Luteinization And Luteolysis

Question 1

What are the 3 main luteal phase events?

Answer 1

1. Luteinization of follicular cells to luteal cells (granulosa cells to LLC and theca cells to SLC)
2. Growth and development of CL which produces progesterone
3. Luteolysis

Question 2

Effects of progesterone?

Answer 2

-Negative feedback on hypothalamus and anterior pituitary inhibits GnRH and LH surge which prevents estrus
-stimulates uterine glands- histotroph (uterine milk)
-reduces myometrial tone (except in mare)
-final alveolar development in uterine glands

Question 3

Origin of PGF2-alpha

Answer 3

Uterine endometrium (not dogs)

Question 4

Effects of PGF2-alpha

Answer 4

-cessation of progesterone secretion
-structural regression, form corpus albicans
-removes negative feedback on GnRH, causes new follicular phase

Question 5

How does luteolysis occur (PGF2-alpha reach CL) in ruminants?

Answer 5

Countercurrent exchange of PGF2a from ipsilateral uterine vein and ovarian artery. (High 1st pass dilution rate)

PGF2a from uterine endometrium enters uterine v. and moves to ovarian a. Which carries PGF2a to CL causing luteolysis

Question 6

How does luteolysis occur (PGF2-alpha reach CL) in mares?

Answer 6

PGF2a enters systemic system because mare CL is more sensitive to PGF2a. (Low 1st pass dilution rate)

Question 7

How does luteolysis occur (PGF2-alpha reach CL) in sows?

Answer 7

Combination of local and systemic routes:
-medium 1st pass dilution rate (~40%)
-lots of oxytocin in CL
-oxytocin causes uterus to release PGF2a which positively feeds back to stimulate pulse of PGF2a (NSAIDs can block pulsatile release and block luteolysis)
-not responsive to PGF2a until 12-14 days post ovulation