Sample Essay on Retinol Binding Protein

Retinol Binding Protein

Retinol binding protein can be simply defined as a type of protein that has a low molecular weight and transports retinol or Vitamin A from the liver to the peripheral tissues. However, it should be noted that this class of proteins can also conduct other various functions in the body. In conjunction with retinoic acid, retinol plays an important role in modulating the expression of genes as well as in the overall embryonic development. However, the supply of these substances should always be at a given level since any deficit or excess can have dire consequences that may include malformations in development or even mortality of an embryo.

The retinol binding protein helps in regulating the transportation and metabolism of retinol that is required for successful pregnancy. This class of proteins has been identified in various parts of the body including the embryo, uterus and other tissues like the porcine, ovine and bovine. This is a clear indication that retinol binding protein aids in the proper exposure of retinol to the embryo, and its transportation.

Retinol binding protein is mostly found bound to transthyretin. However, there is usually a small percentage that freely passes through the glomerular membranes. This fraction is re-absorbed by the cells of the renal proximal tubules. Under this circumstance, the small percentage of retinol binding proteins is catabolized. Due to the extensive re-absorption that takes places within the tubules, only small traces of the filtered retinol binding protein is passed out in urine. Thus, it can be said that increased excretion of retinol binding protein during the process of urination points out to an injury or impairment in the proximal tubule.

There are three types of retinol binding protein that you need to take note of when discussing this topic. One of them is called Plasma retinol binding protein that is mainly the vessel of transport in the serum. Cellular retinol binding protein is yet another type whose function is to transport retinol and factors of metabolism to retinyl esters so that they can be stored safely for future use. Besides, the factors of metabolism and retinol can also be transported to form part of retinoic acid.

Cellular retinoic acid binding proteins also fall under the three types of retinol binding proteins. Their work is to bind retinol and retinoic acid with high affinity. Besides, some studies have also indicated that this class of retinol binding proteins can also regulate and supply retinoic acid to nuclear receptors.

Retinol binding proteins are instrumental in the growth and differentiation of several body tissues. Among these, embryos are regarded as the most sensitive to changes in the concentration of retinol. The process through which retinol binding protein produces retinol is still not very clear. Retinol binding protein undergoes synthesis in the liver; however, its secretion depends on the concentrations of retinol. Secretion of RBP is usually blocked whenever there is a deficiency in retinol. This results into a rise in the Retinol binding protein levels in the liver and a fall of the same in the plasma.

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Reference:

http://www.ncbi.nlm.nih.gov/books/NBK6223/

http://en.wikipedia.org/wiki/Retinol_binding_protein