prostaglandin

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prostaglandin

(prŏs'təglăn`dən), any of a group of about a dozen compounds synthesized from fatty acids in mammals as well as in lower animals. Prostaglandins are highly potent substances that are not stored but are produced as needed by cell membranes in virtually every body tissue. Different prostaglandins have been found to raise or lower blood pressure and regulate smooth muscle activity and glandular secretion. One such substance, which stimulates contraction of the uterus, is used clinically to induce labor; another has been in experimental use as a birth control agent. Prostaglandins also control the substances involved in the transmission of nerve impulses, participate in the body's defenses against infection, and regulate the rate of metabolism in various tissues. Several prostaglandins have been shown to induce fever, possibly by participating in the temperature-regulating mechanisms in the hypothalamus; they also play a part in causing inflammation. The fact that aspirin and other nonsteroidal anti-inflammatory drugs have been shown to inhibit prostaglandin synthesis may account for their usefulness in reducing fever and inflammation. Many naturally occurring prostaglandins as well as many artificial forms have been synthesized in the laboratory.

Prostaglandin

 

in mammals, a hormone that has a broad spectrum of physiological action. Prostaglandins were discovered in human semen by the Swedish scientist U. Euler in 1936. Initially, they were thought to be secretions of the prostate gland (hence the name). They were obtained in a pure form in 1956–65 by Swedish and American scientists.

About 20 natural prostaglandins are known, including thick liquids and low-melting crystalline substances. All prostaglandins are unsaturated hydroxy fatty acids that have a skeleton of 20 carbon atoms. According to their chemical structure, prostaglandins are divided into four groups—A, B, E, and F—E and F prostaglandins being the most important biologically. The subscripts in the formula below indicate the number of double bonds in the lateral chains of the molecule.

Prostaglandins are found in low concentrations (about 1 μg/g) in almost all organs, tissues, and biological fluids of higher animals. The most important physiological effect that is stimulated by prostaglandins is the ability to contract smooth muscles, especially the muscles of the uterus and fallopian tubes; at childbirth and during menstruation, the concentration of prostaglandins in uterine tissues increases substantially. For this reason, they are used in obstetrics and gynecology to facilitate normal labor and to artificially terminate pregnancy in its early stage.

Prostaglandins are also cardiotonics and bronchodilators. Arterial pressure is lowered by A and E prostaglandins and raised by F prostaglandin. A, E, and F prostaglandins intensify coronary and renal blood flow, inhibit gastric secretion, and affect the endocrine glands, including the thyroid gland; they also affect water-salt metabolism by altering the ratio Na+: K+ and blood coagulation by inhibiting the aggregation of thrombocytes.

The biosynthesis of prostaglandins occurs in the cells of different tissues. The precursors of prostaglandins are phospholipids; polyunsaturated fatty acids with a linear chain of 20 carbon atoms are released from phospholipids by the enzyme phospholipase. The oxidative cyclization of the carbon atoms, which occurs with the participation of prostaglandin synthetases (a special system of enzymes), results in the synthesis of E and F prostaglandins.

The classification of prostaglandins as local, or cellular, hormones is justified by their varied functions and the absence of a special organ for their biosynthesis. Their mechanism of action is still unclear. It has been established that prostaglandins affect the activity of the enzyme adenyl cyclase, which regulates the concentration of cyclic adenosine 3’: 5’-monophosphate (cyclic AMP) in the cell. Since prostaglandins influence the biosynthesis of cyclic AMP and since cyclic AMP participates in hormonal regulation, a possible mechanism of action of prostaglandins could consist in correcting (intensifying or weakening) the action of other hormones.

Clinical tests have shown prostaglandins to be promising in the treatment of such conditions as gastric ulcer, asthma, hypertonia, thromboses, arthritides, and inflammations of the nasopharynx. For medical and research purposes, prostaglandins are produced: (1) by enzymatic synthesis based on polyunsaturated fatty acids that are produced in the food-processing industry, (2) by complete chemical synthesis in nine to 13 stages chiefly based on cyclopentadiene, and (3) by partial synthesis in three to five stages based on prostaglandin A2 and E2 derivatives that are present in high concentrations (reaching 1.4 percent of the raw mass) in several varieties of the soft marine coral Plexaura homomalla.

REFERENCES

Markov, Kh. M. “Prostaglandiny.” Uspekhi fiziologicheskikh nauk, 1970, vol. 1, no. 4.
Prostaglandins. New York, 1971. (Annals of the New York Academy of Sciences, vol. 180.)
The Prostaglandins: Progress in Research. Edited by M. M. Karim. Oxford-Lancaster, 1972.

O. S. RADBIL’ and E. P. SEREBRIAKOV

prostaglandin

[‚präs·tə′glan·dən]
(biochemistry)
Any of various physiologically active compounds containing 20 carbon atoms and formed from essential fatty acids; found in highest concentrations in normal human semen; activities affect the nervous system, circulation, female reproductive organs, and metabolism.
References in periodicals archive ?
The most common treatments for primary dysmenorrhea in conventional medicine are nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen, which inhibit the formation of prostaglandins; oral contraceptives; and intrauterine devices (IUDs), which thin the endometrial lining and reduce the amount of prostaglandins being produced.
Foley catheter balloon vs locally applied prostaglandins for cervical ripening and labor induction: a systematic review and metaanalysis.
Molecular modeling suggested that OPP and other pesticides may interfere with prostaglandins by inhibiting cyclooxygenase-1 and cyclooxygenase-2--the enzymes responsible for prostaglandin synthesis--in a manner similar to ibuprofen.
The dose of prostaglandins was one tablet 3mg placed in posterior fornix of vagina, which was repeated 6 hours later if labour did not start caesarean section was performed if induction failed after a period of six hours.
Comparison of microsomal prostaglandin E synthase-1 deletion and COX-2 inhibition in acute cardiac ischemia in mice," Prostaglandins and Other Lipid Mediators, vol.
Cyclooxygenase enzymes and prostaglandins in reproductive tract physiology and pathology.
Prostaglandins are well characterized for their role in many bodily functions - controlling cell growth, constricting and dilating smooth muscle tissue - and a different prostaglandin (F2alpha) is known to increase hair growth.
Sarah Stock note that the findings that intracervical placement of a Foley catheter induces cervical ripening without inducing uterine contractions and is as successful as prostaglandin for inducing labor, could have important implications for women with a prior cesarean section.
Purpose: To report a patient with glaucoma who developed recurrent herpetic keratitis while using two different prostaglandin analogue ophthalmic solutions.
Women were eligible if they were 15-24 weeks pregnant and the fetus had a malformation or chromosomal abnormality;, those with an allergy to prostaglandins, a history of cesarean delivery or hysterotomy, active bleeding, asthma, a deficiency of ammotic fluid or ruptured membranes were excluded.
Many researchers therefore believe the prostaglandins that aspirin and NSAIDs inhibit are involved in the development of cancer.