Mercury Disposition in Suckling Rats: Comparative Assessment Following Parenteral Exposure to Thiomersal and Mercuric Chloride

Maja Blanuša,Tatjana Orct,Ankica Sekovanić,Martina Piasek,Maja Vihnanek Lazarus

doi:10.1155/2012/256965

Maja Blanuša, Tatjana Orct + Show 3 more

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https://doi.org/10.1155/2012/256965

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Abstract

Due to the facts that thiomersal-containing vaccine is still in use in many developing countries, and all forms of mercury have recognised neurotoxic, nephrotoxic, and other toxic effects, studies on disposition of ethylmercury and other mercury forms are still justified, especially at young age. Our investigation aimed at comparing mercury distribution and rate of excretion in the early period of life following exposure to either thiomersal (TM) or mercuric chloride (HgCl2) in suckling rats. Three experimental groups were studied: control, TM, and HgCl2, with 12 to18 pups in each. Both forms of mercury were administered subcutaneously in equimolar quantities (0.81 μmol/kg b.w.) three times during the suckling period (on the days of birth 7, 9, and 11) to mimic the vaccination regimen in infants. After the last administration of TM or HgCl2, total mercury retention and excretion was assessed during following six days. In TM-exposed group mercury retention was higher in the brain, enteral excretion was similar, and urinary excretion was much lower compared to HgCl2-exposed sucklings. More research is still needed to elucidate all aspects of toxicokinetics and most harmful neurotoxic potential of various forms of mercury, especially in the earliest period of life.

Highlights

Mercury is a pervasive environmental contaminant with proven toxic properties in mammals
Total mercury fraction in all analysed tissues of the control pups (N = 12; 2 pups in each litter) was more than 1000 times lower than values found in the exposed groups
Results show that mercury levels decreased in blood and urine in a time-dependent manner while mercury mass fractions in all selected organs remained relatively constant during six days following the parenteral exposure

Summary

Introduction

Mercury is a pervasive environmental contaminant with proven toxic properties in mammals. Major risks recognized due to mercury exposure are dietary methylmercury exposure from fish and seafood, elemental mercury vapour from amalgam in tooth “silver fillings,” and thiomersal-contained ethylmercury in vaccines [1,2,3]. Ethylmercury is acting as a preservative against bacterial and fungal contamination of the vaccines that are repeatedly given to infants (Diphtheria-Tetanus-acellularPertussis vaccine, 3 to 7 times) up to 6 months of age. A potential threat of neurodevelopmental toxic effect of mercury lies in the fact that the exposure occurs in the most vulnerable period of life, when the brain is developing and growing [8]. Organic forms of mercury are more absorbed when ingested and are less readily eliminated from the body than its inorganic forms [1]

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