In vitro maturation of ovine fetal adrenal cells adenylate cyclase: Corticotropin-dependent and independent development of the response to corticotropin

Durand, Philippe; Cathiard, Anne-Marie; Saez, J.M.

doi:10.1016/0006-291x(82)92050-2

Cited by 31 publications

(7 citation statements)

References 15 publications

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“…Jones & Roebuck (1980) suggested that the ability of the ovine fetal adrenal gland to respond to circulating ACTH in vivo was suppressed by some factor(s), since they found a discrepancy between adrenal cortisol responses to ACTH in vitro and in vivo. In support of this proposal, adrenal cells from 120-day-old fetuses, maintained in an ACTH-free medium, exhibit enhanced responsiveness as the time in culture increases, suggesting the existence of an inhibitor of ACTH action in vivo (Durand et al 1982). It has been suggested that these putative inhibitory factors are the high molecular weight (HMW) precursor peptides of ACTH itself, since these peptides have been shown to inhibit ACTH-induced cortisol secretion from adrenal cells in vitro (Roebuck et al 1980, Jones et al 1992.…”

Section: Introductionmentioning

confidence: 78%

“…It has been suggested that these putative inhibitory factors are the high molecular weight (HMW) precursor peptides of ACTH itself, since these peptides have been shown to inhibit ACTH-induced cortisol secretion from adrenal cells in vitro (Roebuck et al 1980, Jones et al 1992. As the HMW ACTH-containing peptides are present in fetal plasma in high concentrations (Saphier et al 1993, Carr et al 1995, recent attention has therefore focused on the ratio of low molecular weight (LMW) to HMW ACTH, since it has been proposed that the balance between the stimulatory action of ACTH and the proposed inhibitory action of the HMW ACTH precursor peptides is involved in the regulation of fetal adrenal responsiveness and basal cortisol secretion (Roebuck et al 1980, Durand et al 1982. It has been speculated that the successful establishment of labour in HX fetuses receiving a constant maintenance infusion of ACTH reflects an enhanced responsiveness of the adrenal glands of these fetuses to ACTH ( Jacobs et al 1994).…”

Section: Introductionmentioning

confidence: 99%

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Studies on the role of ACTH in the regulation of adrenal responsiveness and the timing of parturition in the ovine fetus

Poore¹,

Young²,

Canny³

et al. 1998

Journal of Endocrinology

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A dramatic late-gestation increase in fetal plasma cortisol concentrations is critical for the timing of parturition in the sheep. This increase appears to depend upon an intact hypothalamo-pituitary unit and is characterised by increasing responsiveness of the fetal adrenal gland to ACTH. ACTH has been postulated as the critical determinant of the late-gestation cortisol increase; however, recent evidence has suggested that other factors, including the ACTH precursor, pro-opiomelanocortin, may also be involved. To further define the role of ACTH in determining the timing of parturition and the responsiveness of the fetal adrenal gland, intact (INT/ACTH) and hypophysectomised (HX/ACTH) fetuses received a continuous infusion of ACTH from the time of surgery (115 days gestational age (GA)) at a rate we have previously shown to generate normal fetal cortisol concentrations and term parturition in HX fetuses. A third group of saline-infused intact fetuses (INT/SAL) served as the control group. Adrenal responsiveness was assessed by cortisol responses to ACTH challenges at 120, 130 and 140 days GA.There were no differences between the three groups of fetuses in the timing of parturition, the late-gestation increase in cortisol concentrations or the size of the adrenal cortex. In both INT/SAL and INT/ACTH fetuses, there were significant increases in basal immunoreactive-ACTH concentrations with advancing GA, although no such increase was observed in HX/ACTH fetuses. The proportion of total ACTH immunoreactivity present in low molecular weight (LMW) forms in INT/ACTH fetuses was greater than that in INT/SAL fetuses, while the level of LMW ACTH in HX/ACTH fetuses was intermediate. Both ACTH (1-24) -infused groups of fetuses had dramatically enhanced adrenal responsiveness to ACTH at all GAs tested when compared with INT/SAL fetuses and there was a correlation (in rank order) between the proportion of LMW ACTH immunoreactivity and adrenal responsiveness.From these observations it appears that there is a separate regulation of adrenal responsiveness from basal cortisol concentrations and that an increase in basal cortisol concentrations can occur in the absence of an increase in basal ACTH concentrations. Furthermore, an increase in adrenal responsiveness does not appear to predict the timing of parturition nor basal cortisol concentrations. Taken together with previous studies it appears that ACTH plays an essential role in maintaining the growth of the fetal adrenal and enhancing its responsiveness, but a late-gestation increase in ACTH concentrations is not required to regulate basal cortisol concentrations or the timing of parturition.

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Section: Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Studies on the role of ACTH in the regulation of adrenal responsiveness and the timing of parturition in the ovine fetus

Poore¹,

Young²,

Canny³

et al. 1998

Journal of Endocrinology

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“…The pituitary secretes less of this precursor as the fetus develops, with the result that the adrenal becomes more responsive to ACTH and corticosteroid production increases (Jones and Roebuck 1980). Support for this proposal comes from in vitrs studies that demonstrate spontaneous production of steroids and adenylate cyclase activity from sheep fetal adrenal tissue maintained in culture, data consistent with removal of an in vtvs inhibitory influence during in vitro culture (Durand et al 1982). Recent methodological improvements for the radioimmunoassay of ACTH in unextracted plasma and more stable chronic fetal sheep preparations have enabled subtle changes in ACTH in the fetal circulation to be detected.…”

Section: Ontogeny Of Basal Acth and Cortisol Secretionmentioning

confidence: 50%

Regulation of the hypothalamic–pituitary–adrenal axis in birth

An¹,

Challis²

1988

Can. J. Physiol. Pharmacol.

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In sheep an increase in fetal pituitary-adrenal function, reflected in rising concentrations of plasma ACTH and cortisol, is important in relation to fetal organ maturation and the onset of parturition. This review presents evidence that implicates the hypothalamic-pituitary-adrenal axis in the control of parturition and describes recent experiments that explore in detail the maturation of the fetal hypothalamus and pituitary in relation to fetal adrenal function. Recent improvements for the measurement of ACTH in unextracted plasma and the ability to maintain vascular catheters in chronically catheterized fetal sheep have enabled subtle changes in fetal ACTH concentrations to be detected. As a result of these advances it has now been established that the terminal rise in cortisol, which is responsible for the onset of parturition in sheep, is preceded by an increase in fetal plasma ACTH concentrations. This has led to the hypothesis that birth results from the sequential development of the fetal hypothalamic-pituitary-adrenal axis with the signal originating from the fetal brain. This increase in trophic drive to the fetal adrenal may result from changes in the responsiveness of the fetal pituitary gland to factors that stimulate the release of ACTH. Corticotropin releasing factor (CRF) and arginine vasopressin are two such factors that stimulate the secretion of ACTH and cortisol secretion in the chronically catheterized fetal sheep. The response to these factors increases with gestational age and is sensitive to glucocorticoid feedback. Furthermore, repeated administration of CRF to immature fetal sheep results in pituitary and adrenal activation and in some cases may lead to premature parturition.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…1982). Contributing to the rise in adrenal sensitivity is an overall increase in the rate of growth of the adrenal cortex (Nathanielsz 1976) and an increase in the cellular sensitivity to ACTH (Durand et al 1981(Durand et al , 1982(Durand et al , 1984. However, in addition to the changes occuning within the adrenal cortex, are changes in the processing and secretion of proopiomelanocortin (POMC; the precursor for ACTH) melanocyte stimulating hormone (MSH), P-endorphin, and lipotrophin (Yang et al 1991;Merei et al 1993;Myers et al 1993;Saoud and Wood 1996b).…”

Section: The Simple System: the Ovine Fetal Hpa Axismentioning

confidence: 99%

Development of the hypothalamus‐pituitary‐adrenal axis of the equine fetus: A comparative review

Wood

Cudd²

1997

Equine Veterinary Journal

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In vitro maturation of ovine fetal adrenal cells adenylate cyclase: Corticotropin-dependent and independent development of the response to corticotropin

Cited by 31 publications

References 15 publications

Studies on the role of ACTH in the regulation of adrenal responsiveness and the timing of parturition in the ovine fetus

Studies on the role of ACTH in the regulation of adrenal responsiveness and the timing of parturition in the ovine fetus

Regulation of the hypothalamic–pituitary–adrenal axis in birth

Development of the hypothalamus‐pituitary‐adrenal axis of the equine fetus: A comparative review

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