Prostaglandins are part of a class of substances called eicosanoids. Eicosanoids are a group of substances derived from fatty acids and include prostaglandins, thromboxanes, and leukotrienes, all of which are formed from precursor fatty acids by the incorporation of oxygen atoms into the fatty acid chains. This reaction is called oxygenation and is carried out by cyclo-oxygenase enzymes. Prostaglandins and their metabolites have been found in virtually every tissue in the body.
The discovery of prostaglandins and determination of their structure began in 1930, when Raphael Kurzrok and Charles Lieb, both new York gynecologists, observed that human seminal fluid stimulates contraction of isolated uterine muscle. A few years later in Sweden, Ulf von Euler confirmed this report and noted that human seminal fluid also produces contraction in intestinal smooth muscle and lowers blood pressure when injected into the blood stream. It was Von Euler who came up with the name prostaglandin for this mysterious substance. The name prostaglandin seemed appropriate because he thought it originated in the prostate gland. Today, we know that prostaglandin production is not limited to the prostate, in fact, there is virtually no soft tissue in the body that doesn’t produce them. The name, however, has stuck with us through the years. If Von Euler had known his name for prostaglandins would still be with us into the next millennia, I’m sure he would have chosen to name them “Von Eulers” or “UVEs” instead of prostaglandins. By 1960, several specific prostaglandins had been isolated in pure crystalline form and their structures determined. Because our concern with prostaglandins involves primarily PGF2a, and perhaps PGE2, we will not go into detail about the myriad of other prostaglandins. Just know that prostaglandins are abbreviated “PG”. The additional letter and numerical script indicate the type and series. The various types differ in the functional group present in the five-membered ring.
While scientists were studying the structure of these new compounds, other research was being done to determine their role in human physiology and their potential as drugs. Initially these compounds were extremely expensive to synthesize and/or isolate in sufficient quantities for research. In 1969, the price of prostaglandins dropped dramatically with the discovery that the gorgonian sea whip, or sea fan, is a rich source of prostaglandin-like materials. Now however, there is no need to rely on natural sources because chemists have developed highly effective laboratory methods for the synthesis of almost any prostaglandin or prostaglandin analog.
Endogenous production from Arachidonic Acid
Prostaglandins (PGs) are not stored in the tissues of your body. PGs are produced in response to some physiological trigger. The starting material for PG synthesis are unsaturated fatty acids that have 20 carbon structures. The fatty acid that is used to make PGF2a is arachidonic acid.
Functions of prostaglandins in the body
Prostaglandins are classified as autocrine (effecting the same cell that produced it), as well as paracrine (effecting adjacent cells), regulators. They do not really fit into the category of hormones, nor are they neurotransmitters, instead they are simply considered as a corollary of the endocrine system.
The following are some of the regulatory functions of prostaglandins in various organs and systems of the body:
Inflammation & Pain – PGs promote many aspects of the inflammatory response. They are involved in the sensation of pain associated with inflammation and vasoconstriction and/or dilation, and the development of fever. PGs, when injected directly into the hypothalamus, induce fever. Anecdotally, the use of PGF2a also induces a rise in body temperature presumably by interacting with the hypothalamus as well.
Reproductive systems. PGs may play a role in ovulation and corpus luteum function in the ovaries and in contraction of the uterus. Excessive PG production may be involved in premature labor, endometriosis, dysmenorrhea (menstrual cramps), and other gynecological disorders. PGs are often given to induce labor.
Gastrointestinal tract – The stomach and intestine produce PGs. PGs are believed to inhibit gastric secretions and influence gastric motility as well as fluid absorption. Drugs such as aspirin that inhibit prostaglandin production can lead to overproduction of gastric secretion. This predisposes the person to gastric ulcers.
