Biologic systems mercury toxicity

Mercury is essentially nontoxic in its elemental form (Hg ). In the absence of any chemical or biological system that chemically alters Hg , it can be consumed orally without any significant side effects. However, once Hg is chemically modified to the ionized, inorganic species, Hg T it becomes toxic. Further bioconversion to an alkyl Hg, such as methyl Hg (CHaHg ), yields a very toxic species of Hg that is highly selective for lipid-rich tissue, such as the neuron. The relative order of toxicity is as follows ... 

The development of probes for the toxic heavy metals mercury, cadmium and lead in biological systems is of special interest In this context, selectivity is particularly important since alkali and alkaline earth metals (e.g. Na", K", ... 

The biological eflect of an element is not only dependent on the total concentration, but also highly related to its chemical forms present in biological systems, e.g. the oxidation state, the nature of the ligands or even the molecular structure. Dramatic examples are chromium, tin and mercury, to name just a few. Cr(VI) ions are considered far more toxic than Cr(III). Although the inorganic forms of tin and mercury are less toxic or even do not show toxic... 

Of the 110 or so elements there are only about 22 which occur naturally in biological systems. The use of therapeutic agents introduces about another half dozen. In earlier centuries before the advent of selective antimicrobial agents the use of the toxic elements mercury and antimony was very popular to treat the then, more or less, incurable diseases of syphilis and malaria. If a cure was effective it was often a pretty close tun thing with its opposite. 

The increase in toxicity can be explained by the increasing affinity of these elements for amino, imino, and sulfhydtyl groups, which form the active centers of a number of enzymes. The metals of the sixth Period and their compounds are potentially the most toxic elements of the Periodic System. The generally poor water solubility of their salts, however, often masks their inherent high degree of toxicity. This toxicity becomes apparent in those lead, mercury, and thallium salts that are relatively soluble. The metallic ions of the fourth Period form mostly covalent bonds and complexes with biological ligands, and some form hydroxy acids in which the metal is part of the anion. 

Gold is not an essential element for living systems. Indeed, administration of gold dmgs to patients resulted in effects more similar to that of toxic elements, such as mercury, than to that of biologically utilized transition elements such as copper and iron. Gold distributes... 

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