Elimination of Toxicants

As organisms evolved in complexity, several consequences of increased complexity compromised the efficiency of the passive diffusion of toxic chemicals  

Their surface area to body mass decreased. 

Their bodies compartmentalized (i.e., cells, tissues, organs). 

With increased size of an organism, a toxic chemical has greater distance to traverse before reaching a membrane across which it can diffuse to the external environment. Thus overall retention of the chemical will increase as will propensity for the chemical to elicit toxicity. 

Surface Area to Body Mass Ratio. Increased size of an organism is associated with a decrease in the surface area to body mass ratio. Accordingly, the availability of surface membranes across which a chemical can passively diffuse to the external environment decreases and propensity for retention of the chemical increases. 

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The kidney is an important organ for the excretion of toxic materials and their metaboHtes, and measurement of these substances in urine may provide a convenient basis for monitoring the exposure of an individual to the parent compound in his or her immediate environment. The Hver has as one of its functions the metaboHsm of foreign compounds some pathways result in detoxification and others in metaboHc activation. Also, the Hver may serve as a route of elimination of toxic materials by excretion in bile. In addition to the Hver (bile) and kidney (urine) as routes of excretion, the lung may act as a route of elimination for volatile compounds. The excretion of materials in sweat, hair, and nails is usually insignificant. 

Cellular defense mechanisms against toxins (A multistep mechanism for elimination of toxic metabolites and xenobiotics. It involves various transport, oxidation, and conjugation steps.) are usually divided into several steps as it is visualized on Fig. 3. Organic anion transporting proteins (OATPs) are responsible for the cellular uptake of endogenous compounds and... 

Toxicokinetic—The study of the absorption, distribution and elimination of toxic compounds in the living organism. 

Guerrier, P., J.P. Weber, R. Cote, M. Paul, and M. Rhainds. 1995. The accelerated reduction and elimination of toxics in Canada the case of mercury-containing medical instruments in Quebec hospital centres. 

As it follows from Table 21.8, Enterosgel has low capacity towards medicinal preparations studied as opposed to activated carbon. It does not mean that carbon sorbents should not be used for elimination of toxic effects of prolonged drug therapy - for this purpose one could separate dmg administration from sorbent administration by 1-2 hours, and introduce meal consumption between them, however, in such cases Enterosgel is surely more suitable. 

Matthews HB. Excretion and elimination of toxicants and their metabolites. In Hodgson E, Levi PE, eds. Introduction to Biochemical Toxicology. 2nd ed. New York Elsevier-North Holland, 1994. 

Barriers to the Environment. Through evolution, increased complexity of organisms led to increased exploitation of various environments. In order to survive in these environments, organisms developed barriers such as skin and scales that protect from harsh conditions on the outside and minimize loss of vital constituents such as water on the inside. Likewise these barriers impede the elimination of toxic constituents by the organisms, requiring the development of specialized membranes and organs through which toxic materials can be eliminated. 

A consequence of this hindrance to elimination of toxic materials by complex organisms was the development of specialized routes of elimination. These routes generally evolved in concert (i.e., co-evolved) with biotransformation processes that render chemicals amenable to these modes of elimination (see Chapters 7-9). 

Any actions taken as a result of the preliminary assessment phase can result in a reduction or elimination of toxicity, negating the need for further investigation. In addition, at this early stage of the TRE, management attention will often lead to subtle operational changes, which in turn, may result in a reduction or elimination of acute lethality without a clearly identified cause (Ausley et al., 1998). 

Figure 6.2 Major sites of exposure, metabolism, and storage, and routes of distribution and elimination of toxic substances in the body. 

List and discuss the major routes and sites of exposure, distribution, and elimination of toxicants in the body. 

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