PP20 Maternal Recognition of Pregnancy Chapter 13 pg 291296

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PP20Maternal Recognition of PregnancyChapter
13 pg 291-296
ANS 3319Dr. Michael J. FieldsUniversity of
Florida
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Mechanisms to Rescue the CL

• I. Conceptus secretes a product to stimulate
  CL function
• Human
• Trophoblast secretes hCG ( day 10).
• Luteotrophic
• Sheep and Cow
• Trophoblast secretes PGE2 ( day 6).
• Luteoprotective

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Mechanisms to Rescue CL

• II. Conceptus secretes a product that blocks
  PGF2a secretion from uterus
• Sheep and Cow
• Secretes Interferon Tau (IFt).
• IFt blocks uterine pulses of PGF2 a.
• Blocks OT Receptor synthesis by interfering with
  arachidonic acid cascade.
• Blocks COX-2.
• Blocks Phosphotidylinositol (PI) messengers.

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CL Regression of Estrous Cycle
CL
CL Regression
Oxytocin
PGF2?
PGF2?
Uterus
Arachidonic Acid
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Early Pregnancy
Ovulation
Ovary
Oxytocin
Prostaglandin
Uterus
Interferon tau
Embryo
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Oxytocin Induction PGF2a Synthesis
Phospholipase A2
Arachidonic Acid
Cox-2
PGH2
PGE-S
PGF-S
OT
OTR
IP-DG
PGE2
PGF2a
PG Reductase
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Mechanisms to Rescue the CL

• II. Conceptus secretes a product that blocks
  PGF2a secretion from uterus
• Horse
• Conceptus secretes an unidentified product MW lt
  6000.
• EPSI - Endometrial Prostaglandin Synthesis
  Inhibitor.
• Ex Cytosolic Linoleic Acid
• Uncouples arachidonic acid cascade and OT release
• Decrease in OT-Receptor number or affinity

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Mechanisms to Rescue the CL

• III. Conceptus secretes a product that gives
  resistance to PGF2a
• Sheep Pig
• CL becomes resistant to PGF2a.
• In sheep, CL resistant to lethal effect of
  PGF2a on day 13 16 other days on either side,
  CL is sensitive to PGF2a.

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Mechanisms to Rescue the CL

• IV. Conceptus secretes a product that
  redirects PGF2a secretion from blood into uterine
  lumen
• Pig
• Trophoblast secretes Estradiol-17ß starting day
  11.
• Switches the secretion of PGF2a from endocrine to
  exocrine.
• From circulatory system to uterine lumen
• PGF2a is sequestered in lumen

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Mechanisms to Rescue the CL
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Migration of Conceptus

• Horse
• Conceptus migrates around uterus to inhibit
  secretion of PGF2a.
• Must make contact with entire surface area of
  endometrium
• Movement measured in mm/hr.
• Day 16 movement stops.
• Cow, Ewe Sow
• Conceptus rapidly elongates.
• Membranes fill both uterine horns.

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Migration of ConceptusSow

• Embryos migrate through both horns from day 8 to
  12.
• Embryos must be in both horns by day 12 then
  elongation occurs.

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Local Counter Current Transfer of PGF2a
Cow, Ewe Sow

• Conceptus must be in uterine horn that is on the
  same side (ipsilateral) as the CL.
• PGF2a degraded rapidly in circulation by lungs.

• 65 degraded in one pass takes 30 sec.
• Local Counter Current Transfer of PGF2a

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Local Counter Current Transfer of PGF2a
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Local Counter Current Transfer of PGF2a
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Local Counter Current Transfer of PGF2a
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AlternativeMechanisms for CL Rescue

• Horse
• Has systemic circulation of PGF2a with very slow
  metabolism.
• Very sensitive to PGF2a.
• Other Species
• CL is maintained equal to lifespan of pregnancy,
  whether pregnant or not.
• Examples marsupials dogs.