Prostaglandins belong to the family of lipid. Soluble unsaturated hydroxyl acid containing twenty carbon (c) atoms and based on the prostanoic acid skeleton. There are two main types of Prostaglandins (PGs), the E and F series each having 3 members E1, E2, E3 and F1σ, F2σ, F3σ. The other PGs are known as secondary PGs and are products of enzymic or chemical dehydrations of PGEs e.g PG+2, PGA2, PGD2 and PGB. Prostaglandins are probably the most important regulators of female productive functions (ovulation, uterine receptivity, Implantation and parturition) and associated with pathologies (pain, fever, and inflammation), apart from sex steroids. Prostaglandins are not stored in tissues but are synthesized and released in response to a given stimulus. Prostaglandins are produced by all nucleated cells of the body and act locally in a paracrine (locally active) or autocrine (acting on the same cell from which it is in a synthesized) fashion. Prostaglandins are therefore regarded as essential mediators of female reproductive processes, hence, this paper seeks to review the role of Prostaglandins which is exploited in livestock production especially oestrus synchronization and induced parturition.KEYWORDS: Prostaglandins, Production, Role, Livestoc

Bassey, A.E.

Ibom, L.A.

Okon, B

Okon, F.I.

English

AJOL - African Journals Online

DOI: http://dx.doi.org/10.4314/gjass.v15i1.5GLOBAL JOURNAL OF AGRICULTURAL SCIENCES VOL. 15, 2016: 27-30COPYRIGHT© BACHUDO SCIENCE CO. LTD PRINTED IN NIGERIA ISSN 1596-2903www.globaljournalseries.com, Email: info@globaljournalseries.comTHE ROLE OF PROSTAGLANDINS IN LIVESTOCK PRODUCTIONB. OKON, L. A. IBOM, A. E. BASSEY AND F. I. OKON(Received 5 May 2015; Revision Accepted 17 September 2015)ABSTRACTProstaglandins belong to the family of lipid. Soluble unsaturated hydroxyl acid containing twenty carbon (c) atoms andbased on the prostanoic acid skeleton. There are two main types of Prostaglandins (PGs), the E and F series eachhaving 3 members E1, E2, E3 and F1σ, F2σ, F3σ. The other PGs are known as secondary PGs and are products ofenzymic or chemical dehydrations of PGEs e.g PG+2, PGA2, PGD2 and PGB. Prostaglandins are probably the mostimportant regulators of female productive functions (ovulation, uterine receptivity, Implantation and parturition) andassociated with pathologies (pain, fever, and inflammation), apart from sex steroids. Prostaglandins are not stored intissues but are synthesized and released in response to a given stimulus. Prostaglandins are produced by allnucleated cells of the body and act locally in a paracrine (locally active) or autocrine (acting on the same cell fromwhich it is in a synthesized) fashion. Prostaglandins are therefore regarded as essential mediators of femalereproductive processes, hence, this paper seeks to review the role of Prostaglandins which is exploited in livestockproduction especially oestrus synchronization and induced parturition.KEYWORDS: Prostaglandins, Production, Role, LivestockINTRODUCTIONProstaglandins were first discovered andisolated from human semen in the 1930s by Ulf VonEuler of Sweden. Thinking they had come from theprostrate gland, he named them Prostaglandins.Prostaglandins are like hormones in that they act aschemical messengers, but do not move to other sites,but work right within the cells where they aresynthesized (Ophardt, 2003). Von Euler (1937) alsostated that biologically active lipids in human seminalplasma were first detected and called Prostaglandins.Despite their name, Prostaglandins are synthesized andstored in the seminal vesicle prior to ejaculation withtestosterone being the stimulus for Prostaglandinssynthesis.Prostaglandins is a major lipid mediatorsynthesized from arachidonic acid via the catalyticactivities of cyclooxygenase (cox) and Karim (1976) withOlson (2003) pointed out that, there are different typesof Prostaglandins  ranging from PGE, PGF, PGI2, PDG2,PGH2. The PGEs and PGFs are known as primaryProstaglandins with each having three members E1, E2,E3 and F1σ, F2σ and F3σ. Others are secondaryProstaglandins formed as a result of PGEs. Thesebiologically active substances are said to occur in allmammalian tissues in the body with lungs, liver, kidneyand placenta being the major organs of metabolism.Although it is clear that Prostaglandins play animportant role in a number of reproductive processes;Clark and Myatt (2008) also added that Prostaglandinsproduced in the female are necessary for severalreproductive processes and are involved from theearliest events (i.e Luteinizing hormone release) throughovulation and up to the final event which leads tosuccessful parturition.This review work is to outline the role ofProstaglandins which is exploited in livestockreproduction especially in oestus synchronization andindeed parturition.Reproductive EffectsProstaglandins specifically PGF2σ stimulateactivity of the uterus during pregnancy. This has foundpractical application in the induction or expulsion of theproducts of conceptus viz the fetus and palcenta.According to Karim (1976), only small quantities of thePGs are required, either intravenously or by introductiondirectly into the uterine cavity, to produce abortion. Inaddition, both the in-vitro and in-vivo PGF2σ produceleutolysis of a functional Corpus luteum and canfacilitate interruption of pregnancy by the reduction inblood level progesterone.Oestrus cycleBlatchley et al., (1975) pointed out that asignificant increase in the output of oestrodiol from theovary at oestus stimulates the secretion of the luteinizinghormone from the anterior pituitary gland. The luteinizinghormone (LH) which causes ovulation and thetransformation of the ovulated follicle into a Corpusluteum, is also involved in the secretion of progesterone27B. Okon, Department of Animal Science, University of Calabar, Calabar, Cross River State, Nigeria.L. A. Ibom, Department of Animal Science, University of Calabar, Calabar, Cross River State, Nigeria.A. E. Bassey, Department of Animal Science, University of Calabar, Calabar Cross River State, Nigeria.F. I. Okon, College of Health Technology, Cross River State, Calabar, Nigeriain-vivo. An exception occurs in rats where a fullyfunctional release of prolactin occurs as a result ofcoitus. Regression of the Corpus luteum terminatesprogresterone production and a new cycle begins.Luteinizing Hormone (LH) ReleaseCarlson et al., (1977), administering PGF2σ tosheep during the luteal phase of the cycle obtained anincrease in the plasma concentrations of LH. Therelease of LH caused by oestradiol in anoestrus sheepis prevented by indomethacin (an inhibitor of PGsysnthesis). In sheep also, an increase in PGF2σ outputfrom the brain is associated with induced oestradiolincrease in LH release. This output is pulsatile like theoutputs of luteinizing hormone releasing hormone(LHRH) and LH.Conversely, Hams et al., (1974) noted thatPGE2 stimulates the release of LH when injected intothe third ventricle of the brain at the anterior pituitarygland in pre-vestrous and ovariectomised rats treatedwith oestradiol. PGE2 actually stimulates LH release bycausing the release of LHRH and not by acting directlyon the pituitary gland.OvulationOvulation has three major phases in whichProstaglandins may be involved.(1) Follicular maturation(2) Rupture of the follicle(3) Formation of the Corpus luteumLa Maire and associates showed that isolatedfollicles could be stimulated with human chorionicganadotropin (HCG) to increase their PGE and PGF2σlevels (Le Marie et al., 1973). This increase onlyoccurred in those follicles destined to be ovulated. Pre-treatment of animals with Prostaglandin synthesisinhibitors blocks ovulation (Zanagno et al., 1999).Apparently, PGs cause ovulation by increasingcollagenolysis through activating collagenase. Thisincrease in collagenolysis causes “thining” of thefollicular wall at the apex of the follicle resulting ineventual rupture of the follicle and release of ovum(Downs and Longe, 1983).Stimulation of Progesterone secretionProgesterone secretion by Corpus luteum in theovary in many species is stimulated by PGE2 and PGI2.The actions of these PGs is mediated by cyclic AMP.Consequently in this respect, these PGs act as LHmimics.A detailed study carried out in sheep has shownthat the intra-follicular injection of indomethacin preventsovulation but does not prevent luteinization of the follicleinto a structure which secretes normal amounts ofprogesterone (Merdock and Dunn, 1983).Although PGs mediate ovulation induced by LH,they are not involved in luteinization and progesteronesecretion which are also induced by LH (see figure 1below). This points out that an increase in plasmaprogesterone concentrations does not necessarily meanthat ovulation has taken place (Poyser, 1992).Source: Poyser (1992).Fig. 1: Pathway in ovulating and progesterone secretions induced by LH.LuteolysisProgesterone which initially is produced in theCorpus luteum is necessary to prepare the uterus forimplantation of a fertilized ovum and to monitor thepregnancy until the placenta can begin progesteroneproduction. Interruption of progesterone production bythe Corpus luteum then leads to termination ofpregnancy. In 1969, it was shown that PGF2σ causedluteolysis in rats and in guinea pigs. The uterus wasshown to be the source of luteolysin identified as PGF2σ(Blatchley, 1969). The luteolytic action of PGF2σ may bedirectly through blood flow away from the Corpus luteum(Clark and Myatt, 2008).Early pregnancyIt is evident that if an animal becomes pregnant,the luteolytic effect of the uterus has to be prevented,since continued progesterone output from the ovary isnecessary for the whole gestation in some species e.g incattle, pig, and goat or the first third of the gestation e.gsheep and guinea pig.In species like sheep and goat, the embryoLHAdenyl cyclase ATPATPCAMPProstaglandinproductionsteroidegenesisovulationProgesteronesecretion28 B. OKON, L. A. IBOM, A. E. BASSEY AND F. I. OKONsecretes a protein called ovine trophoblast protein-1(OTP-1) and caprine trophoblast protein-1 respectivelyand they are synthesized by the embryo from the 12thand 22nd day of pregnancy for the sheep and goat on the15th and 21st day of pregnancy. These proteins inhibitendometrial PGF2σ synthesis (Imakawa et al., 1988 andGnatek et al,. 1989).However in pigs the conceptus does not inhibituterine PGF2σ secretion in-vivo (Harney and Bazer,1989) and also Leckie and Poyser (1990) detected inguinea pig that interferon-σ does not inhibit endometrialPGF2σ synthesis.Interestingly, in those species whose embryossecrete a trophoblast protein-1 are the species in whichovarian oxytocin form part of the physiological stimulusin increasing endometrial PGF2σ synthesis at the end ofthe oestrus cycle. While in pigs, endometrial PGF2σsynthesis is not inhibited during early pregnancy. Thedirection of secretion of PGF2σ produced by the uterusis changed from the uterine venous drainage into theuterine lumen, where the PGF2σ is secreted (Bazer andThatcher, 1977). This means that the Corpora Iutea inthe early pregnant pig is protected from the luteolyticinfluence of PGF2σ.ParturitionParturition occurs not only through withdrawal ofinhibitory factors but also activation of stimulatorysignals or hormones. Glucorcorticoids not only stimulatefetal tissue differentiation and maturation, but in manyspecies they also initiate parturition by acting in a seriesof positive feed toward loops to alter placentalsteroidogenesis (Jenkin and Young, 2004).Glucocorticoids also activate immune and inflammatorypathways, unregulated PGHS-2, attenuate PGDHleading to prostaglandin synthesis and stimulate furtherglucocorticoid production (Whittle et al., 2006). It isclearly recognized in pregnant animals and women thatlabour, is associated with an inflammatory response thatculminates in release of prostaglandin (Christiaens etal., 2008).Placental DeliveryOnce delivery is completed and theallantochorion begins to detach from the uterus,maternal prostaglandin concentrations decline (Haluskaand Currie, 1998). Generally, prostaglandinconcentrations are low within one hour of spontaneousfoaling associated with placentary delivery (Vivrette etal., 1995). In other species, reduced maternalprostaglandin concentrations at birth are associated withretained fetal membranes (Olson, 2003). Thisrelationship was not observed in one study of heavydraught mares (Ishii et al., 2008) but whenprostaglandins were blocked by administration of thePGHS-2 inhibitor, flunixin meglumine, prior to labour,placental delivery was delayed (Vivrette et al., 1995).Prostaglandins and Oestrus synchronizationThree products, lutalyse, estrumate andbovilene, have been approved for use in beef cows andheifers for estrous synchronization. All areprostaglandins and work similar, but differ slightly in theirchemical makeup with different half lives and dosagelevels.When injected at the recommended dosage,these products act by rapidly regressing the Corpusluteum (CL) on the ovaries of cycling females that are indays 6-16 of their estrous cycles. In other words, theinjection decreases the function of the CL; which allowsthese females to return to estrus within 2-5 days andsynchronizing their estrous cycles. Females in days 17-20 will be estrous normally within 1-4 days and will alsobe synchronized. Females in days 1-5 of the cycle andnon-cycling females that do not have a mature CL willnot respond to the injection. Therefore with oneinjection, only about 75 percent of the cows cycling in aherd can be synchronized. If all cycling females are tobe synchronized, two injections are needed (Deutscher,1999).Myometrial activityIt is well documented that PGF2σ and PGE2contract smooth muscles but PGF2σ infused into ratsnear their tail to induce uterine contractions andparturition (Liggius et al., 1972). However, PGF2σadministration to sheep during parturition does not havea stimulant effect on the uterus, so PGs may aid but notinitiate expulsion of the fetus (Mitchell et al., 1976b).CONCLUSIONIn conclusion, prostaglandins are involved inseveral reproductive processes, namely: LH release,ovulation, luteolysis and parturition. Due to theirluteolytic action, PGF2σ or lutalyse can be useful foroestrus synchronization and induced parturition inanimals.REFERENCESBazer, F. W. and Thatcher, W. W., 1977. Theory ofmaterial recognition in swine based on estrogencontrolled endocrine versus exocrine secretionof PGF2σ by uterine endometrium.Prostaglandin, 14:397-402.Blatchley, F.  R., 1969. Luteolytic effects ofprostaglandins in guinea pigs. Nature,221:1065.Carlson, J. C.; Wong. P. and Perrin, D. G., 1977a. Theeffects of prostaglandins and mating on releaseof LH in the female rabbit. Journal ofreproduction and Fertility, 51:87-92.Christiaens, I.; Zanogoza, D. B; Guilbert, L.; Robertson,S. A and Olso, D. M.,  2008. Inflammatory processesin pre-term and term parturition. Journal ofReproduction Immunology, 79:50-57.Clark, K. and Myatt, J. G., 2008. Prostaglandins and thereproductive cycle. Glown, IO: 3843-3849.THE ROLE OF PROSTAGLANDINS IN LIVESTOCK PRODUCTION 29Deutscher, G.  D., 1999. Estrus synchronization of beedcattle. Nebraska Extension Beef CattleReproduction MP, 54:20-23.Down, S. M. and Longe, F. J., 1983. An ultrastructurestudy of pre-ovulatory apical development inmouse ovarian follicles. Effect of Indomethacin.Anatomical Record 205:159-168.Gnatek, G. G.; Smith, L. D.; Duby, R.  T. and Godkin, J.A. 1989. Maternal recognition of pregnancy in goats;effects of conceptus removal on intestineintervals and characterization of conceptusprotein reproduction during early pregnancy.Biology of Reproduction, 41:655-664.Haluska, G.  J. and Currie, W.  B., 1998. Variation inplasma concentrations of oestradiol-17 beta andtheir relationship to those of progesterone, 1314 dihydro-15-keto-prostaglandin F-2 alpha andoxytocin across pregnancy and at perturiion inpony mares. Journal of reproduction andFertility, 84:635-646.Hams, P. G.; Ojeda, S. R. and Mccana, S. M.,  1974.Prostaglandin induces release of pituitarygonadiotropins; central nervous system andpituitary sites of action. Endocrinology 94:1459-1464.Harney, J.  P. and Bazer, F.,  1989. 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The pattern of glucocorticoid andestrogen receptors may explain differences insteroid dependency of intrauterine prostaglandinproduction of parturition in sheep. Journal ofSociety of Gynecology Investigation 13, 506-511.Zanagnole, V.; Dharmarajan, A. M.; Endo, K. andWallace, E. E., 1996. Effects of acetylsalicylic (asprin)and naproxen sodium (norpoxen) on ovulation,prostaglandin and progesterone production inthe rabbit. Fertility of sterilization, 65:1036.30 B. OKON, L. A. IBOM, A. E. BASSEY AND F. I. OKON

The role of prostaglandins in livestock production

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The role of prostaglandins in livestock production

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