L5: The Luteal Phase

Question 1

what phase of estrus is marked by
* low estrogen
* LH surge has just occured
* ovulation occurred recently

Answer 1

metestrus

Question 2

what phase of estrus
* progesterone peaks and is sustained at high levels (ovulation suppressed)
* estradiol is low

Answer 2

diestrus

Question 3

what phase of estrus
* maximum corpus luteum size
* elevated progesterone inhibits final follicular development

Answer 3

diestrus

Question 4

what phase of estrus
* CL regresses (due to release of PGF2alpha) at the end of this phase is there if no pregnancy

Answer 4

Diestrus

Question 5

granulosa cells secrete _______ and _______ to increase blood supply to the new corpus luteum

Answer 5

vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF)

Question 6

what is luteal hormone output dependent on

Answer 6

basal LH levels- maintained by pulses of GnRH

Question 7

how does LH stimulate steroidogenesis

Answer 7

by activating cholesterol desmolase

Question 8

what enzyme is needed for progesterone synthesis in the granulosa cell

Answer 8

3B-Hydroxysteroid dehydrogenase (3B-HSD)

Question 9

Progesterone is released when there is an active…?

Answer 9

corpus luteum

Question 10

what are the effects of progesterone on the hypothalamus

Answer 10

negative feeback - blocks progesterone and estrogen priming

Question 11

what are the effects of progesterone on the endometrium of the uterus

Answer 11

promotes conditions needed for a fertilized egg

Question 12

what produces relaxin in the cow

Answer 12

Corpus luteum
(produced by placenta in other animals)

Question 13

what is the target and function of relaxin

Answer 13

target: uterus, soft CT
function: synergistic effect w/ progesterone to maintain pregnancy

Question 14

T/F: the CL has a limited lifespan

Answer 14

T
pig,horse,primate,cow: 10-14 d
ewe: 17 d
dog: up to 90 days

Question 15

at the end of the luteal phase, CL becomes what

Answer 15

corpus albicans

Question 16

corpus luteum regresses at the end of _______ if there is no pregnancy due to _____ released by uterus

Answer 16

diestrus
PGF2alpha

Question 17

the CL produces oxytocin in what animals

Answer 17

Cow

Question 18

the CL produces estradiol in what animals

Answer 18

primates, pigs, rats

Question 19

during the luteal phase, ______ maintains the corpus luteum

Answer 19

LH (release caused by GnRH pulses)

Question 20

at the end of the ____ phase, _____ terminates the CL and progesterone secretion

Answer 20

luteal
PGF2alpha

Question 21

what animals produce PGF2alpha in the endometrium of their uterus

Answer 21

cow, horse, pig, sheep

Question 22

what is luteolysis

Answer 22

CL regression

Question 23

what stimulates luteolysis

Answer 23

estrogen/progesterone and oxytocin

Question 24

what are the 2 main effects of PGF2alpha

Answer 24

1. opens Ca channels in granulosa cells, induces apoptosis through high intraceullar Ca
2. Activation of PKC which inhibits mitochondrial transport of cholesterol and progesterone synthesis

Question 25

where does the initial signal for oxytocin positive feedback come form

Answer 25

posterior pituitary

Question 26

what signals the release of luteal oxytocin that signals back to the uterus

Answer 26

PGF2alpha

Question 27

what is the role of oxytocin acting through positive feedback on the corpus luteum

Answer 27

oxytocin leads to destruction of CL oxytocin signals uterus to produce PGF2alpha which destroys CL

Question 28

in horses, PGF2alpha is released into the ______ blood from either of the uterine horms

Answer 28

systemic blood

Question 29

what is the vascular pathway for PGF2alpha in cows and sheep?

Answer 29

PGF2alpha is produced in uterus endometrium, **released into ovarian veins **and is **transferred to the ipsilateral ovarian artery through a counter current exchange mechanism**

Question 30

what is the effect of endometritis on the luteal phase in cows

Answer 30

it increases the time of the luteal phase

Question 31

Prolactin (PRL) is secreted from the ______ or the ______ dyring late stage pregnancy in the bitch and rat

Answer 31

anterior pituitary endometrium

Question 32

what is the target of prolactin (PRL) in the rat, bitch and ewe? What is the target in mammals

Answer 32

rat , bitch, ewe: targets the CL all mammals: targets mammary glands

Question 33

what is the effect of prolactin

Answer 33

luteotropic functions, required for initiation and maintenance of milk synthesis

Question 34

what suppresses prolactin

Answer 34

dopamine

Question 35

use of anti prolactin drugs (dopamine agonists or serotonin antagonists) in the bitch will induce _____ in days 4-48 of cycle or induce _______ and cause _______ if given mid pregnancy

Answer 35

estrus if given during days 4-48 if given mid-pregnancy, will induce luteolysis and cause abortion

Question 36

what (and when) stimulates the release of prolactin in the bitch

Answer 36

increasing levels of estrogen during late diestrus

Question 37

what stimulates prolactin release in rodents

Answer 37

copulation