Abstract
Plasma concentrations of oestradiol-17ß, progesterone, 15-keto–dihydro–PGF2α and luteinizing hormone (LH) were monitored in llamas and alpacas after mating with an intact male. Concentrations of LH and PGF2α metabolite were high immediately after copulation. Ovulation occurred in 92% of the animals. The first significant increases in progesterone were recorded on day 4 after mating. In non-pregnant animals the lifespan of the corpus luteum was estimated to be 8–9 days. Luteolysis occurred in association with the release of PGF2α. In pregnant animals, a transient decrease in progesterone concentrations was observed between days 8 and 18 in both species. No significant changes in PGF2α secretion were registered during this period. Oes– tradiol–17ß concentrations were high on the day of mating, declined to low values on day 4, and started to increase again on day 8. Peak values after luteolysis in non-pregnant animals were significantly higher than those registered in pregnant ones. Furthermore, concentrations of oestradiol-17ß were elevated for a longer period in non–pregnant than in pregnant animals. The results suggest that progesterone from the corpus luteum exerts a negative influence on follicular activity in pregnant animals by reducing oes– tradiol-17ß secretion.
Keywords: oestradiol-17ß, Prostaglandin F2α, early pregnancy
Sammanfattning
Plasma koncentrationerna av östradiol-17ß, progesteron, 15-keto-dihydro-PGF2α och luteiniserande hormon (LH) analyserades hos lamor (13) och alpackor (12) efter betäckning. Koncentrationena av LH och PGF2ametaboliten var höga omedelbart efter betäckning. Ägglossning skedde i 92% av fallen. Den första signifikanta ökningen av progesteron kunde registreras 4 dagar efter betäckning. Hos de djur som inte blev dräktiga gick gulkroppen i regression efter 8–9 dagar, vilket sammanföll med en hög sekretion av prostaglandin. Hos de djur som blev dräktiga registrerades en Övergående sänkning i progesteronnivån mellan dag 8 till 18 hos båda djurslagen som inte kunde relateras till en ökad prostaglandin frisättning. Nivån av östradiol-17ß var hög på betäckningsdagen, sjönk till låga värden dag 4 och ökade sedan på dag 8 hos såväl dräktiga som icke dräktiga djur. De högsta nivåerna registrerades hos icke dräktiga djur efter det att gulkroppen hade försvunnit. Nivåerna var också höga under en längre tid hos icke dräktiga djur. Resultaten tyder på att progesteron från gulkroppen undertrycker follikelutvccklingen hos dräktiga djur vilket avspeglar sig i låga mätbara östradiol-17ß nivåer i blod.
Full Text
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Acknowledgments
We thank Dr. J. Roser and Dr. H. Papkoff for supplying the LH antiserum and the equine LH standard. The Swedish Agency for Research in Developing Countries (SAREC), Swedish International Development Agency (SIDA) and Department of Physiopa–thology, Faculty of Veterinary Sciences, UNCPBA, Tandil, Argentina, are acknowledged for financial support.
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