Prostaglandins

Prostaglandin's definition includes a category of physiologically active lipid molecules known as eicosanoids. In simpler words, prostaglandins are a group of lipids (eicosanoids). Prostaglandins functions have been discovered to have a variety of hormone-like actions in animals. In humans and other animals, prostaglandins may be found in practically every tissue. Enzymatically, they are made from the fatty acid arachidonic acid. There are 20 carbon atoms in each prostaglandin, including a 5-carbon ring. They belong to the prostanoid family of fatty acid derivatives and are a subclass of eicosanoids. 

In 1935, Swedish physiologist and Nobel Prize winner Ulf von Euler and British physiologist M. W. Goldblatt independently found them in seminal fluid. Ulf von Euler, a Swedish scientist, found prostaglandins in human sperm in 1935 and called them after assuming compounds were released by the prostate gland. The pioneering research of Swedish biochemists Sune K. Bergström and Bengt Ingemar Samuelsson, as well as British biochemical Sir John Robert Vane, enhanced our knowledge of prostaglandins in the 1960s and 1970s. In 1982, the three of them won the Nobel Prize in Physiology or Medicine for their work isolating, identifying, and analysing a variety of prostaglandins.

The article focuses on the discussion of what are prostaglandins and prostaglandins function. The article also answers questions like why PG is referred to as prostaglandin hormone, the uses of prostaglandins. The types and prostaglandin action are also discussed in the article. 

Synthesis of Prostaglandins

Since we have understood what are prostaglandins including the prostaglandins definition, let us discuss the synthesis of the prostaglandin hormone in the human body. Numerous tissues in the body contain prostaglandins. Nearly every single nucleated cell produce them. Arachidonic acid, a fatty acid is the precursor of prostaglandins synthesis. Arachidonic acid is an essential element of phospholipids, which are crucial molecules of the plasma membrane. A series of events are put in action in response to a wide range of stimuli, encompassing hormonal, chemical, and physical factors, resulting in prostaglandin production and release. These triggers cause an enzyme known as phospholipase A2 to be activated, either directly or indirectly. The discharge of arachidonic acid from phospholipid molecules is catalysed by this enzyme.

Arachidonic acid can take one of several different paths depending on the type of stimuli and the enzymes present. Lipoxygenase is an enzyme that catalyses the conversion of arachidonic acid to one of many leukotrienes, which are essential mediators of the inflammatory process. Cyclooxygenase is another enzyme that catalyses the conversion of arachidonic acid to one of many endoperoxides. Prostaglandins, prostacyclin, and thromboxanes are formed when the endoperoxides are further modified. In the process of blood coagulation, thromboxanes and prostacyclin play critical roles.

Prostaglandins Function

Since we have learnt what are prostaglandins and the synthesis of the prostaglandins along with the different types of prostaglandins. Let us look into the main functions or the uses of prostaglandins which are summarised below.

• Prostaglandins play an important role in the synthesis of eicosanoids hormones

• Prostaglandin hormone also acts on the thermoregulatory centre of the hypothalamus to produce fever

• Prostaglandins are released during menstruation, due to the destruction of the endometrial cells, and the resultant release of their contents.

• Prostaglandins also play an important role in vasodilation and blood clotting.

• Prostaglandin hormones are responsible for inflammation.

Since we have seen all the main prostaglandins function or the uses of the prostaglandin let us discuss some of the main functions of the prostaglandin hormone in detail.   

Vasodilation

Most prostaglandins have a local effect; for example, they are potent vasodilators. Vasodilation happens whenever the muscle fibres that line the insides of blood vessels relax, allowing the vessels to expand. This reduces blood frictional resistance, allowing blood flow to enhance and blood pressure to drop. The kidneys are a good illustration of prostaglandins' vasodilatory activity, as broad vasodilation increases blood flow to the kidneys and salt excretion in the urine. Thromboxanes, on the other hand, are potent vasoconstrictors that cause blood flow to drop and blood pressure to rise.  

Blood Clot

In the development of blood clots, thromboxanes and prostacyclins play a critical part. The creation of a clot starts with the clumping of blood platelets. Prostacyclin inhibits and thromboxanes greatly enhance this activity. Prostacyclin is produced in the walls of blood arteries and has the biological function of minimizing the production of unnecessary clots. Thromboxanes, on the other hand, are generated inside platelets and released to stimulate clot formation in response to artery damage, which induces platelets to attach and function as parturition walls of blood arteries.

Platelet adhesion is higher in arteries that have been compromised by atherosclerosis. Platelets aggregate form a plaque termed a thrombus along the internal surface of the vessel wall in afflicted vessels. A thrombus can partially or fully obstruct (occlude) blood flow through a vessel, or it might break free from the vessel wall and migrate through the circulation, causing an embolus. An embolism occurs when an embolus becomes stuck in another channel and fully obstructs blood flow. The most prevalent causes of heart attacks are thrombosis and emboli (myocardial infarction). For patients who are at high risk of heart attack, modest doses of aspirin (a cyclooxygenase inhibitor) daily have shown some efficacy as a preventative therapy.

Muscle Contraction

Prostaglandin action is also seen in muscle contraction, this is critical in the female reproductive system. Prostaglandins are involved in ovulation and increase uterine muscular contraction, which led to the effective treatment of menstrual cramps with prostaglandin synthesis inhibitors like ibuprofen. Prostaglandins are also used to induce therapeutic abortions and have a function in triggering labour in pregnant women at term. 

Prostaglandins influence the function of the digestive system by activating or inhibiting the contraction of the smooth muscles that line the intestinal walls. Furthermore, because prostaglandins restrict stomach acid release, it's not unexpected that medicines that block prostaglandin production, such as aspirin, can cause peptic ulcers. Prostaglandin activity on the digestive system can induce severe watery diarrhoea and may modulate the effects of cholera toxin and vasoactive intestinal polypeptide in Verner-Morrison syndrome.

Increased or Decreased Concentration of Prostaglandins 

Since prostaglandin functions as a hormone and plays some of the critical roles in the body, let us look into the consequences of increased or decreased concentration of the prostaglandin hormone. Prostaglandins are created in high amounts in reaction to infection, causing inflammation and the indications of erythema, oedema, pain, and warmth. This is a crucial step in the body's natural healing process. However, this typical reaction can occasionally result in the excessive and prolonged synthesis of prostaglandins, which can cause undesired inflammation and contribute to a variety of disorders. This means that medications that target cyclooxygenase-2 can be utilised to treat a variety of ailments. Anti-inflammatory medications like aspirin and ibuprofen lower prostaglandin levels by preventing the function of cyclooxygenase enzymes. This is how these medications operate to alleviate inflammatory symptoms. Aspirin also inhibits the synthesis of thromboxane, therefore it can be used to avoid blood clots in cardiac diseases.

As we have discussed the consequences of a high concentration of the prostaglandin hormone in the body let us look into the case where the concentration drops from the normal level. In such conditions of decreased concentration, the metabolism or functions mediated by prostaglandins gets hindered this is especially seen in the case of pregnancy where muscle contraction is important for parturition. Under specific conditions, manufactured prostaglandins can be utilised to raise prostaglandin levels in the body. Prostaglandins, for example, can be used to induce labour towards the conclusion of pregnancy or to induce abortion in the instance of undesirable pregnancy. They can also be used to treat newborn neonates with stomach ulcers, glaucoma, and congenital heart problems. Further research on how prostaglandins operate might lead to newer therapies for a variety of ailments.

In conclusion, we have seen what are prostaglandins, the synthesis of the hormone. We have also seen the prostaglandin actions concerning different functions, the impact of increased or decreased concentration of the hormone is also discussed in the hormone.