Maternal recognition of Pregnancy Flashcards
What is the early conception factor?
- It is a maternal response within hours of fertilisation.
- Doesn’t count as maternal recognition of pregnancy, just means it knows the fertilised egg is there.
- Present in sheep, cattle, pigs. Protects the embryo by causing the binding of local T-lymphocytes.
Describe the initiation of luteolysis in ruminants
- The appearance of endometrial oxytocin receptors (OXTR)
- The OXTR reappear before P4 falls (they are suppressed by P4), oxytocin from the CL binds to OXTR.
- Stimulated PGF2a to be released.
- OXTR are likely to be involved in mares/ pigs too
What does the binding of oxytocin to OXTR stimulate?
PGF2a pulsatile release
- this is excreted from endometrium
- PgF2a is delivered to ovary b y the counter current system allowing it to have a direct effect on ovary.
Describe the positive feedback loop of Oxytocin on PGF2a
-Oxytocin acts on endometrium of uterus causing a pulse of PGF2a which acts on the CL
Define maternal recognition of pregnancy
- Adaptation of the maternal endocrine system to the presence of the conceptus.
- Aim is to maintain the CL and P4 production.
- It is an embryonic signal that happens before luteolysis and it NOT conscious
Describe the effect of progesterone on maintaining pregnancy
- Maintains uterine gland secretory function: makes glands more coiled and branched. Increases the concentration of iron in the histotroph to help support embryo
- Suppresses myometrial contractions and luteolytic mechanism
- Suppresses FSH/ LH secretion to reduce follicular development
What is interferon tau and which species is in involved in?
- Ruminants
- Inteferon tau (TFNT) is a protein found in the blastocyst.
- Begins to be expressed when embryo starts to elongate (day 16)
- Stimulated by uterine growth factors (IGF1/ IGF2)
- Production of INFT is related to embryo size (bigger embryo= more INFT produced)
How does INFT relate to embryo mortality?
-Smaller/ less well developed embryos secrete less IFNT which prevents them being able to prevent luteolysis which leads to embryo mortality.
Describe the actions of INFT
-Acts on the endometrium: suppresses OXTR expression, stimulates protein synthesis critical for embryo and has antiviral activity.
Describe the maternal recognition signal
- Prevents up regulation of oxytocin receptor
- Suppresses PGF2a pulsatile secretion
- Maintains P4 (indirectly)
What affect does administering exogenous INFT have?
Prolongs luteal phase- keeps P4 higher for longer
Describe the effects of oestradiol of pregnancy in pigs
- Allows the blastocyst to elongate very fast.
- Secreted just before implantation, redirects flow of PGF2a away from uterine vein
- Redirection results in: in NON PREGNANT sows the lumen epithelial cells produce PGF2a which is then sent from uterine vein to the ovary to cause luteolysis.
- In PREGNANT SOWS the blastocyst produced oestradiol so the PGF2a is released into the lumen where the embryo is free living, the embryo metabolises and inactivates it so it cannot reach the CL this preventing luteolysis.
Describe the maternal recognition of pregnancy in horses
- Oxytocin stimulates luteolytic PGF2a
- Embryo suppresses OXTR but there is no blastocyst interferon
- The blastocyst signal is unknown
- eCG is NOT the MAP signal
In which species does the embryo elongate?
- Cow and pig
- Remains spherical in the horse
Describe early migration of the embryo in the horse
In the horse the uterus has high tone whereas in most species it has a flaccid tone.
The embryo remains spherical and unattached, constantly migrating throughout early pregnancy- this is crucial for MRP.
