Concentrations of prolactin in the plasma of fetal sheep and in amniotic fluid in late gestation and during dexamethasone-induced parturition

McMillen, I. C.; Jenkin, Graham; Robinson, Jeffrey S.; Thorburn, G. D.

doi:10.1677/joe.0.0990107

Cited by 14 publications

(8 citation statements)

References 23 publications

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“…It has also been demonstrated, however, that there is a cortisol-dependent increase in the expression of PRLR1 and PRLR2 in the fetal liver during late gestation (34). Furthermore, although circulating fetal PRL concentrations may vary between animals depending on the external photoperiod and level of fetal nutrition (2,17,35), plasma PRL concentrations tend to increase in fetal sheep during the last week of gestation (15,30). We investigated the role of endogenous PRL in the maintenance of hepatic SOCS-3 expression using the dopamine agonist Bromo to suppress pituitary PRL secretion in the late gestation fetus (16,27).…”

Section: Discussionmentioning

confidence: 99%

Differential regulation of suppressor of cytokine signaling-3 in the liver and adipose tissue of the sheep fetus in late gestation

Gentili

Waters²,

McMillen³

2006

American Journal of Physiology-Regulatory, Integrative and Comp

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It is unknown whether the JAK/STAT/suppressor of cytokine signaling-3 (SOCS-3) intracellular signaling pathway plays a role in tissue growth and metabolism during fetal life. We investigated whether there is a differential profile of SOCS-3 expression in the liver and perirenal adipose tissue during the period of increased fetal growth in late gestation and the impact of fetal growth restriction on SOCS-3 expression in the fetal liver. We also determined whether basal SOCS-3 expression in the fetal liver and perirenal adipose tissue is regulated by endogenous fetal prolactin (PRL). SOCS-3 mRNA abundance was higher in the liver than in the pancreas, spleen, and kidney of the sheep fetus during late gestation. In the liver, SOCS-3 mRNA expression was increased (P < 0.05) between 125 (n = 4) and 145 days (n = 7) gestation and lower (P < 0.05) in growth-restricted compared with normally grown fetal sheep in late gestation. The relative expression of SOCS-3 mRNA in the fetal liver was directly related to the mean plasma PRL concentrations during a 48-h infusion of either a dopaminergic agonist, bromocriptine (n = 7), or saline (n = 5), such that SOCS-3 mRNA expression was lower when plasma PRL concentrations decreased below approximately 20 ng/ml [y = 0.99 - (2.47/x) + (4.96/x(2)); r(2) = 0.91, P < 0.0001, n = 12]. No relationship was shown between the abundance of phospho-STAT5 in the fetal liver and circulating PRL. SOCS-3 expression in perirenal adipose tissue decreased (P < 0001) between 90-91 (n = 6) and 140-145 days (n = 9) gestation and was not related to endogenous PRL concentrations. Thus SOCS-3 is differentially expressed and regulated in key fetal tissues and may play an important and tissue-specific role in the regulation of cellular proliferation and differentiation before birth.

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Section: Discussionmentioning

confidence: 99%

Differential regulation of suppressor of cytokine signaling-3 in the liver and adipose tissue of the sheep fetus in late gestation

Gentili

Waters²,

McMillen³

2006

American Journal of Physiology-Regulatory, Integrative and Comp

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“…In earlier reports on the ontogeny of prolactin secretion in fetal lambs, little or no information about the ambient photoperiod was provided (Mueller, Gluckman, Kaplan et al 1979;McMillen, Jenkin, Robinson & Thorburn, 1983), so it is impossible to determine the extent to which results reported may have been influenced either by the current photo¬ period or by the photoperiodic history of the ewe before housing for the study. Lambs born during the natural breeding season would have been exposed to effects on the maternal melatonin rhythm of the rapidly increasing photoperiod during early spring, so increasing prolactin concentrations would be expected during late fetal life.…”

Section: Discussionmentioning

confidence: 99%

“…It did not occur where photo¬ period was constant for 3 weeks or more. Differences in ambient photoperiod may also explain many of the differences among individuals noted by McMillen et al (1983).…”

Section: Discussionmentioning

confidence: 99%

Effects of altered photoperiod or maternal melatonin administration on plasma prolactin concentrations in fetal lambs

Bassett¹,

Curtis²,

Hanson³

et al. 1989

Journal of Endocrinology

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During winter (December to March), when late-pregnant ewes were maintained under an artificial long-day photoperiod (16 h light) for 3 weeks or more before insertion of fetal vascular cannulae between 118 and 120 days of gestation (full term, 147 days), plasma prolactin concentrations in their fetal lambs were significantly increased throughout the last 3 weeks of gestation in comparison with values in similar aged fetuses from ewes experiencing only the natural short-day (less than 9 h light) winter photoperiod. When additional lighting was given only after vascular cannulation, fetal plasma prolactin increased steadily from low values, characteristic of winter pregnancies, to high values, characteristic of long-day (16 h light:8 h darkness) pregnancies. Maternal plasma prolactin concentrations changed in a similar way. During summer pregnancies (greater than 16 h light), plasma prolactin in fetal lambs was significantly reduced within 48 h when ewes were given melatonin by i.v. infusion for 14 h each night to simulate the winter duration of the nocturnal increase in plasma melatonin. Maternal plasma prolactin concentrations also decreased significantly when melatonin was given for 3 weeks, but not in a shorter experiment. Increases in fetal plasma prolactin were proportional to the basal prolactin concentration in fetuses injected i.v. with TRH or a dopaminergic antagonist, metoclopramide, to assess how photoperiod influenced the responsiveness of prolactin secretion to acute stimulation. The results confirm that photoperiod, rather than developmental maturity, is the principal determinant of plasma prolactin in the fetal lamb during the last third of gestation, and provide evidence that photoperiodic information is transmitted to the fetus through the diurnal rhythm of melatonin in the ewe.

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“…Plasma concentrations of prolactin and GH were measured by radioimmunoassay as previously de¬ scribed (McMillen, Jenkin, Robinson & Thorburn, 1983;Parkes, 1983) with the infused hormone prepa¬ rations used as assay standards. The minimum detect¬ able levels of prolactin and GH were 0-4 and 5 pg/1 respectively.…”

Section: Assaysmentioning

confidence: 99%

Antagonism by growth hormone of insulin action in fetal sheep

Parkes¹,

Bassett²

1985

Journal of Endocrinology

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Insulin, glucose, lactate and alpha-amino acid nitrogen concentrations were measured in the plasma of ewes and their hypophysectomized fetal lambs during intravenous infusions of GH, prolactin or saline into the fetus in utero. Prolactin and saline had no effect on mother or fetus. Infusion of GH at 1.2 mg/kg per day for 2 days or at 0.4 mg/kg per day for 4 days caused a sustained twofold increae in the level of insulin and a smaller, but sustained, increase in the level of glucose in fetal plasma. We suggest that GH antagonizes the action of insulin in the fetus. Glucose supplies to the fetal brain and placenta may be protected by such antagonism of insulin use during glucose shortage.

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Concentrations of prolactin in the plasma of fetal sheep and in amniotic fluid in late gestation and during dexamethasone-induced parturition

Cited by 14 publications

References 23 publications

Differential regulation of suppressor of cytokine signaling-3 in the liver and adipose tissue of the sheep fetus in late gestation

Differential regulation of suppressor of cytokine signaling-3 in the liver and adipose tissue of the sheep fetus in late gestation

Effects of altered photoperiod or maternal melatonin administration on plasma prolactin concentrations in fetal lambs

Antagonism by growth hormone of insulin action in fetal sheep

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