Lipophilic Compounds example essay topic

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 the functional unit of the kidney. In the glomerulus the formation of urine begins with the passive filtration of plasma through the pores that are found in the glomerulus. The plasma is forced through these pores by hydrostatic pressure.

The only things that determines if a molecule will pass through the pores of the glomerulus is it's molecular weight. The lower the molecular weight, the easier it will pass through the pores. Another determining factor will be if a molecule is bound to a large molecule. If this is true then passage through the pores will be hindered by the size of the larger molecule. Reabsorbtion of the many ions, minerals and other nutrients that escaped in the filtrate will need to be recovered...

Reabsorbtion begins in the tubules of the nephron. Anywhere from 65% to 90% of reabsorption occurs in these structures. Active reabsorption is used to recapture glucose, proteins, amino acids and other nutrients. Water and chloride ions are passively reabsorbed by the establishment of osmotic and electrochemical gradients. Both the Loop of Henley and collecting duct are used to establish these. The tubule has a brush border that will absorb proteins and polypeptides through.

These molecules are sometimes and converted into amino acids. and returned to the blood. Sometimes the accumulation of these proteins can lead to renal toxicity A second process that occurs in the tubules is tubular secretion. This is another mechanism used to excrete solutes. Secretion may be either passive or active. Secretions include organic bases, which occur in the pars rect a of the proximal tubule. Secretions of weak bases and two weak acids occur passively.

Other mechanisms involves the use of a mechanism that is called ion trapping. Ata certain pH the compounds are more ionized. Outside of the tubule these compounds are non-ionized and are lipophilic. Thus they are able to diffuse across the membranes of the tubule. Once inside, the pH of the tubule will ionize them and render then unable to pass across the cell membranes. The removal of is dependant on many factors.

First is the polarity of the. Polar compounds are soluble in the plasma water are more easily removed by the kidneys through the use of filtration. The faster the rate of filtration, the faster the polar are eliminated from the body. Other factors that affect the rate of elimination include: dose of the, the rate pf absorption, and the ability to bind to proteins as well as the polarity of the compound. In comparison lipophilic compounds will cross the cell membrane with more ease. Due to their properties they will follow the their concentration gradient across the membrane of the tubules and are, therefore, easily retained by the body.

If a lipophilic compound is metabolized to a more polar state then it is more easily metabolized. Another important factor that will determine excretion by the kidneys will be the pH of the environment. Those compounds that are effected by pH will have both an ionized and non ionic form. When in their non ionized form it will reabsorbed by the tubules and kept their because of their change to an ionized form. The liver is the second most important organ that is involved in the removal of wastes from the body. The primary method of excretion involved the Hepatic cells of the liver.

Both passive and active modes of transport are used. Bile is excreted by the hepatic cells. It is a concentration of that will aid in the transport of lipids from the small intestine. Before reaching the small intestine, via the common bile duct, it will be stored and concentrated in the gall bladder. The bile will then be reabsorbed by a process known as circulation. The more lipophilic or non ionized a compound is, the more readily it will be absorbed.

Solubility is another factor that will determine absorbance. The rapid absorbance of these compounds does not mean that they will not be readily excreted. Some compounds are readily excreted after absorption. Most toxic are very lipophilic. This means that they will be easily absorbed and dispersed among the tissue. Their characterizations also means that there excretion in either the urine or bile will be in very small amounts, unless they are metabolized ito more polar compounds.

One of the methods used to dispose toxic lipophilic's is by degradation of the large compounds into small polar fragments that can be eliminated through the urine or bile. Oxidative metabolism of toxic cyclic and polycyclic hydrocarbons is done with the introduction of a hydroxyl group into the ring structure. The excretion of halogenated hydrocarbons is extremely difficult. Their accumulation in the body occurs in both adipose tissue and lipid layers of the skin. They will stay there for the duration of the animals life time. The molecular weight of a compound will determine if the compound will be excreted in the urine or feces.

Any elimination of a will be done in association with the excretion of another compound that is normally eliminated by the body. Most gaseous and volatile are eliminated through the lungs. The rate of excretion is based on how soluble the compound is in the blood, the rate of volume of respiration, and the rate of blood flow to the lungs. Second method used is the transport mechanism.

Which will involve the use of the muco ciliary broncho tracheal escalator that will end with the material being swallowed and passed out of th body. Sex linked elimination is restricted to the female. The milk excreted by the mother will contain the largest number of possible. The elimination of the is dependant on the half-life of the compound. Most of the compounds that are excreted are low in dosage and therefore are not lethal. Chronic exposure can be toxic to the nursing young.

The type of materials that are excreted are lipophilic because they are not excreted by the other major pathways. In eggs the type of compound eliminated are also in nature. Fetuses are mostly effected by lipophilic compounds that are able to pass the placental barrier. There are cases of fatal exposure of to the fetus through the mother.