Prostaglandins contraction

Physiological responses to prostaglandins encompass a variety of effects Some prostaglandins relax bronchial muscle others contract it Some stimulate uterine con tractions and have been used to induce therapeutic abortions PGEj dilates blood vessels and lowers blood pressure it inhibits the aggregation of platelets and offers promise as a drug to reduce the formation of blood clots... 

Prostaglandin F, a hormone that causes uterine contraction during childbirth, has the following structure. Are the two hydroxyl groups (-OH) on the cyclopentane ring cis or trans to each other What about the two carbon chains attached to the ring ... 

Oxytocin is well established as an inducer of labour and is frequently used clinically for this purpose. Oxytocin acts by both direct and indirect mechanisms to stimulate uterine contraction. Firstly, it acts directly on the myometrium to cause uterine contractions and secondly, oxytocin acts to stimulate the production of other mediators of uterine contractions, most notably prostaglandins [8]. 

Many hormones and other blood-borne substances (including drugs) also alter contractile activity of smooth muscle. Some of the more important substances include epinephrine norepinephrine angiotensin II vasopressin oxytocin and histamine. Locally produced substances that may alter contraction in the tissue in which they are synthesized include nitric oxide prostaglandins leukotrienes carbon dioxide and hydrogen ion. 

Prostaglandins F2a and E2 (E. J. Corey) members of a family of hormones that mediate blood pressure, smooth muscle contraction, and inflammation (Section 13.11D). 

A guinea pig ileum bioassay was used to detect and aid in the isolation of a smooth-muscle-contracting substance from the Japanese gorgonian coral Euplexaura erecta [108]. This process led to the isolation of prostaglandin F2a (17) from the MeOH extract of the coral. Its identification was based on comparison with authentic PGF2a and its methyl ester by TLC, and comparison with authentic methyl PGF2a trimethylsilyl ether by mass spectrometry. Because of the nature of the techniques employed, some aspects of the stereochemistry in this isolate of PGF2a remain uncertain. 

Young Referring back to the uterus, we need to remember that the uterus is a secretory tissue and that prostaglandins are produced whenever the subplasmalemmal Ca2+ is raised. One of the effects of the CPA may be to raise the subplasmalemmal Ca2+ and increase the secretion of prostaglandins. By this mechanism the duration and force of the contractions will be increased, possibly without affecting the frequency. 

Arachidonic acid (C20 4 n-6) is the precursor for the synthesis of prostaglandin molecules (Section 4.4.4), which have a wide range of biochemical effects on for example, the perception of pain, inflammation, blood clotting and smooth muscle contraction. Docosahexaenoic acid (DHA, C22 6) and eicosapentaenoic acid (EPA, C20 5) are both n-3 long-chain polyunsaturated fatty acids (PUFA) which have been shown to have significantly beneficial effects on intellectual development and inflammatory conditions such as asthma and cardiovascular disease. 

Aizawa, H., Inoue, H., Matsumoto, K., Koto, H., Nakano, H., and Kara, N. (1996) Thromboxane A antagonist inhibits leukotriene D -induced smooth muscle contraction in guinea-pig lung parenchyma, but not in trachea. Prostaglandins Leukot. Essent. Fatty Acids. 55,437-440. 

Prostaglandins are involved, along with oxytoxin and steroids, in control of parturition. They result in contraction of the uterine muscles and dilation of the cervix (the neck of the womb). This effect is very powerful since the maximum dilation is an increase in diameter of about 10 cm. Prostaglandins were first used for induction of abortion in the UK in 1972. 

Seminal vesicles Fructose Prostaglandins Potassium ions Fuel for sperm Not known but may stimulate contractions of smotth muscle in wahs of vagina and uterus Required by glycolytic enzymes... 

These messengers also play a role in regulating contraction of myometrium, which consists of smooth muscle fibres. Contraction is controlled by increases in the concentration of cytosolic Ca ions. Prostaglandins activate Ca ion channels in the plasma membrane of the fibres oxytocin activates release of Ca from intracellular stores. The increase in concentration of Ca ions leads to activation of myosin light-chain kinase which leads to crossbridge cycling and contraction (as described in Chapter 22 Figure 22.12). 

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