Influence of Estradiol and Progesterone withdrawal on the Secretion of and the Temporal Correlation between Pulses of Oxytocin and Prostaglandin F2α, in Ewes1

Walker, Denise L.; Weston, P G; Hixon, J. E.

doi:10.1095/biolreprod56.5.1228

Cited by 6 publications

(2 citation statements)

References 53 publications

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“…On the other hand, the lower frequency of OT peaks in CAP-treated gilts as compared to saline-treated ones was accompanied with the lower frequency of PGFM surges. Recent studies by Walker et al (1997) have revealed in ewes that pulses of PGF = which were linked to OT secretion ranged from 36% to 53%. These pulses had a longer duration and a higher amplitude than pulses that were not linked.…”

Section: Discussionmentioning

confidence: 99%

Effect of an Oxytocin Antagonist on Prostaglandin F2α Secretion and the Course of Luteolysis in Sows

Kotwica¹,

Franczak²,

Okrasa³

et al. 1999

Acta Veterinaria Hungarica

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The role of oxytocin (OT) in the regulation of prostaglandin F2 alpha (PGF2 alpha) secretion during luteolysis in gilts was studied using a highly specific OT antagonist (CAP-581). In Experiment 1 gilts on Days 14 to 19 of the oestrous cycle in Latin square design were used, to determine the dose and time of application of OT and CAP. In Group I (n = 6) gilts were treated intravenously with saline or with 10, 20 and 30 IU of OT. Concentrations of the main PGF2 alpha metabolite i.e. 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) were measured in blood samples as uterine response to the treatment. Twenty IU of OT was the most effective to stimulate PGFM release and this dose was used after CAP treatment in gilts of Groups II, III and IV. Gilts of Group II (n = 3) were injected into the uterine horns (UH) with saline (5 ml/horn) or CAP (2 mg, 3 mg and 4 mg; half dose/horn) and OT was injected (i.v.) 30 min thereafter. Any of the CAP doses given into the UH affected PGFM plasma concentrations stimulated by OT. In Group III (n = 4) gilts were infused (i.v.) for 30 min with CAP (9 mg, 14 mg and 18 mg/gilt) followed by 20 IU of OT. All doses of CAP effectively inhibited OT-stimulated PGF2 alpha release, therefore 9 mg was selected for the further studies. Gilts of Group IV (n = 4) received OT 4, 6 and 8 h after CAP to define how long CAP blocks the OT receptors. Concentrations of PGFM increased after any of this period of time. Thus, we concluded that 9 mg of CAP infused every 4 h will effectively block OT receptors. In Experiment 2, gilts (n = 4) received CAP as a 30-min infusion every 4 h on Days 12-20 of the oestrous cycle. Control gilts (n = 3) were infused with saline. CAP infusions diminished the height of PGFM peaks (P < 0.05). Frequency of the PGFM (P < 0.057) and OT (P < 0.082) peaks only tended to be lower in the CAP-treated gilts. Peripheral plasma concentrations of progesterone (P4) and oestradiol-17 beta (E2) and the time of luteolysis initiation as measured by the decrease of P4 concentration were the same in CAP- and saline-treated gilts. The macroscopic studies of the ovaries in gilts revealed lack of differences between groups. We conclude that OT is involved in the secretion of luteolytic PGF2 alpha peaks but its role is limited to controlling their height and frequency. Blocking of OT receptors did not prevent luteolysis in sows.

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Section: Discussionmentioning

confidence: 99%

Effect of an Oxytocin Antagonist on Prostaglandin F2α Secretion and the Course of Luteolysis in Sows

Kotwica¹,

Franczak²,

Okrasa³

et al. 1999

Acta Veterinaria Hungarica

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“…336). Oxytocin (157,237,377) stimulates synthesis and secretion of PGF 2␣ from the uterus of guinea pigs (200), heifers (197,308), mares (127), sows (186), and ewes (376). It has recently been proposed that release of luteal PGF 2␣ amplifies the luteolytic signal in an autocrine or paracrine manner (263,369,370).…”

Section: Luteolysismentioning

confidence: 99%

Mechanisms Controlling the Function and Life Span of the Corpus Luteum

Niswender

Juengel

Silva

et al. 2000

Physiological Reviews

857

553

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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 follicular granulosal and thecal cells after ovulation. Luteinizing hormone (LH) from the anterior pituitary is important for normal development and function of the corpus luteum in most mammals, although growth hormone, prolactin, and estradiol also play a role in several species. The mature corpus luteum is composed of at least two steroidogenic cell types based on morphological and biochemical criteria and on the follicular source of origin. Small luteal cells appear to be of thecal cell origin and respond to LH with increased secretion of progesterone. LH directly stimulates the secretion of progesterone from small luteal cells via activation of the protein kinase A second messenger pathway. Large luteal cells are of granulosal cell origin and contain receptors for PGF(2alpha) and appear to mediate the luteolytic actions of this hormone. If pregnancy does not occur, the corpus luteum must regress to allow follicular growth and ovulation and the reproductive cycle begins again. Luteal regression is initiated by PGF(2alpha) of uterine origin in most subprimate species. The role played by PGF(2alpha) in primates remains controversial. In primates, if PGF(2alpha) plays a role in luteolysis, it appears to be of ovarian origin. The antisteroidogenic effects of PGF(2alpha) appear to be mediated by the protein kinase C second messenger pathway, whereas loss of luteal cells appears to follow an influx of calcium, activation of endonucleases, and an apoptotic form of cell death. If the female becomes pregnant, continued secretion of progesterone from the corpus luteum is required to provide an appropriate uterine environment for maintenance of pregnancy. The mechanisms whereby the pregnant uterus signals the corpus luteum that a conceptus is present varies from secretion of a chorionic gonadotropin (primates and equids), to secretion of an antiluteolytic factor (domestic ruminants), and to a neuroendocrine reflex arc that modifies the secretory patterns of hormones from the anterior pituitary (most rodents).

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Intrinsically Fluorescent Luteinizing Hormone Receptor Demonstrates Hormone-Driven Aggregation

Nelson

et al. 1999

Biochemical and Biophysical Research Communications

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Influence of Estradiol and Progesterone withdrawal on the Secretion of and the Temporal Correlation between Pulses of Oxytocin and Prostaglandin F2α, in Ewes1

Cited by 6 publications

References 53 publications

Effect of an Oxytocin Antagonist on Prostaglandin F2α Secretion and the Course of Luteolysis in Sows

Effect of an Oxytocin Antagonist on Prostaglandin F2α Secretion and the Course of Luteolysis in Sows

Mechanisms Controlling the Function and Life Span of the Corpus Luteum

Intrinsically Fluorescent Luteinizing Hormone Receptor Demonstrates Hormone-Driven Aggregation

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