Establishment of pregnancy in sheep and pigs

Fw, Bazer

doi:10.1071/rd9890237

Cited by 74 publications

(25 citation statements)

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“…The transition from endocrine to exocrine secretion occurs between Days 10 and 12 of pregnancy, which is temporally associated with initiation of estrogen secretion by elongating pig conceptuses [108]. Estrogens, either secreted by the conceptus or injected, induce a transient release of calcium into the uterine lumen within 12 h. Reuptake of that calcium by endometrial and/or conceptus tissues occurs about 12 h after concentrations of calcium in uterine secretions reach maximum values.…”

Section: Endocrine-exocrine Theory Of Pregnancy Recognition In Pigsmentioning

confidence: 99%

Conceptus signals for establishment and maintenance of pregnancy

Spencer

2004

Animal Reproduction Science

164

202

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Establishment and maintenance of pregnancy results from signaling by the conceptus (embryo/fetus and associated extraembryonic membranes) and requires progesterone produced by the corpus luteum (CL). In most mammals, hormones produced by the trophoblast maintain progesterone production by acting directly or indirectly to maintain the CL. In domestic animals (ruminants and pigs), hormones from the trophoblast are antiluteolytic in that they act on the endometrium to prevent uterine release of luteolytic prostaglandin F2 alpha (PGF). In cyclic and pregnant sheep, progesterone negatively autoregulates expression of the progesterone receptor (PR) gene in the endometrial luminal (LE) and superficial glandular epithelium (GE). Available evidence in cyclic sheep indicates that loss of the PR is closely followed by increases in epithelial estrogen receptors (ER) and then oxytocin receptors (OTR), allowing oxytocin to induce uterine release of luteolytic PGF pulses. In pregnant sheep, the conceptus trophoblast produces interferon tau (IFN tau) that acts on the endometrium to inhibit transcription of the ER alpha gene directly and the OTR gene indirectly to abrogate development of the endometrial luteolytic mechanism. Subsequently, sequential, overlapping actions of progesterone, IFN tau, placental lactogen (PL) and growth hormone (GH) comprise a hormonal servomechanism that regulates endometrial gland morphogenesis and terminal differentiated function to maintain pregnancy in sheep. In pigs, the conceptus trophoblast produces estrogen that alters the direction of PGF secretion from an endocrine to exocrine direction, thereby sequestering luteolytic PGF within the uterine lumen. Conceptus estrogen also increases expression of fibroblast growth factor 7 (FGF-7) in the endometrial LE that, in turn, stimulates proliferation and differentiated functions of the trophectoderm, which expresses the FGF-7 receptor. Strategic manipulation of these physiological mechanisms can offer therapeutic schemes to improve uterine capacity, conceptus survival and reproductive health.

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Section: Endocrine-exocrine Theory Of Pregnancy Recognition In Pigsmentioning

confidence: 99%

Conceptus signals for establishment and maintenance of pregnancy

Spencer

2004

Animal Reproduction Science

164

202

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“…During early pregnancy, the up-regulation of oxytocin receptors and consequently luteolysis is inhibited by secretion of interferon tau (IFN ) from the trophodectoderm from days 12-25 in cattle (Farin et al 1990) and from days 10-21 in sheep (Bazer 1989). IFN suppresses oxytocin receptor expression at the transcription level in sheep (Spencer et al 1995a).…”

Section: Introductionmentioning

confidence: 99%

The effect of pregnancy on the expression of uterine oxytocin, oestrogen and progesterone receptors during early pregnancy in the cow

Robinson¹,

Mann²,

Ge³

et al. 1999

Journal of Endocrinology

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The expression of oxytocin receptor (OTR) in the uterine endometrium plays an important role in the initiation of luteolysis. During early pregnancy, the conceptus secretes interferon tau (IFN ) which inhibits OTR up-regulation and luteolysis. In this study, uterine horn cross sections were collected on day 16 from 15 pregnant cows (PREG), 9 uninseminated controls and 5 inseminated cows with no embryo present. The latter two groups had similar results and were combined to form a single non-pregnant (NP) group. The animals were given an oxytocin challenge shortly before tissue collection to assess prostaglandin F 2 (PGF 2 ) release through the measurement of the metabolite 13,14-dihydro-15-keto PGF 2 (PGFM). The mRNAs for OTR, oestrogen receptor (ER) and progesterone receptor (PR) were localised by in situ hybridisation. The results were quantified by optical density (OD) measurements from autoradiographs using image analysis. OTR protein was measured by autoradiography with iodinated oxytocin antagonist and ER and PR protein was detected by immunocytochemistry. The release of PGFM after the oxytocin challenge was significantly higher in the 14 NP cows (187% 15%) compared with the PREG group (131% 11%) (P<0·01). Low concentrations of OTR mRNA were localised to the luminal epithelium (LE) in 6 out of the 14 NP cows, of which 2 also expressed OTR protein, while OTR mRNA and protein were undetectable in all the pregnant animals. These results indicated that the sampling time coincided with the onset of the luteolytic mechanism in the NP cows. On day 16 ER mRNA was detectable in both the LE and glands of both PREG and NP animals. There were no differences in either ER mRNA or protein between NP and PREG samples. PR mRNA was moderately expressed in the caruncular stroma, with lower levels in the dense caruncular-like stroma and glands. There were no differences between PREG and NP animals. The expression of PR mRNA and protein in the deep glands was variable between animals. These results suggested that, in cows, the presence of an embryo suppressed the expression of OTR, but had no effect on the expression of the transcriptionally regulated ER on day 16.

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“…In pigs, the trophoblast produces estrogens, which are responsible for redirection of uterine PGF2α secretion from endocrine to exocrine secretion and thus prevent luteolysis, which normally occurs on days 15-16 of the estrous cycle (Bazer and Thatcher 1977 ;Spencer and Bazer 2004 ). This switch from endocrine to exocrine secretion starts with embryonic estrogen production between days 10 and 12 (Bazer 1989 ). Nevertheless, in the dog, as in these other species, there must be some kind of synchronization between blastocyst development and uterine preparation for pregnancy in order to support gestation, even though its mechanism is not through suppressing luteolysis.…”

Section: Preimplantation Embryo-maternal Communicationmentioning

confidence: 96%

The Dog: Nonconformist, Not Only in Maternal Recognition Signaling

Kowalewski

Gram

Kautz

et al. 2015

Regulation of Implantation and Establishment of Pregnancy in Mammals

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Although similar at the molecular and cellular levels, endocrine mechanisms governing reproductive function in the domestic dog (Canis familiaris) differ markedly at the regulatory level from those known in other domestic animal species. Some of the events, e.g., the lack of luteolysis in the absence of pregnancy, resulting in similar luteal function and, therefore, hormonal profiles in early pregnant and nonpregnant animals, are species-specific. Consequently, no early gestation marker has so far been identified for the dog. Following implantation, relaxin of fetal placental origin can be detected and used for pregnancy diagnosis. Characterized by the lack of an active luteolytic principle from intra- or extra-luteal sources, the canine reproductive cycle appears to represent a "basic" form of mammalian reproductive function with apparently reduced opportunities for facilitating fecundity and hastening reproduction. Nevertheless, in the dog some kind of mechanism for synchronization between blastocyst development and uterine preparation for pregnancy must have evolved in order to support gestation. Driven by this assumption, studies including our recent investigations have been initiated aimed at characterizing some of the embryo-mediated effects of the preimplantation embryo on the canine uterus. Moreover, the lack of a uterine luteolysin and consequently the absence of a need to develop an antiluteolytic strategy make the dog an interesting model for investigating early evolutionary mechanisms involved in the preparation for implantation and ensuring embryo survival. These mechanisms result in an inverse relationship between the duration of pregnancy and of the nonpregnant cycle in the dog, compared with all other domestic animal species.

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Establishment of pregnancy in sheep and pigs

Cited by 74 publications

References 0 publications

Conceptus signals for establishment and maintenance of pregnancy

Conceptus signals for establishment and maintenance of pregnancy

The effect of pregnancy on the expression of uterine oxytocin, oestrogen and progesterone receptors during early pregnancy in the cow

The Dog: Nonconformist, Not Only in Maternal Recognition Signaling

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