The primary function of the corpus luteum is secretion of the hormone progesterone, which is required for maintenance of normal pregnancy in mammals. The corpus luteum develops from residual follic...

https://www.physiology.org/doi/pdf/10.1152/physrev.2000.80.1.1

Mechanisms Controlling the Function and Life Span of the Corpus Luteum

In many nonprimate mammalian species, cyclical regression of the corpus luteum (luteolysis) is caused by the episodic pulsatile secretion of uterine PGF2α, which acts either locally on the corpus l...

Luteolysis: A Neuroendocrine-Mediated Event

Publisher Summary This chapter presents an overview of the regulation of the mammalian corpus luteum (CL) The CL is an ovarian follicle in which the rapid regression—that is otherwise the fate of all postovulatory follicles—is temporarily arrested In the mammalian CL, progesterone secretion goes hand in hand with the postponement of regression It is fairly certain that reptilian CL also secretes progesterone The mammalian CL is formed during the period around ovulation by a transformation of the cells lining the cavity of the follicle Luteinization affects the granulosa cells in all species It involves an enormous enlargement of the cell with a great increase in the nucleus–cytoplasm ratio and the formation of a very distinct cell wall, the development of an extensive capillary network enmeshing all the cells, a marked proliferation of the endoplasmic reticulum, and its transformation from a predominantly rough to a predominantly smooth type, a marked proliferation of the mitochondria from a small round or rod shape type with lamelliform cristae into larger and more varied shapes with tubular and villiform cristae, and an increase in the complexity of the Golgi apparatus The CLs activity differs most from that of the follicle in how much rather than in what kinds of steroid it makes The principal change is a striking increase in progesterone secretion, accompanied by a variable, but severe fall or even loss of the capacity for estrogen and androgen secretion

The Regulation of the Mammalian Corpus Luteum

I. Introduction ABOUT 5 yr ago it was discovered that a protein which was secreted in quantity by preimplantation sheep conceptuses and implicated in preventing luteolysis during the second and third weeks of pregnancy was, in fact, structurally related to type I interferons (IFN), proteins best known for their antiviral and immunomodulatory activities. This discovery attracted considerable attention because it revealed a new and completely unsuspected role for a cytokine as a reproductive hormone. Several reviews have been published on various aspects of this topic (1–10). In the more comprehensive updated article that follows, we describe how IFN came to be implicated as antiluteolytic agents in domestic ruminant species, the properties of these IFN, and some of the unusual features pertaining to their expression and transcriptional regulation. We address the questions as to whether these IFN have any unique biological and structural properties, as to how they evolved, and as to whether type I IFN in ge...

/pdf/interferons-as-hormones-of-pregnancy-1gyi7sz1ib.pdf

Interferons as hormones of pregnancy.

In recent years, considerable progress has been made in our understanding of the endocrine mechanisms that control the pattern and timing of uterine secretion of prostaglandin F2 alpha (PGF2 alpha) during luteolysis in ruminants. Oxytocin may be important in establishing a pulsatile pattern of secretion. Neurohypophyseal oxytocin appears to be released in a pulsatile fashion and may initiate each episode of PGF2 alpha secretion from the uterus. Uterine PGF2 alpha stimulates release of oxytocin from the corpus luteum. Luteal oxytocin further stimulates secretion of PGF2 alpha from the uterus and may induce a transient refractoriness of the uterus to subsequent stimulation with oxytocin. Uterine refractoriness subsides after approximately 6 h. A similar desensitization phenomenon occurs in response to PGF2 alpha at the level of the corpus luteum. Together, uterine and luteal refractoriness may account for the interval between pulses of PGF2 alpha observed during luteolysis. Uterine secretory responsiveness to oxytocin increases at luteolysis, when endogenous, pulsatile secretion of PGF2 alpha normally begins. Thus, the acquisition by the uterus of responsiveness to oxytocin may determine when endogenous secretion of PGF2 alpha occurs during the estrous cycle. Uterine secretory responsiveness to oxytocin develops slowly, in the presence of progesterone. Progesterone exerts two types of effects that contribute to the regulation of PGF2 alpha secretion. First, prolonged exposure to progesterone appears to promote uterine accumulation of arachidonic acid, prostaglandin endoperoxide synthase, and other substances needed for synthesis of PGF2 alpha. Second, progesterone exerts a suppressive effect on secretion, which wanes after prolonged exposure. Together, these effects of progesterone ensure that PGF2 alpha is secreted only at the appropriate time to induce luteolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Hormonal regulation of uterine secretion of prostaglandin F2 alpha during luteolysis in ruminants.

Hormonal changes around bovine luteolysis.

Jugular levels of 13, 14-dihydro-15-keto-prostaglandin F and progesterone around luteolysis and early pregnancy in the ewe.

Temporal relationship between plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F and neurophysin I/II around luteolysis in sheep

Progesterone and oestradiol concentrations in the peripheral plasma of 12 dairy cows during the oestrous cycle were determined by competitive protein-binding and radioimmunoassay respectively. The levels of progesterone reached a peak of 6-7 ng/ml in mid-cycle, then began to fall 4 days before oestrus to values of about 1 ng/ml at oestrus and remained low for a further 4 days. Peak levels of oestradiol (11.2 ± 1.3 pg/ml, s.e.) occurred on the day before oestrus and a second peak (7.9 ± 2.9 pg/ml) occurred on Days 6-8 of the cycle.

https://www.tandfonline.com/doi/pdf/10.1080/00288233.1975.10421012

Plasma hormone levels in the cow

Summary. Three cows and 2 sheep were passively immunized against prostaglandin (PG) F on Day 16 and Days 13\p=n-\15of the oestrous cycle respectively. The PGF antiplasma was raised in ovariectomized ewes against a PGF-2\g=a\\p=n-\bovineserum albumin complex and showed 100%, 12\m=.\5%,0\m=.\3%,<0\m=.\05%and <0\m=.\01% cross-reactivity with PGF-2\g=a\,PGE-2, PGA-2, PGB-2 and arachidonic acid, respectively. Control animals were given an equivalent amount of ovariectomized ewe plasma. In all passively immunized animals there was evidence of a persistent corpus luteum as indicated by plasma progesterone concentrations and the failure of the animals to return to oestrus until at least 29 days after treatment. These data are consistent with previous proposals that PGF-2\g=a\ is the uterine luteolytic factor in sheep and cattle.

/pdf/prolongation-of-the-oestrous-cycle-in-cows-and-ewes-after-2jw7cqlos2.pdf

R. J. Fairclough

Papers

Hormonal changes around bovine luteolysis.

Jugular levels of 13, 14-dihydro-15-keto-prostaglandin F and progesterone around luteolysis and early pregnancy in the ewe.

Temporal relationship between plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F and neurophysin I/II around luteolysis in sheep

Plasma hormone levels in the cow

Prolongation of the oestrous cycle in cows and ewes after passive immunization with PGF antibodies.