An introduction to the excretion and elimination of toxicants and their metabolites

The molecular weight of a compound will determine if the compound will be excreted in the urine or feces. This dealkylation occurs after the OP inhibits an esterase, specifically neuropathy target esterase NTE; also known as neurotoxic esterase.

The rapid absorbance of these compounds does not mean that they will not be readily excreted. However, organochlorine compounds are reabsorbed to some degree in the enterohepatic circulation and this recycling phenomenon accounts for the persistence within the human body [ 52 ].

Substitution at other sites on the ortho-substituted ring decreases the neurotoxicity. The biliary route is an important mechanism for fecal excretion of xenobiotics and is even more important for the excretion of their metabolites.

Many foreign compounds that enter the body are lipophilic, because of which they can easily penetrate lipid membranes and be transported by lipoproteins in body fluids. A metabolic reaction may dictate the rate of elimination. The resulting metabolites are then more readily excreted.

Pesticide Toxicology

In a similar nation-wide epidemiological study in Canada, Health Canada also reported on an assortment of stockpiled chemical toxicants within the general population [ 47 ]. Urine pH, which varies from 4. Those substances that are ionized remain in the urine and leave the body.

In the cation transport system, cations or organic bases eg, pramipexole, dofetilide are secreted by the renal tubules; this process can be inhibited by cimetidine, trimethoprim, prochlorperazine, megestrol, or ketoconazole.

As a result of such persistence and the lipophilic nature of OCPs, these chemical agents tend to store and bioaccumulate in adipose tissues. Secretions include organic bases, which occur in the pars recta of the proximal tubule. The highest concentration of a toxin within an animal is not necessarily found in the organ or tissue on which it exerts its maximal effect the target organ.

Toxic effects may be local, but the toxicant must be dissolved and absorbed to some extent to affect the cell.

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Increasing the lipid content of the intestinal tract can enhance intestinal excretion of some lipophilic substances. Both passive and active modes of transport are used.

Human Elimination of Organochlorine Pesticides: Blood, Urine, and Sweat Study

An issue of particular concern is fetal and early life exposure to xenobiotics at critical times of development as a result of maternal exposure and bioaccumulation [ 48 ]. The role of transporters in cellular elimination is considered, and, finally, the use of excreted pesticides and their metabolites as biomarkers of exposure is summarized.

Asecond method used is the alveolobronchilar transport mechanism. The bile will then be reabsorbed by a process known as enterohepatic circulation. Therefore, the essence of such reactions is to introduce or expose a functional group that decreases the lipid solubility of the compound.

Un-ionized forms of drugs and their metabolites tend to be reabsorbed readily from tubular fluids. Normally, the anion secretory system eliminates metabolites conjugated with glycine, sulfate, or glucuronic acid. The biliary system contributes to excretion to the degree that drug is not reabsorbed from the GI tract.

Animals possess enzymes that can metabolize drugs, pesticides, secondary plant metabolites, and synthetic compounds as defense mechanisms, which are likely because of evolution in response to selective pressures for protection against many naturally occurring toxic products.

Exhaled Air The lungs represent an important route of excretion for xenobiotics and metabolites that exist in a gaseous phase in the blood. This results from the large amount of blood flow through the glomerulus, the relatively large pores 40 angstrom, an angstom is one one-hundred millionth of a centimeter in the glomerular capillaries, and the hydrostatic pressure of the blood.

Each kidney contains about one million nephrons. This is referred to as lethal synthesis. This means that they will be easily ablorbed and dispursed among the tissue.

• Biotransformation may result in formation of less toxic or more toxic metabolites • Rapid elimination will result in lower concentration and hence its toxicity in target tissues.

TOXICODYNAMICS. Essay Excretion and Elimination of Toxicants and their Metabolites The first topic that was covered by this chapter was the excretion of wastes by the Renal system. The first step that occurs in the kidney deals with the nephron, which is.

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Excretion of most toxicants and their metabolites is by way of the kidneys. Some excretion occurs in the digestive tract and some via milk. Many polar and high-molecular-weight compounds are excreted into the bile. –through their direct discharge into the lumen of the gastrointestinal tract –through excretion in the bile •Toxicants and their metabolites may also be reabsorbed and returned to the liver.

•Biliary excretion is the main route of gastrointestinal elimination of toxicants and their metabolites. Human Elimination of Organochlorine Pesticides: Blood, Urine, and Sweat Study induced perspiration can be used clinically to facilitate decorporation of the range of both parent OCPs as well as their metabolites.

3. Materials and Methods Genuis S. J. Elimination of persistent toxicants from the human body. Human & Experimental. Jan 26,  · Toxicants or their metabolites can be eliminated from the body by several routes.

The main routes of excretion are via urine, feces, and exhaled air. Thus, the primary organ systems involved in excretion are the urinary system, gastrointestinal system and respiratory system.

An introduction to the excretion and elimination of toxicants and their metabolites
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Pesticide Excretion - ScienceDirect