Effects of Intrafollicular Injections of Prostaglandins in Non-Pregnant and Pregnant Ewes

Inskeep, E. K.; Smutny, W. J.; Butcher, R. L.; Pexton, J.E.

doi:10.2527/jas1975.4141098x

Cited by 57 publications

(13 citation statements)

References 9 publications

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“…In ruminants, the CL of early pregnancy is more resistant to the luteolytic action of PGF 2a [17][18][19][20][21] on , and the resistance is even greater when multiple embryos are present [18]. Injection of PGF 2a into an ovarian artery or follicles of early pregnant sheep caused luteolysis in 28% and 17% of animals, compared with 78% and 83% in nonpregnant sheep, respectively [17,19].…”

Section: Introductionmentioning

confidence: 88%

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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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Section: Introductionmentioning

confidence: 88%

“…Injection of PGF 2a into an ovarian artery or follicles of early pregnant sheep caused luteolysis in 28% and 17% of animals, compared with 78% and 83% in nonpregnant sheep, respectively [17,19]. Exogenous estradiol at doses causing premature luteolysis in cyclic sheep is less effective in pregnant sheep [22].…”

Section: Introductionmentioning

confidence: 89%

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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“…The factor from the pregnant uterus may be PGE 2 , since this hormone inhibits the PGF2a-induced decrease in progesterone synthesis and since treatments with PGE 2 appear to lengthen the life span of the CL in sheep [125], cattle [126], and primates [127]. However, definitive studies on the role of PGE 2 in maternal recognition of pregnancy have not yet been performed.…”

Section: Early Pregnancymentioning

confidence: 94%

Luteal Function: The Estrous Cycle and Early Pregnancy

Niswender

Juengel

McGuire

et al. 1994

Biology of Reproduction

151

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A number of morphological and biochemical changes occur as the cells of the recently ovulated follicle luteinize and develop into a functional CL. There are two distinct steroidogenic luteal cell types that appear to differentiate from thecal and granulosal cells in the follicle. The control of progesterone secretion is quite different in the two cell types. Prostaglandin F2 alpha (PGF2 alpha) is the primary luteolytic hormone in most mammals. PGF2 alpha appears to exert its antisteroidogenic actions via activation of the protein kinase C system, while its cytotoxic effects appear to be mediated via a dramatic increase in intracellular levels of free calcium. The mechanisms involved in maternal recognition of pregnancy are very diverse between species and may involve direct luteotropic stimulation of the CL, reduced uterine secretion of PGF2 alpha, and/or inhibition of actions of PGF2 alpha at the level of the CL.

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“…Those studies were interpreted to indicate that the conceptus does not have a systemic effect on the CL. However, the CL of pregnancy is much more resistant to lytic effects of PGF2α (Inskeep et al 1975 ;Mapletoft et al 1976a ;Pratt et al 1977 ;Silvia and Niswender 1984 ). Thus, the elongating conceptus could have endocrine effects on the CL during early pregnancy in sheep.…”

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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Effects of Intrafollicular Injections of Prostaglandins in Non-Pregnant and Pregnant Ewes

Cited by 57 publications

References 9 publications

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

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

Luteal Function: The Estrous Cycle and Early Pregnancy

Implantation and Establishment of Pregnancy in Ruminants

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