MeHg-cysteine complexa involved in transport of MeHg into cells


Half-life in blood, 50 d; 50% of dose found in liver; 10% in head.

Half-life in blood, 45 d (slow phase); half-life appears to increase with increasing dose

Half-life in blood, 19.7-65.6 d; 1st phase, 24 d, 2nd phase, 15-30 d

Readily crosses blood-brain and placental barriers

Readily crosses blood-brain and placental barriers

Does not readily penetrate blood-brain or placental barriers


In neonate, mercuric Hg not concentrated in kidneys; therefore, more widely distributed to other tissues


In fetus and neonate, blood-brain barrier incompletely formed, so mercuric Hg brain concentrations higher than those in adults



MeHg slowly demethylated to mercuric Hg (Hg2+)

Hg0 in tissue and blood oxidized to Hg2+ by catalase and hydrogen peroxide (H2O2); H2O2 production the rate-limiting step

Hg0 vapor exhaled by rodents following oral administration of mercuric Hg

Tissue macrophages, intestinal flora, and fetal liver are sites of tissue demethylation


Mercuric Hg not methylated in body tissues but GI microorganisms can form MeHg

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