Differential regulation of pro-opiomelanocortin mRNA in the pars distalis and pars intermedia of the pituitary gland with repetitive umbilical cord occlusion in preterm fetal sheep

1998 ◽  
Vol 5 (1) ◽  
pp. 162A-162A
Author(s):  
L GREEN ◽  
M FRASER ◽  
J HOMAN ◽  
B RICHARDSON ◽  
J CHALLIS
Keyword(s):  
Pituitary Gland ◽  
Umbilical Cord ◽  
Differential Regulation ◽  
Pars Intermedia ◽  
Pars Distalis ◽  
Fetal Sheep

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.

ADRENOCORTICOTROPHIC HORMONE IN THE ANTERIOR AND NEUROINTERMEDIATE LOBES OF THE FETAL RAT PITUITARY GLAND

1981 ◽  
Vol 89 (2) ◽  
pp. 181-186 ◽  
Author(s):  
ALAIN CHATELAIN ◽  
J. P. DUPOUY
Keyword(s):  
Pituitary Gland ◽  
Functional Differentiation ◽  
Pars Intermedia ◽  
Adrenocorticotrophic Hormone ◽  
Pars Distalis ◽  
Adult Rats ◽  
Adrenal Cells ◽  
Specific Radioimmunoassay ◽  
Fetal Rat ◽  
Rat Pituitary

The concentration of ACTH in the pars distalis and pars intermedia of the fetal rat hypophysis from days 17–21 of pregnancy was measured with a specific radioimmunoassay and a bioassay using isolated adrenal cells from adult rats. In both lobes of the pituitary gland, a significant correlation was observed between immunoreactive and bioreactive values, expressed as pg equivalents synthetic human 1–39 ACTH per μg protein. In the pars distalis, ACTH concentrations increased steadily from days 17–20 and then remained unchanged to term. At this time they were tenfold higher than on day 17. In the neurointermediate lobe, ACTH was detected only from day 18; the concentration of ACTH increasing between days 18 and 19. At each of the stages of pregnancy examined, the concentration of ACTH in the pars distalis was greater than that in the pars intermedia. These data have demonstrated that ACTH is present in both anterior and neurointermediate lobes of the fetal rat hypophysis, that the functional differentiation of the pars distalis takes place earlier than that of the pars intermedia, and that the concentrations of corticotrophin in the pars distalis and in the pars intermedia have different patterns of development as gestation progresses.

Expression, distribution, regulation and function of IGFs in the ovine fetal pituitary

1995 ◽  
Vol 14 (3) ◽  
pp. 323-336 ◽  
Author(s):  
F Lü ◽  
K Yang ◽  
V K M Han ◽  
J R G Challis
Keyword(s):  
Pituitary Gland ◽  
Endocrine Cells ◽  
Cell Types ◽  
Pars Intermedia ◽  
Pars Distalis ◽  
Paracrine Factors ◽  
Pomc Mrna ◽  
Pars Nervosa ◽  
Igf I ◽  
And Function

ABSTRACT Activation of the fetal pituitary-adrenal axis is crucial for fetal organ maturation and the onset of parturition in sheep. Many factors including corticotrophin-releasing hormone (CRH) and arginine vasopressin secreted from the hypothalamus, and growth factors produced within the pituitary may be involved in the regulation of maturation of the fetal pituitary gland. IGFs have mitogenic and differentiation-promoting capacities in a variety of organs and are synthesized as paracrine factors within developing tissues. However, there is little information concerning the synthesis, distribution, regulation and function of IGFs in the fetal pituitary gland at different times during pregnancy. Therefore, we have localized IGF-I and IGF-II mRNAs and peptides, and determined the effect of cortisol on the level of IGF-II mRNAs in the pituitary glands of developing sheep fetuses. We examined the possible effects of IGFs on corticotroph function in cultures of adenohypophysial cells from term fetuses. Seven species of IGF-II transcripts of 1·2–6·0 kb were identified by Northern blot analysis in the pituitary gland of fetuses between day 60 of gestation and term (day 145). The levels of IGF-II mRNAs did not change significantly during pregnancy, although there was a trend for the presence of higher levels of IGF-II mRNAs at day 60 of gestation. IGF-I mRNA was not detectable. By in situ hybridization, IGF-II mRNA was localized to non-endocrine cells and to cells lining the blood vessels of the pars distalis, to some presumed endocrine cells in the pars distalis and pars intermedia, and to clusters of cells in the pars nervosa. In contrast, IGF-I and IGF-II peptides were detected in the presumed endocrine cells in the pars distalis and pars intermedia but not in the pars nervosa. Incubation of adenohypophysial cells from term fetuses with IGF-I, but not IGF-II, for 48 h increased specific 125I-Tyr-ovine CRH binding. However, neither IGF-I nor IGF-II had any significant effects on the basal or CRH-stimulated immunoreactive (ir)-ACTH output, the level of POMC mRNA or the number of ir-ACTH positive cells. Infusion of cortisol to fetuses starting at day 96 of gestation for 100 h or at days 120–125 of gestation for 84 h did not affect the level of IGF-II mRNAs in the pars distalis but decreased the levels of POMC mRNA. These results are consistent with IGFs having the potential to influence fetal pituitary function, although probably on cell types other than the corticotrophs. The likely sources of IGFs may be predominantly local (IGF-II) or from extrapituitary sources (IGF-I).

scholarly journals Identification of beta-endorphins in the pituitary gland and blood plasma of the common carp (Cyprinus carpio)

2001 ◽  
Vol 169 (2) ◽  
pp. 271-280 ◽  
Author(s):  
EH van Den Burg ◽  
RJ Arends ◽  
B Devreese ◽  
I Vandenberghe ◽  
J Van Beeumen ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Cyprinus Carpio ◽  
Pars Intermedia ◽  
Pars Distalis ◽  
Beta Endorphin ◽  
Common Carp Cyprinus Carpio ◽  
Carp Cyprinus Carpio ◽  
The Common ◽  
Beta Endorphins

Carp beta-endorphin is posttranslationally modified by N-terminal acetylation and C-terminal cleavage. These processes determine the biological activity of the beta-endorphins. Forms of beta-endorphin were identified in the pars intermedia and the pars distalis of the pituitary gland of the common carp (Cyprinus carpio), as well as the forms released in vitro and into the blood. After separation and quantitation by high performance liquid chromatography (HPLC) coupled with radioimmunoassay, the beta-endorphin immunoreactive products were identified by electrospray ionisation mass spectrometry and peptide sequencing. The release of beta-endorphins by the pituitary gland was studied after stimulation with corticotrophin-releasing factor (CRF) in vitro. In the pars intermedia, eight N-acetylated truncated forms were identified. Full length N-acetyl beta-endorphin(1-33) coeluted with N-acetyl beta-endorphin(1-29) and these forms together amounted to over 50% of total immunoreactivity. These products were partially processed to N-acetyl betaendorphin(1-15) (30.8% of total immunoreactivity) and N-acetyl beta-endorphin(1-10) (3.1%) via two different cleavage pathways. The acetylated carp homologues of mammalian alpha- and gamma-endorphin were also found. N-acetyl beta-endorphin(1-15) and (1-29) and/or (1-33) were the major products to be released in vitro, and were the only acetylated beta-endorphins found in blood plasma, although never together. CRF stimulated the release of opioid beta-endorphin from the pars distalis. This non-acetylated beta-endorphin represents the full length peptide and is the most abundant form in plasma.

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.

Evolution of the Brain–Pituitary Relationship: Evidence from the Agnatha

1980 ◽  
Vol 37 (11) ◽  
pp. 1680-1686 ◽  
Author(s):  
Aubrey Gorbman
Keyword(s):  
Connective Tissue ◽  
Pituitary Gland ◽  
Petromyzon Marinus ◽  
Neurosecretory Cells ◽  
Pars Intermedia ◽  
Pars Distalis ◽  
Vascular Connection ◽  
Anatomical Relationship ◽  
Nervous Connection ◽  
The Brain

In the brain of the lamprey there are neurosecretory cells that manufacture and carry known hormonal materials to the neurohypophysis, which is that part of the diencephalic floor that is adjacent to the adenohypophysis. The adenohypophysis is differentiated into a pars distalis and a pars intermedia. However, unlike all other vertebrates, there is no vascular or nervous connection between the neurohypophysis and the pars distalis. If there is any regulation of the adenohypophysis by the hormones released from the endings of neurosecretory axones in the neurohypophysis, it would have to be by diffusion across the intervening connective tissue. Such regulation remains to be demonstrated.It is difficult to decide whether this relationship between neurohypophysis and pars distalis in the lamprey (and hagfish) is primitive or degenerate in its evolution. However, in three groups of more primitive fishes an intermediate condition is found in which a vascular connection exists between the neurohypophysis and a part of the adenohypophysis. This being so, we may speculate that the lamprey and other cyclostomes represent the simplest and most primitive anatomical relationship between brain and adenohypophysis, one in which the two organs are merely apposed, allowing neurosecretions to diffuse between the two. In the elasmobranchs, holocephalians, and the coelacanth, part of the pars distalis has been vascularized by portal vessels beginning in the neurohypophysis. In all other vertebrates the entire pars distalis is so vascularized.Key words: brain, pituitary gland, neurosecretion, hormones, evolution, Lampetra richardsoni, L. tridentata, Petromyzon marinus

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