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.
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Comparison of prostaglandin E2 gel, prostaglandin E2 pessary and extra-amniotic saline infusion with oxytocin for induction of labour.
Effects of common pesticides on prostaglandin D2 (PGD2) inhibition in SC5 mouse Sertoli cells, evidence of binding at the COX2 active site, and implications for endocrine disruption.
In our study a total of 183 women with spontaneous PROM confirmed by speculum examination were induced by prostaglandin E2.
Myeloid cell microsomal prostaglandin e synthase-1 fosters atherogenesis in mice," Proceedings of the National Academy of Sciences of the United States of America, vol.
Other experiments showed that prostaglandin E2 could also enhance liver growth and regeneration of liver cells.
Comparative study of extra-amniotic prostaglandin F2 alpha and increasing intravenous oxytocin infusion for termination of pregnancy.
Prostaglandin analoglarinin melanogenezis ve kil folikulu dongusu uzerindeki uyarici etkileri ile irisperiorbital cilt pigmentasyonunda artis ve trikomegali gelistirebildikleri iyi bilinmektedir.
Human papillomavirus E5 protein induces expression of the EP4 subtype of prostaglandin E2 receptor in cyclic AMP response element-dependent pathways in cervical cancer cells.
Researchers found that as PGD2 inhibits hair growth, other prostaglandins work in opposition, enhancing and regulating the speed of hair growth.
Two serious maternal adverse events occurred, both in the prostaglandin group.
Prostaglandin analogue ophthalmic solutions have been used to decrease intraocular pressure (IOP) in patients with glaucoma since the 1990's (1).
He also said that in the post-operative period, it should have been evident to staff at the hospital, once the prostaglandin stopped, that the shunt was not providing sufficient oxygen blood flow.