Failure of initiation of parturition after electrocoagulation of the pituitary of the fetal lamb

Liggins, G. C.; Kennedy, P. C.; Holm, L. W.

doi:10.1016/0002-9378(67)90031-2

Cited by 208 publications

(55 citation statements)

References 15 publications

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“…In the sheep fetus, plasma cortisol concentrations increase from approximately 125 days of gestation, and this prepartum rise in fetal cortisol concentrations is a consequence of a pituitary-dependent increase in fetal adrenal growth and steroidogenesis [3][4][5]. Before the prepartum increase in fetal plasma cortisol concentrations, an intrafetal infusion of adrenocorticotropic hormone (ACTH) significantly increases the steroidogenic capacity of the fetal adrenal by increasing expression of the adrenal steroidogenic enzymes as well as cytochrome P450 cholesterol side-chain cleavage (CYP11A1) and cytochrome P450 17␣-hydroxylase (CYP17) mRNA [6].…”

Section: Introductionmentioning

confidence: 99%

Differential Actions of Metyrapone on the Fetal Pituitary-Adrenal Axis in the Sheep Fetus in Late Gestation1

Warnes

McMillen

Robinson

et al. 2004

Biology of Reproduction

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It is not clear if an increase in intra-adrenal cortisol is required to mediate the actions of adrenocorticotropic hormone (ACTH) on adrenal growth and steroidogenesis during the prepartum stimulation of the fetal pituitary-adrenal axis. We infused metyrapone, a competitive inhibitor of cortisol biosynthesis, into fetal sheep between 125 and 140 days of gestation (term = 147 +/- 3 days) and measured fetal plasma cortisol, 11-desoxycortisol, and ACTH; pituitary pro-opiomelanocortin mRNA and adrenal expression of ACTH receptor (melanocortin type 2 receptor), steroidogenic acute regulatory protein (StAR), 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2), cytochrome P450 cholesterol side-chain cleavage (CYP11A1), cytochrome P450 17-hydroxylase (CYP17), 3beta-hydroxysteroid dehydrogenase, and cytochrome P450 21-hydroxylase mRNA; and StAR protein in the fetal adrenal gland. Plasma ACTH and 11-desoxycortisol concentrations were higher (P < 0.05), whereas plasma cortisol concentrations were not significantly different in metyrapone- compared with vehicle-infused fetuses. The ratio of plasma cortisol to ACTH concentrations was higher (P < 0.0001) between 136 and 140 days than between 120 and 135 days of gestation in both metyrapone- and vehicle-infused fetuses. The combined adrenal weight and adrenocortical thickness were greater (P < 0.001), and cell density was lower (P < 0.01), in the zona fasciculata of adrenals from the metyrapone-infused group. Adrenal StAR mRNA expression was lower (P < 0.05), whereas the levels of mature StAR protein (30 kDa) were higher (P < 0.05), in the metyrapone-infused fetuses. In addition, adrenal mRNA expression of 11betaHSD2, CYP11A1, and CYP17 were higher (P < 0.05) in the metyrapone-infused fetuses. Thus, metyrapone administration may represent a unique model that allows the investigation of dissociation of the relative actions of ACTH and cortisol on fetal adrenal steroidogenesis and growth during late gestation.

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Section: Introductionmentioning

confidence: 99%

Differential Actions of Metyrapone on the Fetal Pituitary-Adrenal Axis in the Sheep Fetus in Late Gestation1

Warnes

McMillen

Robinson

et al. 2004

Biology of Reproduction

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“…To date, nothing is known about placental glucose transporters or the rate of uteroplacental glucose consumption in the postmature HX fetus, although there are changes in placental ultrastructure in these animals, which may influence nutrient transfer (41). Whatever their cause, the reduced rates of umbilical uptake of glucose and O 2 in the postmature HX fetus do not appear to be too detrimental because HX fetuses maintain their preterm CRL increment during the extended period of gestation and survive in utero for up to 50 d beyond normal term (5,6,15).…”

Section: Discussionmentioning

confidence: 95%

“…In sheep, fetal hypophysectomy prevents the onset of labor and prolongs gestation indefinitely (15). The HX fetus continues to gain weight during the extended period of gestation but does not appear to elongate its limbs after normal term (5,6,9).…”

mentioning

confidence: 98%

Effects of Pituitary Hormone Deficiency on Growth and Glucose Metabolism of the Sheep Fetus

Fowden

Forhead

2007

Endocrinology

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Pituitary hormones are essential for normal growth and metabolic responsiveness after birth, but their role before birth remains unclear. This study examined the effects of hypophysectomizing fetal sheep on their growth and glucose metabolism during the late normal and extended periods of gestation, and on their metabolic response to maternal fasting for 48 h near term. Fetal hypophysectomy reduced crown rump length (CRL), limb lengths, and body weight but increased ponderal index relative to controls near normal term. It also lowered the daily rate of crown rump length increment uniformly from 35 d before, to 20 d after normal term. Hypophysectomized (HX) fetuses had normal weight-specific rates of umbilical uptake, utilization, and oxidation of glucose but lower rates of umbilical oxygen uptake than controls near term. All these metabolic rates were significantly less in HX fetuses during the extended period of gestation than in HX and intact fetuses near normal term. In contrast to controls, glucogenesis was negligible in HX fetuses during maternal fasting. Consequently, the rate of glucose utilization decreased significantly in fasted HX but not intact fetuses. Conversely, the rate of CO(2) production from glucose carbon decreased in fasted intact but not HX fetuses. Fetal hypophysectomy also prevented the fasting-induced increases in plasma cortisol and norepinephrine concentrations seen in controls. These findings demonstrate that the pituitary hormones are important in regulating the growth rate and adaptive responses of glucose metabolism to undernutrition in fetal sheep. They also suggest that fetal metabolism is altered when gestational length is extended.

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“…Liggins et al [17] were the first to report that the fetal hypothalamus is involved in the onset of parturition. In sheep, the fetal hypothalamo-pituitary-adrenal axis regulates the onset of parturition by triggering a sequential process, including an increase in fetal serum cortisol …”

Section: Discussionmentioning

confidence: 98%

Stimulation of Fetal Hypothalamus Induces Uterine Contractions in Pregnant Rats at Term1

Endoh

Fujioka

Endo

et al. 2008

Biology of Reproduction

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The fetal brain is thought to have a role in the onset and progression of labor. Evidence also exists for fetal oxytocin release just before and during parturition. The present study examined whether activation of the fetal brain could induce uterine myometrial contractions through oxytocin receptors in the dam. Under urethane anesthesia, electrical stimulation of the hypothalamus of fetal rats that were still connected with the dams by an intact umbilical cord induced uterine contractions in term pregnant rats. Intraperitoneal injections of synthetic oxytocin in fetuses induced uterine contractions in the dams similar to those induced by electrical stimulation of the fetal hypothalamus. Maternal intravenous injections of an oxytocin antagonist immediately attenuated uterine contractions induced by fetal oxytocin injections and electrical stimulation of the fetal hypothalamus. These findings suggest the possibility that oxytocin released from the fetal hypothalamus is involved in parturition.

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Failure of initiation of parturition after electrocoagulation of the pituitary of the fetal lamb

Cited by 208 publications

References 15 publications

Differential Actions of Metyrapone on the Fetal Pituitary-Adrenal Axis in the Sheep Fetus in Late Gestation1

Differential Actions of Metyrapone on the Fetal Pituitary-Adrenal Axis in the Sheep Fetus in Late Gestation1

Effects of Pituitary Hormone Deficiency on Growth and Glucose Metabolism of the Sheep Fetus

Stimulation of Fetal Hypothalamus Induces Uterine Contractions in Pregnant Rats at Term1

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