Abortion – The Role of Prostaglandins in Abortion

Abortion  – The Role of Prostaglandins in Abortion

Abortion – Prostaglandins can be defined as a type of “Eicosanoids” and eiscosanoids are a group of compounds derived from certain polyunsaturated fatty acids (principally arachidonic acid). Eicosanoids are so called because they are essential fatty acids (membrane phospholipids) derived from carbon twenty (C20)carbon skeleton and contain three, four or five double bonds, they can also possess a 5- carbon ring in its structure.

Prostaglandins are not hormones but autocrines (or paracrines) which are locally acting messenger molecules. They differ from hormones in that they are not produced at a discrete site but in many places throughout the human body. Their target cells are present in the immediate vicinity of the site of their excretion. They are produced by virtually all nucleated cells apart from lymphocytes; these autocrine, paracrine lipid mediators, act upon platelets, endothelium uterine and mast cells. (Nicolaou K.C. and E.J. Sorensen 1996) and (Nelson R. 2005).

Prostaglandins were first discovered and isolated from human seminal fluid in the year 1935 by the Swedish Physiologist Ulf Von Euler, thinking they had come from prostate gland he named them prostaglandins. It has since been determined that they exist and are synthesized in virtually every cell of the body. Prostaglandins are said to be hormone–like in the sense that the undergo Autocrine signaling which is a form of signaling where by the cell secretes a chemical messenger (called the autocrine agent) that binds to autocrine receptors on the same cell, leading to changes in the cell. An example of an autocrine agent is the cytokine interleukin- I in the monocytes. When interleukin-I is produced in response to external stimuli, it can bind to cell-surface receptors on the same cell that produced it. (Nelson R., 2005)

FUNCTIONS OF PROSTAGLANDINS (Some basics)

These ‘local’ hormones have a variety of physiological effects on the body including;

• Activation of the inflammatory responses at the sites of damaged tissue, and production of pain and fever. When tissues are damaged, white blood cells flood the site to try to minimize destruction. Prostaglandins are produced as a result.
• Blood clots from when a blood vessel is damaged. A type prostaglandins called thromboxane stimulates construction and dotting of platelets. Also the opposite happens and prostaglandins I2 (PGI2) are produced on the walls of blood vessels where clots should not be forming. The body is very, very clever, it knows what to do, where to do it and when.
• Certain prostaglandins are involved with the introduction of labour and other reproductive processes and the play a role in fertility. PGE2 causes uterine contractions and has been used to induce labour.
• Prostaglandins are involved in several other organs and systems such as the gastrointestinal (GI) tract, cell growth and the immune system response.

However, this write up centers its interest on the role and involvement of prostaglandin in the induction of labour and other reproductive processes. Abortion on the other hand, is also a form of removal or expulsion of a fetus or embryo from the uterus with intension of terminating it.

Abortion can occur spontaneously or induced; spontaneous abortion is said to be the expulsion of an embryo or fetus due to accidental trauma or natural causes before and approximately the 22^nd week of gestation. It is also known as “miscarriage”. Induced abortion on the other hand, is the intentional removal (expulsion) of an embryo or fetus for therapeutic or elective reasons.

(Shad, I. and Ahuman, E., 2009). There are several methods of achieving this method of abortion but Medical and Surgical methods are the two main categories. Surgical abortion has to do with the use of surgical apparatus or machines to aid the process, while Medical abortion which is a non–surgical method of abortion involves the use of pharmaceutical drugs in the achievement of the process. Prostaglandin and its analogs, drugs synthesized from prostaglandins, natural roots and herbs (of plant origin) and many others have shown to be effective in their use (therapeutic) as “Abortifacients” and/(or) for promotion of labour, which is the hallmark of these seminar work.

 ABORTION

Abortion can be defined as the termination of a pregnancy by the removal or expulsion of a fetus or embryo from the uterus, resulting in or caused by its death. [(Shah, I. and Ahman, E. (2009)]

The Dictionary defines it as the removal of an embryo or fetus from the uterus in order to end a pregnancy, the arrested development of an embryo or an organ at a more or less early stage. (Dictionary. Com. 2006)

Abortions can occur in several ways spontaneously due to complications during pregnancy or can be induced. In the context of human pregnancies, abortion is sometimes interchanged or used in place of elective abortion which is the termination of a pregnancy for all reasons apart from therapeutic reasons (an abortion done or induced to preserve the health of a gravida (pregnant female)), while spontaneous abortions are  usually  termed miscarriage. (Shah, I. Ahman, E., 2009)

Abortion has along history and has been induced by various methods including herbal abortifacients, the use of sharpened tools, physical trauma, and other traditional method. Contemporary medicine utilizes medications and surgical procedures to induce abortion. The legality, prevalence and cultural views on abortion vary substantially around the world including Nigeria. In many parts of the world there is prominent and divisive public controversy over the ethical and legal issues of abortion, For instance the united state of American (USA).

Abortion and abortion related issues feature prominently in the national politics in many nations, often involving the opposing pro-life and pro-choice world wide social movements (both self-named). Incidence of abortion has been observed to   decline worldwide as a result of access to family planning education and contraceptives.

TYPES OF ABORTION

Scientifically, abortion has been able to be divided into two (2) different types which are

1. Spontaneous
2. Induced

SPONTANEOUS ABORTION

This is also known as miscarriage and can be defined as the expulsion of an embryo or fetus due to accidental trauma or natural causes before approximately the 22nd week of gestation, most miscarriages are due to incorrect replication of chromosomes. They can also be caused by environmental factors such as temperature, electromagnetic radiation and so on.

A pregnancy that ends before 37 weeks of gestation resulting in a live-born infant is known a “premature birth”. When a fetus dies in- utero after about 22 weeks or during delivery it is usually termed “still born”. Both cases are not generally considered as miscarriage although the usage of these terms can sometimes over lap. Between 10%-50% of pregnancies and in clinically apparent miscarriages depending upon the age and health of the pregnant woman. Most miscarriage occurs very early in pregnancy, in most cases, they occur so early in that the pregnant woman is not even aware that she was pregnant. One study testing hormones for ovulation and pregnancy found that 61.9% of conceptuses were lost prior to 12 weeks and 91.7% of these losses occurred subclinically, without the knowledge of the once pregnant woman.

The risk of spontaneous abortion decrease sharply after the 10^th week from the last menstrual period (LMP). Another study of 232 pregnant women showed virtually complete pregnancy loss by the end of the embryonic period” (10 weeks LMP) with a pregnancy loss rate of only 2 percent after 8.5weeks LMP. The most common cause of spontaneous abortion during the first trimester is chromosomal abnormalities of the embryo or fetus, accounting for at least 50% of sampled early pregnancy losses. Other causes include vascular disease (such as lupus), diabetes, other hormonal problems, infection and abnormalities of the uterus. Advancing maternal age and a patient history of previous spontaneous abortions are the two leaching factors associated with a greater risk of spontaneous abortion. A spontaneous abortion can also be caused by accidental trauma, intentional trauma or stress to cause miscarriage is considered induced abortion or feticide.

INDUCED ABORTION

Induced abortion can also be referred to as intentional abortion. A pregnancy can be intentionally aborted in many ways. The choice of procedure or manner in which the pregnancy is removed, chiefly depends upon the gestational age of the embryo or fetus which increase the size as the pregnancy progresses. Legality, regional availability, Doctor-patient relationship, age of gravida are some of the factors to be considered when choosing specific procedures for abortion. Reasons for procuring induced abortions are typically characterized as either therapeutic or elective. Therapeutic abortions are done or performed to;

• Preserve the woman’s physical or mental health
• Save the life of the pregnant woman.
• Terminate pregnancy that would result in a child born with a congenital disorder that would be fatal or associated with significant morbidity or selectively reduce the number of fetuses to lesson health risks associated with multiple pregnancies.

An abortion is referred to as elective when it is performed at the request of the woman for reasons other than maternal health or fatal disease.

METHODS USED IN INDUCED ABORTION

There are 2 methods, depending on the gestational age in which abortion may be performed. They are

• Medical Abortion
• Surgical Abortion

MEDICAL ABORTION

Medical abortions are non- surgical abortions. In medical abortions, “abortifacients” are used and they are substances that induce abortion. Abortifacients for animals that have mated undesirably are known as “mismating shots”. Some include mifepristone, which is typically used in conjunction with misoprostol in two step approach. When an abortifacient is used orally it may be referred to as the abortion pill.

Abortifacients are of 2(two) categories, the

• Pharmaceutical abortifacients
• Herbal abortifacients

        PHARMACEUTICAL ABORTIFACIENTS

These involve the use of Pharmaceutical drugs to, abortion purposes. Prostaglandin analogues such as misoprostol or gemeprost (both synthesis prostaglandin E, (PGE1) analogues) are often used to terminate pregnancy up to 24 or 60 days of gestation in combination with mifepristone (A progesterone receptor antagonist) or methotrexate (an antifolate). Misoprostol is approved in France for use with mife pristone for medical abortion. Mifepristone is used in conjunction with a prostaglandin-analogue. Misoprostol alone is sometimes used for self-induced abortion in Latin America Countries where legal abortion is not available and by some people in the United States who cannot afford a legal abortion. (Rod flower, Humphery, P. Rang, Maureen, M. Dale, Ritter and James, M. 2007) Rang and Dale Pharmacology. Edinburgh, Churchill living stone).

• Misfepristone: is a synthetic steroid compound used as a pharmaceutical. It is a progesterone receptor anatagonist used as an abortifacient in the first two months of pregnancy and in smaller doses as an emergency contraceptive.

IUPAC NAME: 11,β – (P-(Dimenthy lamino) phenyl)-17β- hydroxyl (-17-(1-propynyl)Estra-4, 9-dien-3-one.

• Formular: C29H35 NO2
•  Metabolism: Hepatic
• Half life: 18hrs

(Rang, A.P. (2003) pharmacology (5^th edition) Edinburgh: Churchill Living stone pp234)

• Dinoprostone: A synthesis preparation of PGE₂ is administered vaginally for oxytocic use. In the USA, it is approved for inducing abortion in the second trimester of pregnancy for missed abortion,for benign hydatidiform mole and for ripening of the cervix for induction of labor in patients at or near term.

Dinoprostone

(Prostaglandin E₂, PGE₂  )

Dinoprostone stimulate the contraction of the uterus throughout pregnancy. As the pregnancy progress, the uterus increases its contractile response, and the contractile effect of oxytocin is potentiated as well. Dinoprostone also directly affects the collagenase of the lymphatic system. Dinoprostone is metabolized in local tissues and on the first pass through the lungs (about 95%). The metabolites are mainly excreted in the urine. The plasma half-life is 2.5-5 minutes.

Another pharmaceutical drug that can be used for medical abortion is carboprost tromethamine.

 HERBAL ABORTIFACIENTS

          Many herbs and plants used by herbalists contains chemicals which act as abortifacients if taken in certain doses or mixtures.

E.g. Bitter melon

Wild carrot

Nut Meg

Brewers yeast

Penny royal

(Riddle, John M. (1992). Contraception and Abortion from the Ancient world to the Renaissance, Cambridge, MA: Harvard University press).

DAUCUS CAROTA

An Angiosperm in the order, family and Genus of Apiales, Apiaceae and Daucus respectively, with a specie name of D. carota can be found in regions like Europe, South west Asia and naturalized to northeast, North America. Daucus carota is a variable biennial plant, usually growing up to 1m tall flowering from June to August. Very similar in appearance to the deadly poison hem lock, Daucus carota is distinguished by a mix of bi- pinnate and tri-pinnate leaves, fine hairs on its stems and leaves, a root that smells like carrots, and occasionally a single dark red flower in its center.

USES

Like the cultivated carrot, the wild carrot root is edible while young. But quickly becomes too woody to consume. A teaspoon of crushed seeds has long been used as a form of birth control; its use for this purpose was first described by Hippocrates over 2000 years ago. Research conducted on mice has offered a degree of confirmation for this use, wild carrot was found to disrupt the Ovum implantation process, which reinforce its reputation as a contraceptive Chinese studies have also indicated that the seeds block ‘Progesterone synthesis’ which could explain this effect.

Note: caution should be taken when handling this plant because its leaves can cause “phytophotodermatitis”.

(Chaudhury, R. (1993). “The quest for a herbal contraceptive” Natel Med. J. India 6 (5); 199-201. )

BITTER MELON

Momordica charantia called bitter melon or bitter gourd in English is a tropical and sub tropical of the family cucurbitaceae widely grown in Africa Asia and the Caribbean for its edible fruit; which is among the most bitter of al fruits. They differ in shape and bitterness of the fruit.

This he baceous tendril – bearing vine grows to 5 meters it bears simple, alternate leaves 4-12 cm across, with 3-7 deeply separated lobes. Each plant bears separate yellow male and female flowers. Flowering occurs during June to July and fruiting during September to November. It has a distinct warmly exterior and an oblong shape. It is hallow in cross- section with a relatively thin layer of flesh surrounding a central seed cavity filled with large flat seed and pith. It is most often eaten green or as it is beginning to turn yellow. The skin is tender and edible seeds and pith appears white in unripe fruits; they are not intensely bitter and can be removed before cooking.

USES

This plant has various uses both medically and other wise among which are, Digestive acid (treat dyspepsia and constipation), Antihelmintic (treat gastrointestinal disease), Antimalarial (due to its content of quinine), Antiviral (such as chickenpox and measles), Diabetes mellitus type2, fevers, Burns, painful menstruation, Abortifacient for birth control and to help child birth.

[(J.K. Grover and S.P. Yadav (2004)], pharmacological actions and potential uses of Momordica charantia, a review, Journal of Ethnopharamacology volume 93, issue1, page 123-32)

SURGICAL ABORTION

Surgically induced abortion as the name implies involves the use of surgical methods in the process of abortion. In these methods machines are used as aids in the process, some of these methods include

• Manual vacuum Aspiration (MVA)
• Electric Vacuum Aspiration (EVA)
• Dilation and curettage (D$C)

MANUAL VACCUM ASPIRATION (MVA)

These methods consist of removing the fetus or embryos placenta and membranes by suction using a manual syringe, while the process goes on, cervical dilation is not required.

ELECTRIC VACCUM ASPIRATION (EVA)

These methods uses electric pump and is suitable for early pregnancy. The machine in inserted through the virgina into the uterus via the cervix. It is however important to note that Dilation and evacuation is another method suitable for pregnancies within 15th to 26th weeks. It consists of opening the cervix of the uterus and emptying it using surgical instruments and suction.

DILATION AND CURETTAGE (D and C)

The second most common method of abortion is a standard gynecological procedure performed to a variety of reasons, including examination of the uterine living for possible malignancy, investigation of abnormal bleeding and abortion.

Curettage refers to cleaning the walls of uterus with a curette. WHO (World Health Organization) recommends this procedure, also called sharp curettage; only when MVA is not available.

After 16th week of gestation, abortions can be induced by intact dilation and extraction (IDE) (also called intrauterine cranial decomposition), which require surgical decompression of the fetus head before evacuation. It is sometimes called “partial–birth abortion”.

A Hysterotomy abortion is a procedure similar to a caesarean section and is performed under general anesthesia. A smaller incision is required unlike the caesarean section and this method is used during later stages of pregnancy.

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This article was extracted from a Seminar Research Work/Material Topic “THE ROLE OF PROSTAGLANDINS IN ABORTION”