioral and acetylcholinesterase changes induced by HgCl₂

Abstract

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.

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

“…Inorganic mercury also affects liver, blood, intestine, thyroid and testicles [3,4]. In fact, recent studies have demonstrated that animals exposed to mercury chloride (HgCl 2 ) (5 mg/kg) present renal [5][6][7][8], hepatic [9][10][11][12], testicular [13], behavioral [14,15] and cardiovascular [16] alterations.…”

Effectiveness of copper chloride in protecting against alterations induced by mercury chloride in newborn rats

“…The dose of HgCl 2 was selected according to previous studies performed with suckling rats, which demonstrated several biochemical and physiological damages induced by this dose [4][5][6]11,15,17]. From 8 to 12 days old they received one daily dose of saline or HgCl 2 5 mg/kg/day (3.7 mg/kg/day of Hg).…”

“…Its toxicity depends on the chemical form in which the exposure occurs [1,2]. However, several studies have related other toxic effects induced by the inorganic form of mercury, such as (1) changes in body and organ weight [5,6], (2) hematological and immunological alterations [7], (3) inhibition of porphobilinogen synthase (PBG-synthase) activity of different tissues in vivo [5,6,[8][9][10] and in vitro [8,9], (4) inhibition of cerebellum acetylcholinesterase [11], and (5) serum alanineaminotransferase (ALT) activities, and (6) increase of serum creatinine and urea levels [4,5]. However, several studies have related other toxic effects induced by the inorganic form of mercury, such as (1) changes in body and organ weight [5,6], (2) hematological and immunological alterations [7], (3) inhibition of porphobilinogen synthase (PBG-synthase) activity of different tissues in vivo [5,6,[8][9][10] and in vitro [8,9], (4) inhibition of cerebellum acetylcholinesterase [11], and (5) serum alanineaminotransferase (ALT) activities, and (6) increase of serum creatinine and urea levels [4,5].…”

“…However, several studies have related other toxic effects induced by the inorganic form of mercury, such as (1) changes in body and organ weight [5,6], (2) hematological and immunological alterations [7], (3) inhibition of porphobilinogen synthase (PBG-synthase) activity of different tissues in vivo [5,6,[8][9][10] and in vitro [8,9], (4) inhibition of cerebellum acetylcholinesterase [11], and (5) serum alanineaminotransferase (ALT) activities, and (6) increase of serum creatinine and urea levels [4,5]. This justifies why developing animals are particularly sensitive to extern insults, such as those caused by heavy metals [4][5][6][8][9][10][11][13][14][15][16][17][18]. This justifies why developing animals are particularly sensitive to extern insults, such as those caused by heavy metals [4][5][6][8][9][10][11][13][14][15][16][17][18].…”

Preventive Effect of CuCl2on Behavioral Alterations and Mercury Accumulation in Central Nervous System Induced by HgCl2in Newborn Rats

“…Inorganic mercury (HgCl 2 ) is primarily nephrotoxic ; however, its effect on CNS during early periods of development is well documented. In fact, we recently demonstrated that HgCl 2 induces behavioral impairment and accumulation of this metal in the cerebrum and cerebellum .…”