Lecture 11: The Luteal Phase of the Estrous and Menstrual Cycle Animal Science 434 Lecture 11: The Luteal Phase of the Estrous and Menstrual Cycle

Ovulation Ovulation Luteal Phase Follicular Phase P4 Production CL Formation (Metestrus) Follicular Phase Relative Progesterone Levels (Blood) P4 Production (Diestrus) Luteolysis

steroid synthesis progesterone collagenase theca interna

present 1-3 days following ovulation blood vessels in follicle wall rupture walls collapse cells intermix old basement membrane becomes connective tissue of CL

increases in size papilla forms composed of cells from the granulosa and theca interna progesterone production increases a small cavity may be present where the folliclular antrum was present

Luteal Tissue Large cells from granulosa Small cells from the theca interna

Mitochondria Secretory Granules - Oxytocin - Relaxin

Functional Capability of CL the number of luteal cells large cells undergo hypertrophy (3 fold) small cells undergo hyperplasia (5 fold) vascularization of CL Initiated by angiogenic factors from follicle Vascularity effects CL steroid synthesis and delivery of hormones Insufficient CL function Failure to maintain pregnancy Important in domestic animals

Progesterone Targets Blocks Estrus Negative Feedback Aveolar Development

Molecular Mechanism of LH on Luteal Cell (cAMP second messenger) Progesterone LH G Receptor Plasma Membrane Adenylate Cyclase cAMP PKA ATP cAMP R S-ER Steroid Synthesis C (+ PO4) Mitochondria Pregnenolone Cholesterol Nucleus DNA Histones Cholesterol mRNA R-ER Protein Synthesis Protein Synthesis (Enzymes)

Molecular Mechanism of LH on Luteal Cell (cAMP second messenger) Chol LDL Progesterone LH G Receptor Plasma Membrane Adenylate Cyclase cAMP Chol LDL PKA ATP cAMP R S-ER Steroid Synthesis C Chol-Ester (+ PO4) LDL Mitochondria Chol Esterase Pregnenolone Cholesterol Cholesterol R-ER Protein Synthesis Protein Synthesis (Enzymes)

Luteolysis Uterus PGF2a Oxytocin

Luteolysis in Cows, Ewes, Sows Normal Uterus Total Hysterectomy CL CL Lifespan Longer CL Normal Lifespan Similar to Gestation Length Contralateral Hysterectomy Ipsilateral Hysterectomy CL Lifespan Longer CL Normal Lifespan >35 days

Luteolysis Uterus PGF2a Oxytocin

Prostaglandin F2a Control of Luteolysis Uterine Horn Progesterone from CL stimulates production of uterine PGF2a after day 15 in cow Prostaglandin synthesis by uterine endometrium is released into the uterine vein. Corpus Luteum Oviduct Ovary Uterine Vein Ovarian Pedicle PGF PGF2a is picked up by ovarian artery through counter current exchange and delivered back to the ovary where it causes lysis of the CL PGF into Artery Uterine Artery

Contralateral Hysterectomy Ipsilateral Hysterectomy Normal Uterus Total Hysterectomy CL CL Normal Lifespan CL Maintained Luteolysis Mare Contralateral Hysterectomy Ipsilateral Hysterectomy 50% of CL’s Maintained 50% of CL’s Maintained

Blood Supply to Uterus and Ovary in the Mare

PGF Not Effective (Sow) PGF Not Effective (Cow, Ewe, Mare)

Luteolysis Uterus PGF2a Oxytocin

Relationship of Oxytocin and PGF2a Posterior Pituitary Anterior Pituitary Oxytocin CL PGF2a Ovary Uterus

Luteolysis decreased blood flow cellular response Immune response apoptosis progesterone synthesis Immune response Lymphocytes Macrophages

Molecular Mechanism of PGF (Ca2+ Second Messenger) G-protein Plasma Membrane Receptor PIP2 PIP2 DAG IP3 PLC Protein Kinase C R R Ca2+ Cholesterol Ca2+ Endoplasmic Reticulum Apoptosis Progesterone Plasma Membrane

Luteolysis decreased blood flow cellular response Immune response apoptosis progesterone synthesis Immune response Lymphocytes Macrophages

Menstrual Cycle

Anterior Pituitary Hormones LH FSH Progesterone Ovarian Hormones Estradiol Ovulation Corpus Albicans Follicle Corpus Luteum Ovary Recruitment Recruitment Dominance Selection Uterine Endo- metrium 2 4 6 8 10 12 14 16 18 20 22 24 26 28 2

Luteolysis in the Primate Does not require the uterus CL lifespan in the human is 12-14 days unless pregnancy occurs In the absence of pregnancy, CL self destructs Possible intra-ovarian oxytocin receptors and PGF2a production Menstruation Drop in P4 and E2 Endometrial PGF2a, vasoconstriction, necrosis Endometrial inflammation and tissue degeneration

Manipulating Ovulation Hormonal induction of ovulation PGF2a GnRH Progestins Superovulation FSH eCG

Principle of PGF2a Use Regress active corpus luteum Only effective on a day 5 - 17 CL Not effective on days: 1 - 4 (CL not responsive) 18 - 21 (CL already regressed)

Induction of Ovulation with PGF2a Progesterone Dominance Recruitment Selection Ovulation Follicular Size Ovulation 9 16 21 Day After Ovulation

Induction of Ovulation with PGF2a Progesterone Follicular Size Ovulation 9 16 21 Day After Ovulation

Induction of Ovulation with PGF2a Progesterone Follicular Size PGF2 Ovulation 9 16 21 Day After Ovulation

Induction of Ovulation with PGF2a Progesterone Follicular Size PGF2 Ovulation 9 16 21 Day After Ovulation

Eliminate current follicular wave Ovsynch GnRH PGF2 GnRH 8 - 18 hours Timed AI 7 Days 36 - 48 hours Eliminate current follicular wave Luteolysis Ovulates dominant follicle

Induction of Ovulation with PGF2a Progesterone Dominance Recruitment Selection Ovulation Follicular Size Ovulation 9 16 21 Day After Ovulation

Induction of Ovulation with PGF2a Progesterone Follicular Size GnRH Ovulation 9 16 21 Day After Ovulation

Induction of Ovulation with PGF2a Progesterone Follicular Size GnRH Ovulation 9 16 21 Day After Ovulation

Induction of Ovulation with PGF2a Progesterone PGF2a Follicular Size GnRH Ovulation 9 16 21 Day After Ovulation

Induction of Ovulation with PGF2a AI Progesterone PGF2a Follicular Size GnRH GnRH Ovulation 9 16 21 Day After Ovulation

Eliminate current follicular wave Ovsynch GnRH PGF2 GnRH 8 - 18 hours Timed AI 7 Days 36 - 48 hours Eliminate current follicular wave Luteolysis Ovulates dominant follicle

Use of Progestogens Principle: Maintain the cow under the influence of progesterone until corpus luteum regresses, remove progesterone - animal respond to progesterone with estrus and ovulation 2-5 days later. Administration: Injection Feed Implant Pessary or Control Internal Drug Release (CIDR) This does not regress the CL!!!!

Progestens Effect on Ovulation Progesterone From C.L. Ovulation Ovulation Estrus Estrus 17 21 Follicular Wave Follicular Wave Follicular Wave

Progestens Effect on Ovulation Progesterone From C.L. Ovulation Ovulation Estrus Estrus Ov. 17 21 Follicular Wave Follicular Wave Follicular Wave Remove CIDR P4 from CIDR P4 from CL Estrus Estrus 17 21 Follicular Wave Follicular Wave Follicular Wave

Stimulating Follicular Development eCG or FSH Multiple Ovulations Ovulation Estrus Estrus Progesterone From C.L. PGF2a 17 eCG or FSH Estrus Estrus First Follicular Wave 10-12