The Ovarian Artery as the Final Component of the Local Luteotropic Pathway Between a Gravid Uterine Horn and Ovary in Ewes

Mapletoft, R.J.; Lapin, D.; Ginther, O.J.

doi:10.1095/biolreprod15.3.414

Cited by 69 publications

(24 citation statements)

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“…This demonstrated that the pregnancy signal was local and not systemic and was carried in the local uterine vein. Similarly, anastomoses of the ovarian artery from the gravid side to the non-gravid side resulted in CL maintenance Mapletoft et al, 1976c) demonstrating that the signal passed from the uterine vein to the ovarian artery, only on the same side and not the opposite side from the pregnancy. Thus, it is clear that even though some pregnancy signals may escape the uterus, the critical pregnancy signal that protects the CL in ruminants during early pregnancy is acting locally by passing from the uterine vein to the ovarian artery and not through the systemic circulation.…”

Section: Period II Blockade Of Luteolysis In Early Pregnancyday 18-2mentioning

confidence: 98%

Maintenance or regression of the corpus luteum during multiple decisive periods of bovinepregnancy

Wiltbank¹,

Meidan²,

Ochoa³

et al. 2016

Anim Reprod

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In ruminants, there are specific times during the estrous cycle or pregnancy when the corpus luteum (CL) may undergo regression. This review has attempted to summarize the physiological and cellular mechanisms involved in CL regression or maintenance during four distinct periods. The first period is near day 7 when animals that are ovulating after a period of low circulating progesterone (P4), such as first pubertal ovulation or first postpartum ovulation, are at risk of having a premature increase in Prostaglandin F2α (PGF) secreted from the uterus resulting in early CL regression and a short estrous cycle. The second period is when normal luteolysis occurs at day 18-25 of the cycle or when the CL is rescued by interferon-tau secreted by the elongating embryo. The uterine mechanisms that determine the timing of this luteolysis or the prevention of luteolysis have been generally defined. Induction and activation of endometrial E2 receptors result in induction of endometrial oxytocin receptors that can now be activated by normal pulses of oxytocin. Of particular importance is the observation that the primary mechanisms are only activated through local (ipsilateral) and not a systemic route due to transfer of PGF from the uterine vein to the ovarian artery. In addition at the CL level, studies are providing definition to the cellular and molecular mechanisms that are activated in response to uterine PGF pulses or pregnancy. The third period that is discussed occurs in the second month of pregnancy (day 28-60) when undefined mechanisms result in CL maintenance of an ipsilateral CL but regression of a contralateral (opposite side from pregnancy) CL. The final period that is discussed is regression of the CL just prior to parturition. Although, cortisol from the fetus appears to be the primary initiator of luteolysis, PGF seems to be the final signal that causes regression of the CL. Thus, in all four periods, regression of the CL is likely to be caused by the direct actions of PGF that is secreted from the uterus. The uterine mechanisms that result in secretion of PGF seem to be normally inhibited during the early luteal phase, making short luteal phases not a normal event, and are altered during early pregnancy (day 18-25) resulting in prevention of luteolysis. During much of pregnancy, the mechanisms that cause PGF secretion from the uterus in response to oxytocin are intact but luteolysis does not normally occur, perhaps due to lack of efficient utero-ovarian transfer of PGF.

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Section: Period II Blockade Of Luteolysis In Early Pregnancyday 18-2mentioning

confidence: 98%

Maintenance or regression of the corpus luteum during multiple decisive periods of bovinepregnancy

Wiltbank¹,

Meidan²,

Ochoa³

et al. 2016

Anim Reprod

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“…Moor and Rowson (Moor and Rowson 1966a ) and Mapletoft and coworkers (Mapletoft et al 1976b ) described a local effect of the conceptus in maintaining the ipsilateral but not contralateral CL in ruminants. Those studies were interpreted to indicate that the conceptus does not have a systemic effect on the CL.…”

Section: Regulation Of CL Function By Ifntmentioning

confidence: 99%

Implantation and Establishment of Pregnancy in Ruminants

Spencer

Hansen

2015

Advances in Anatomy, Embryology and Cell Biology

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The establishment of pregnancy in ruminants occurs during the peri-implantation period and involves the suppression of the endometrial luteolytic mechanism to maintain progesterone production by the corpus luteum (CL). Reciprocal interactions between the elongating conceptus (embryo/fetus and associated extraembryonic membranes) and endometrium culminate in implantation. Antiluteolytic effects of the conceptus are due to the production of interferon tau (IFNT) by the trophoblast that has a paracrine effect to inhibit the upregulation of oxytocin receptors in the endometrial epithelia, thereby disrupting uterine release of luteolytic prostaglandin F2 alpha (PGF) pulses. Additionally, IFNT is released into the uterine vein and has endocrine actions to induce ISGs in peripheral tissues. For example, IFNT may induce luteal resistance to PGF, thereby ensuring survival of the CL and maintenance of pregnancy. Survival of the blastocyst and elongation of the conceptus requires embryotrophic factors from the epithelia of the uterus, and those embryotrophic factors are regulated by ovarian progesterone as well as conceptus-derived factors including IFNT and prostaglandins. This review provides new concepts on mechanisms of the establishment of pregnancy and implantation in ruminants with emphasis on conceptus-maternal signaling associated with elongation of the blastocyst and endometrial responses to the presence of a conceptus.

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“…Infusions of IFNT directly into the uterine vein maintained a functional CL in 80% of sheep for up to 32 days through as-yet-unidentified mechanisms [33,34]. Experiments involving anastomosis of the uterine vein or the ovarian artery (OA) from the pregnant to the nonpregnant uterine horn indicated that both luteolytic and luteoprotective mediators need to be transported locally from the utero-ovarian vein (UOV) to the OA via the utero-ovarian plexus (UOP) in sheep and cattle [35][36][37]. Moreover, embryo/ conceptus transfer and hysterectomy experiments indicated that the luteolytic and luteoprotective mechanisms are locally mediated between the uterus and the CL of the ipsilateral ovary and do not act systemically in sheep [38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Intraluteal Prostaglandin Biosynthesis and Signaling Are Selectively Directed Towards PGF2alpha During Luteolysis but Towards PGE2 During the Establishment of Pregnancy in Sheep1

Lee

McCracken

Stanley

et al. 2012

Biology of Reproduction

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In ruminants, endometrial prostalgandin (PG) F(2alpha) causes functional luteolysis, whereas luteal synthesis of PGF(2alpha) is required for structural luteolysis. PGE(2) is considered to be a luteoprotective mediator. Molecular aspects of luteal PGF(2alpha) and PGE(2) biosynthesis and signaling during the estrous cycle and establishment of pregnancy are largely unknown. The objectives of the present study were 1) to determine the regulation of proteins involved in PGF(2alpha) and PGE(2) biosynthesis, catabolism, transport and signaling in the corpus luteum (CL); 2) to investigate the transport of interferon tau (IFNT), PGF(2alpha), and PGE(2) from the uterus to the ovary through the vascular utero-ovarian plexus (UOP); and 3) to compare the intraluteal production of PGF(2alpha) and PGE(2) on Days 12, 14, and 16 of the estrous cycle and pregnancy in sheep. Our results indicate that luteal PG biosynthesis is selectively directed towards PGF(2alpha) at the time of luteolysis and towards PGE(2) during the establishment of pregnancy. Moreover, the ability of the CL of early pregnancy to resist luteolysis is due to increased intraluteal biosynthesis of PGE(2) and PGE(2) receptor (PTGER) 2 (also known as EP2)- and PTGER4 (also known as EP4)-mediated signaling. We also found that IFNT protein is not transported through the UOP from the uterus to the ovary; in contrast, a large proportion of endometrial PGE(2) is transported from the uterus to the ovary through the UOP. These results indicate that endometrial PGE(2) stimulated by pregnancy is transported locally to the ovary, which increases luteal PGE(2) biosynthesis and hence activates luteal PTGER2 and PTGER4 signaling, thus protecting the CL during the establishment of pregnancy in sheep.

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The Ovarian Artery as the Final Component of the Local Luteotropic Pathway Between a Gravid Uterine Horn and Ovary in Ewes

Cited by 69 publications

References 0 publications

Maintenance or regression of the corpus luteum during multiple decisive periods of bovinepregnancy

Maintenance or regression of the corpus luteum during multiple decisive periods of bovinepregnancy

Implantation and Establishment of Pregnancy in Ruminants

Intraluteal Prostaglandin Biosynthesis and Signaling Are Selectively Directed Towards PGF2alpha During Luteolysis but Towards PGE2 During the Establishment of Pregnancy in Sheep1

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