Developmental and glucocorticoid regulation of pituitary 11 β-hydroxysteroid dehydrogenase 1 gene expression in the ovine fetus and lamb

1995 ◽  
Vol 14 (1) ◽  
pp. 109-116 ◽  
Author(s):  
K Yang ◽  
S G Matthews ◽  
J R G Challis
Keyword(s):  
Reductase Activity ◽  
Hydroxysteroid Dehydrogenase ◽  
Postnatal Period ◽  
Pars Intermedia ◽  
Pars Distalis ◽  
Short Term ◽  
Fetal Sheep ◽  
Ovine Fetus

ABSTRACT To examine the role of 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) in the control of glucocorticoid actions in the ovine pituitary during development, we have sought developmental changes in the distribution and the level of 11β-HSD1 mRNA by in situ hybridization. In the pars distalis, 11β-HSD1 mRNA was present by day 60; its amount did not change significantly until term (days 145–147) when it increased dramatically. The level of 11β-HSD1 mRNA increased further during the postnatal period. In contrast, 11β-HSD1 mRNA in the pars intermedia was not detectable until day 135; it increased in amount at days 140–143, but did not change significantly thereafter through to adulthood. We have also measured levels of both dehydrogenase and reductase activities of 11β-HSD1 in the pars distalis of fetal sheep at day 140 and term, and of postnatal sheep at 1–2 months of age, to determine whether changes in 11β-HSD1 mRNA are reflected in the levels of enzyme activities. There were progressive increases in both dehydrogenase and reductase activities from day 140 to 1–2 months postnatally, although dehydrogenase activity was consistently higher than reductase activity. Finally, we have determined the effect of short-term intrafetal cortisol infusion (5 μg/min for 12 h) on levels of pituitary 11β-HSD1 mRNA by in situ hybridization. There was no effect of cortisol infusion on 11β-HSD1 mRNA expression. The present results demonstrate that 11β-HSD mRNA and enzyme activity in the pars distalis of fetal sheep increase dramatically at term when plasma levels of both ACTH and cortisol are elevated. This suggests that 11β-HSD1 may contribute to the proposed resetting of cortisol negative feedback within the fetal pituitary at that time.

Changes in glucocorticoid receptor mRNA in the developing ovine pituitary and the effects of exogenous cortisol

1995 ◽  
Vol 144 (3) ◽  
pp. 483-490 ◽  
Author(s):  
S G Matthews ◽  
K Yang ◽  
J R G Challis
Keyword(s):  
Glucocorticoid Receptor ◽  
Late Gestation ◽  
Developmental Changes ◽  
Pars Intermedia ◽  
Pars Distalis ◽  
Short Term ◽  
Neonatal Life ◽  
Inferior Aspect ◽  
Glucocorticoid Receptor Mrna

Abstract Developmental changes in pituitary glucocorticoid receptor (GR) mRNA were examined during gestation and early neonatal life using in situ hybridization. Pituitaries were harvested from sheep fetuses at days 60–80, 100–120, 130–135, 140–142 and term, and from lambs of days 0–7 and 30–60, and adults. GR mRNA was present in the pars distalis by day 60, levels increased through gestation, and there was a redistribution of GR mRNA, resulting in a relatively greater abundance at the base of the pars distalis. At term, there was a significant (P<0·05 compared with the day 140–142 fetuses) elevation of GR mRNA, which was maintained in the newborn lamb, reaching highest levels at days 30–60 of neonatal life. GR mRNA was undetectable in the pars intermedia until day 120, but subsequently increased to high levels at term. Interestingly, the expression of GR mRNA in the pars intermedia dropped precipitously in the newborn (P<0·05 compared with term), though levels recovered in the older lambs and adults. The regional and cellular distribution of GR mRNA correlated closely with the presence of immuno-reactive GR (irGR) in the pituitary; the majority of irGR was present in the nuclei. Intrafetal infusion of cortisol (12 h; 5 μg/min) in late gestation (day 135) had no effect on GR mRNA expression in either the pars distalis or pars intermedia. These results indicated that, in the fetal pituitary, (1) the GR gene is expressed in both the pars distalis and pars intermedia, (2) levels of GR mRNA in the fetal pituitary correlated with the distribution of nuclear irGR, (3) GR mRNA is present at higher levels in the inferior aspect of the pars distalis, its abundance increases immediately prior to parturition and is maintained in the newborn, and (4) cortisol infusion for 12 h does not affect GR mRNA in either region of the pituitary, suggesting that, in the short term, glucocorticoids do not directly regulate GR synthesis. Journal of Endocrinology (1995) 144, 483–490

Developmental changes in the distribution of pro-opiomelanocortin and prolactin mRNA in the pituitary of the ovine fetus and lamb

1994 ◽  
Vol 13 (2) ◽  
pp. 175-185 ◽  
Author(s):  
S G Matthews ◽  
X Han ◽  
F Lu ◽  
J R G Challis
Keyword(s):  
Late Gestation ◽  
Pars Intermedia ◽  
Fetal Life ◽  
Mrna Levels ◽  
Pars Distalis ◽  
Pomc Mrna ◽  
Inferior Aspect ◽  
Ovine Fetus ◽  
Pomc Gene

ABSTRACT Ontogenic changes in pituitary pro-opiomelanocortin (POMC) mRNA and prolactin (PRL) mRNA were examined during gestation and early neonatal life using in situ hybridization histochemistry. Pituitaries were harvested from fetuses at days 60–80, 100–120, 135–140 and 142–143 of gestation and at term, and from lambs at days 1–7 and 30–60 of age and adults. POMC mRNA, present by day 60, rose during mid- and late gestation. Concurrently there was a change in corticotroph distribution, resulting in a relatively greater quantity of POMC mRNA at the base of the pars distalis. At term, there was a significant (P<0·05) further elevation of POMC mRNA. POMC mRNA levels remained high in the newborn lamb but decreased in the adult. Cells in the pars intermedia expressed large amounts of POMC mRNA early in fetal life and this pattern persisted throughout gestation and into the neonatal period. Changes in the expression of the POMC gene correlated closely with the presence of immunoreactive (ir)ACTH in the pituitary; in fetuses the proportion of irACTH-positive cells rose to 10% of pars distalis cells by day 100 and did not change significantly thereafter. The lactotrophs contained PRL mRNA by day 60, and the quantity increased towards parturition (P<0·05). PRL mRNA subsequently decreased in the neonate, but rose as the lamb matured. These results indicate that in the fetal pituitary: (1) the POMC gene is highly expressed during gestation in both the pars distalis and the pars intermedia, (2) changes in the amounts of POMC mRNA and PRL mRNA in the pars distalis correlate with the distribution of irACTH and irPRL respectively, and (3) POMC mRNA is distributed primarily in the inferior aspect of the pars distalis, and in this region its quantity is highest immediately prior to parturition.

Urocortin: a mechanism for the sustained activation of the HPA axis in the late-gestation ovine fetus?

2002 ◽  
Vol 283 (1) ◽  
pp. E165-E171 ◽  
Author(s):  
Alison C. Holloway ◽  
David C. Howe ◽  
Gabriel Chan ◽  
Vicki L. Clifton ◽  
Roger Smith ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Late Gestation ◽  
Pituitary Cells ◽  
Fetal Sheep ◽  
Antisense Probe ◽  
Pomc Mrna ◽  
Ovine Fetus ◽  
Ovine Fetal ◽  
Sustained Activation

We hypothesized that urocortin might be produced in the pituitary of the late-gestation ovine fetus in a manner that could contribute to the regulation of ACTH output. We used in situ hybridization and immunohistochemistry to identify urocortin mRNA and protein in late-gestation fetal pituitary tissue. Levels of urocortin mRNA rose during late gestation and were associated temporally with rising concentrations of pituitary proopiomelanocortin (POMC) mRNA. Urocortin was localized both to cells expressing ACTH and to non-ACTH cells by use of dual immunofluorescence histochemistry. Transfection of pituitary cultures with urocortin antisense probe reduced ACTH output, whereas added urocortin stimulated ACTH output from cultured pituitary cells. Cortisol infusion for 96 h in chronically catheterized late-gestation fetal sheep significantly stimulated levels of pituitary urocortin mRNA. We conclude that urocortin is expressed in the ovine fetal pituitary and localizes with, and can stimulate output of, ACTH. Regulation of urocortin by cortisol suggests a mechanism to override negative feedback and sustain feedforward of fetal hypothalamic-pituitary-adrenal function, leading to birth.

Divergent changes in plasma ACTH and pituitary POMC mRNA after cortisol administration to late-gestation ovine fetus

1998 ◽  
Vol 274 (3) ◽  
pp. E417-E425 ◽  
Author(s):  
T. M. Jeffray ◽  
S. G. Matthews ◽  
G. L. Hammond ◽  
J. R. G. Challis
Keyword(s):  
Plasma Cortisol ◽  
Late Gestation ◽  
Pars Intermedia ◽  
Mrna Levels ◽  
Plasma Acth ◽  
Negative Feedback Regulation ◽  
Fetal Sheep ◽  
Pomc Mrna ◽  
Free Cortisol ◽  
Ovine Fetus

Plasma concentrations of cortisol and adrenocorticotropic hormone (ACTH) rise in the late-gestation sheep fetus at approximately the same time as there is an increase in the plasma levels of corticosteroid- binding globulin (CBG). We hypothesized that intrafetal cortisol infusion during late pregnancy would stimulate an increase in fetal plasma CBG, which in turn would bind cortisol and diminish glucocorticoid negative-feedback regulation of the fetal pituitary, leading to an increase in plasma ACTH concentrations. Cortisol was infused into chronically catheterized fetal sheep beginning at 126.1 ± 0.5 days of gestation and continued for 96 h. Control fetuses were infused with saline. In cortisol-infused fetuses, the plasma cortisol concentrations rose significantly from control levels (4.4 ± 0.6 ng/ml) to 19.3 ± 3.1 ng/ml within 24 h and remained significantly elevated throughout the infusion period. Plasma immunoreactive (ir) ACTH concentrations were significantly elevated in cortisol-infused fetuses within 24–48 h and remained significantly higher than in controls throughout the 96-h experimental period. Plasma free cortisol concentrations increased 10-fold and remained significantly elevated in cortisol-infused animals, despite a rise in plasma corticosteroid-binding capacity. Levels of pituitary proopiomelanocortin (POMC) mRNA in the fetal pars distalis and pars intermedia were 96 and 38% lower, respectively, after 96 h of cortisol infusion. Therefore physiological elevations of plasma cortisol, in the late-gestation ovine fetus, lead to increases in mean plasma irACTH concentrations, but this is not associated with increases in fetal pituitary POMC mRNA levels.

Adaptation to calcium deprivation in the rat: effects of parathyroidectomy.

1977 ◽  
Vol 232 (3) ◽  
pp. E336
Author(s):  
J T Pento ◽  
L C Waite ◽  
P J Tracy ◽  
A D Kenny
Keyword(s):  
Adaptive Response ◽  
Calcium Transport ◽  
Parathyroid Tissue ◽  
Adaptation Period ◽  
Short Term ◽  
High Calcium

The role of parathyroid hormone (PTH) in the adaptive response in gut calcium transport to calcium deprivation has been studied in the rat using both the in vitro everted duodenal sac and the in situ ligated duodenal segment technique. Intact or parathyroidectomized (PTX) young rats were placed on a low calcium (0.01%) diet for 7-, 14-, or 21-day adaptation periods and compared with control rats maintained on a high calcium (1.5%) diet. Prior PTX (3 days before the start of the adaptation period) abolished the adaptive response (enhanced calcium transport) induced by calcium deprivation for a 7-day adaptation period, but did not abolish a response after a 21-day period. A 14-day adaptation period gave equivocal results. It is concluded that PTH appears to be necessary for short-term (7-day) adaptation, but not for long-term (21-day) adaptation to calcium deprivation. However, if accessory parathyroid tissue is present, the data could be interpreted differently: the essentiality of PTH for the adaptive response might be independent of the length of the adaptation period. The data also contribute to a possible resolution of the controversy concerning the involvement of PTH in the regulation of intestinal calcium transport in the rat.

Effects of long-term hypoxemia on pituitary-adrenal function in fetal sheep

1996 ◽  
Vol 271 (4) ◽  
pp. E678-E685 ◽  
Author(s):  
J. Murotsuki ◽  
R. Gagnon ◽  
S. G. Matthews ◽  
J. R. Challis
Keyword(s):  
Adrenal Function ◽  
Arterial Oxygen ◽  
Pars Intermedia ◽  
Mrna Levels ◽  
Pars Distalis ◽  
Fetal Sheep ◽  
Fetal Plasma ◽  
Pomc Mrna ◽  
Pregnant Sheep

To test the hypothesis that long-term hypoxemia causes premature activation of the fetal pituitary-adrenal function, we embolized the fetal side of the placenta in pregnant sheep and examined the changes in concentrations of immunoreactive adrenocorticotropic hormone (irACTH), cortisol, and prostaglandin E2 (PGE2) in fetal plasma, and levels and localization of proopiomelanocortin (POMC) mRNA in the pars distalis and the pars intermedia of the fetal pituitary. Twelve fetal sheep were studied (6 embolized and 6 control) for 21 days between 0.74 and 0.88 of gestation. Daily injections of nonradiolabeled microspheres were given into the fetal abdominal aorta to decrease fetal arterial oxygen content by 40-50% of the preembolization values. In the embolized group, concentrations of irACTH, PGE2, and cortisol in fetal plasma increased gradually and were significantly (P < 0.05) elevated above those of controls after day 10, day 16, and day 20, respectively. POMC mRNA levels in the pars distalis of the fetal pituitary were not different from those of controls but were significantly reduced in the pars intermedia (P < 0.05). We conclude that levels of POMC mRNA in the pars distalis are unchanged during long-term hypoxemia possibly because of negative feedback effects of elevated cortisol on the pituitary gland. During long-term fetal hypoxemia, there is a differential regulation of POMC mRNA expression in the pars distalis and pars intermedia.

Calcium pools, calcium entry, and cell growth

1996 ◽  
Vol 16 (2) ◽  
pp. 139-157 ◽  
Author(s):  
Donald L. Gill ◽  
Richard T. Waldron ◽  
Krystyna E. Rys-Sikora ◽  
Carmen A. Ufret-Vincenty ◽  
Matthew N. Graber ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Morphological Analysis ◽  
Essential Fatty Acids ◽  
Physiological Role ◽  
Wide Distribution ◽  
Short Term ◽  
Growth State

The Ca2+ pump and Ca2+ release functions of intracellular Ca2+ pools have been well characterized. However, the nature and identity of Ca2+ pools as well as the physiological implications of Ca2+ levels within them, have remained elusive. Ca2+ pools appear to be contained within the endoplasmic reticulum (ER); however, ER is a heterogeneous and widely distributed organelle, with numerous other functions than Ca2+ regulation. Studies described here center on trying to determine more about subcellular distribution of Ca2+ pools, the levels of Ca2+ within Ca2+ pools, and how these intraluminal Ca2+ levels may be physiologically related to ER function. Experiments utilizing in situ high resolution subcellular morphological analysis of ER loaded with ratiometric fluroescent Ca2+ dyes, indicate a wide distribution of inositol 1,4,5-trisphosphate (InsP3)-sensitive Ca2+ pools within cells, and large changes in the levels of Ca2+ within pools following InsP3-mediated Ca2+ release. Such changes in Ca2+ may be of great significance to the translation, translocation, and folding of proteins in ER, in particular with respect to the function of the now numerously described luminal Ca2+-sensitive chaperonin proteins. Studies have also focussed on the physiological role of pool Ca2+ changes with respect to cell growth. Emptying of pools using Ca2+ pump blockers can result in cells entering a stable quiescent G0-like growth state. After treatment with the irreversible pump blocker, thapsigargin, cells remain in this state until they are stimulated with essential fatty acids whereupon new pump protein is synthesized, functional Ca2+ pools return, and cells reenter the cell cycle. During the Ca2+ pool-depleted growth-arrested state, cells express a Ca2+ influx channel that is distinct from the store-operated Ca2+ influx channels activated after short-term depletion of Ca2+ pools. Overall, these studies indicate that significant changes in intraluminal ER Ca2+ do occur and that such changes appear linked to alteration of essential ER functions as well as to the cell cycle-state and the growth of cells.

POSSIBLE ROLE OF UTERINE CONTRACTIONS IN THE SHORT-TERM FLUCTUATIONS OF PLASMA ACTH CONCENTRATION IN FETAL SHEEP

1985 ◽  
Vol 106 (2) ◽  
pp. R9-R11 ◽  
Author(s):  
S.J. Lye ◽  
M.E. Wlodek ◽  
J.R.G. Challis
Keyword(s):  
Percentage Change ◽  
Plasma Acth ◽  
Short Term ◽  
Fetal Sheep ◽  
Uterine Activity ◽  
Fetal Plasma ◽  
Uterine Contractions ◽  
Intrauterine Pressure ◽  
Acth Concentration

ABSTRACT Uterine contractions, induced by the administration of oxytocin to sheep between d 123-144 of pregnancy, were associated with a mean transient decrease in fetal PaO2 of 2.8 mm Hg within 5 min. These changes were associated with a rapid increase in the concentration of ACTH in fetal plasma. There was a significant (P<0.05) increase in the percentage change (+40 to +47%) over basal ACTH levels in fetal plasma at +5, +15 and +20 min after oxytocin. Administration of saline had no significant effect on intrauterine pressure, fetal PaO2 or fetal plasma ACTH levels. We speculate that increases in uterine activity and/or transient decreases in fetal PaO2 may contribute to short-term fluctuations in plasma ACTH in fetal sheep.

Levels of pro-opiomelanocortin and prolactin mRNA in the fetal sheep pituitary following hypoxaemia and glucocorticoid treatment in late gestation

1995 ◽  
Vol 147 (1) ◽  
pp. 139-146 ◽  
Author(s):  
S G Matthews ◽  
J R G Challis
Keyword(s):  
Late Gestation ◽  
Pars Intermedia ◽  
Mrna Levels ◽  
Glucocorticoid Treatment ◽  
Fetal Sheep ◽  
Fetal Plasma ◽  
Pomc Mrna ◽  
Highly Sensitive ◽  
Ovine Fetal

Abstract It is well established that corticotrophin-releasing hormone and vasopressin can induce both synthesis and release of ACTH from the ovine pituitary gland, and that glucocorticoids can inhibit these responses. Changes in the abundance, localization and distribution of proopiomelanocortin (POMC) mRNA and prolactin (PRL) mRNA in the ovine fetal pituitary were examined by in situ hybridization following hypoxaemia applied in the presence or absence of concomitant cortisol in late gestation (day 135). Fetuses were distributed amongst four groups; saline-infused/normoxaemic, cortisol-infused/normoxaemic (0·3 mg/h), saline-infused/hypoxaemic and cortisol-infused/hypoxaemic. Hypoxaemia (6 h) was induced by reducing the maternal PaO2, resulting in a 6–8 mmHg decrease in fetal arterial PO2. Fetal infusions were commenced 5 h prior to and maintained throughout the treatment period. Hypoxaemia, which elevated fetal plasma ACTH and cortisol, caused a significant (P<0·05) increase in POMC mRNA in the pars distalis (PD), but was without effect on POMC mRNA in the pars intermedia (PI). Cortisol infusion attenuated the hypoxaemiainduced increase in POMC mRNA in the PD, but was without effect on non-stimulated steady-state POMC mRNA levels in either the PD or PI. PRL mRNA was only present in the PD and significantly (P<0·05) increased after cortisol infusion and hypoxaemia. In conclusion (i) POMC and PRL mRNA in the PD are increased following moderate hypoxaemia, (ii) cortisol attenuates changes in POMC mRNA but not PRL mRNA in the PD following hypoxaemia and (iii) cortisol increases PRL mRNA levels in the PD. Synthesis of POMC and PRL in the fetal PD is highly sensitive to homeostatic perturbations and glucocorticoids in late gestation. Journal of Endocrinology (1995) 147, 139–146

Sign in / Sign up

Export Citation Format

Share Document