The effect of fetal hypophysectomy with or without ACTH replacement on the molecular weight profile of enkephalin-containing peptides in the adrenal medulla of the fetal sheep

1992 ◽  
Vol 134 (3) ◽  
pp. 369-375 ◽  
Author(s):  
C. L. Coulter ◽  
I. R. Young ◽  
C. A. Browne ◽  
I. C. McMillen
Keyword(s):  
Molecular Weight ◽  
Adrenal Glands ◽  
Enzymatic Digestion ◽  
Late Gestation ◽  
Fetal Sheep ◽  
Carboxypeptidase B ◽  
Significant Difference ◽  
Group 5 ◽  
Pregnant Ewe

ABSTRACT We have investigated the possible role of the fetal pituitary and ACTH in the control of the synthesis and post-translational processing of the enkephalin precursor, proenkephalin A (proEnk A), in the fetal sheep adrenal gland in late gestation. Fetal hypophysectomy (n = 8) or sham operations (n = 4) were performed between 109 and 118 days of gestation. At 138–139 days, either ACTH(1–24) (10·5 μg/0·24 ml saline per h, n = 4) was infused intravenously for 72 h into hypophysectomized fetal sheep or 0·9% (w/v) NaCl alone (0·24 ml/h, n = 4) was infused for 72 h into hypophysectomized fetal sheep and sham-operated animals. At the end of the infusion the pregnant ewe was killed and left or right adrenal glands (n = 12) were collected from the fetal sheep that were intact and given saline (Intact + sal; n = 4), hypophysectomized and given saline (Hx + sal; n = 4) and hypophysectomized and given ACTH (Hx + ACTH; n = 4). Each adrenal was homogenized in acid (acetic acid (1 mol/l)/HCl (20 mmol/l)/2-mercaptoethanol (0·2%)). After centrifugation, the supernatant was loaded onto a Sephadex G-75 column (2·0 × 50 cm), eluted at 80 ml/24 h and fractions were collected (5 ml, n = 42). An aliquot of each fraction (2 ml) was dried down prior to enzymatic digestion (trypsin/carboxypeptidase B) and oxidation with H2O2, and assay for methionine-O-enkephalin (immunoreactive Met-O-Enk). The total adrenal content of immunoreactive Met-O-Enk was significantly greater in the Hx + ACTH group (326·2 ±66·7 (s.e.m.)ng/adrenal) when compared with either the Intact + sal group (152·7 ±44·0 ng/adrenal) or the Hx + sal group (112·1 ±20·8 ng/adrenal). In the adrenal glands from all fetuses immunoreactive Met-O-Enk was found in four molecular weight ranges: < 12 kDa, 12–7 kDa, 7–3 kDa and < 3 kDa. There was no significant difference between the Hx + sal and Hx + ACTH groups in the proportion of immunoreactive Met-O-Enk present in each of the molecular weight ranges in the adrenals and therefore the data from these groups were combined for further statistical analysis. The proportion of immunoreactive Met-O-Enk in the > 12 kDa range was significantly less in the Intact + sal group (5·5 ±2·3%) when compared with the hypophysectomized sheep with or without ACTH replacement (18·7 ± 4·5%). These data demonstrate that fetal hypophysectomy alters the molecular weight profile of Enk-containing peptides in the adrenal of the fetal sheep and whilst ACTH replacement in the hypophysectomized fetus does not alter the post-translational processing of the Enk-containing peptides, it stimulates an increase in the total amount of immunoreactive Met-O-Enk in the fetal adrenal in late gestation. Journal of Endocrinology (1992) 134, 369–375

Inhibin and follistatin concentrations in fetal tissues and fluids during gestation in sheep: evidence for activin in amniotic fluid

1994 ◽  
Vol 141 (2) ◽  
pp. 219-229 ◽  
Author(s):  
S Wongprasartsuk ◽  
G Jenkin ◽  
J R McFarlane ◽  
M Goodman ◽  
D M de Kretser
Keyword(s):  
Amniotic Fluid ◽  
Adrenal Glands ◽  
Late Gestation ◽  
Pituitary Cells ◽  
Fetal Sheep ◽  
Fetal Testis ◽  
Cells In Culture ◽  
Tissue Extracts ◽  
Significant Difference ◽  
The Individual

Abstract The concentrations of inhibin and follistatin in amniotic fluid and in tissue extracts from the placenta, gonads and adrenals of fetal sheep were measured using radioimmunoassays. These tissue extracts were from whole fetuses from days 16 to 45 and from the individual organs from day 46 to 145 (term) and were assayed at multiple dilutions. The capacity of these extracts to alter FSH production of rat anterior pituitary cells in culture was also assessed at multiple dilutions. Immunoactive inhibin concentrations in amniotic fluid from both sexes increased during gestation and levels were significantly greater in males than females. Peak concentrations of immunoreactive inhibin of 11·2±1·9 ng/ml were found in males at 116–125 days of gestation. Follistatin concentrations did not change throughout gestation and no significant difference was noted between sexes. Mean follistatin levels throughout gestation were 3·0±0·9 ng/ml for males and 3·7±0·9 ng/ml for females. Despite the potential for FSH inhibition by inhibin and follistatin, amniotic fluid from both sexes at all stages of gestation stimulated FSH secretion in the pituitary cell bioassays, suggesting the presence of activin which was confirmed by the measurement of immunoactive activin (13·3±2·5 ng/ml) in a specific radioimmunoassay. Maximum concentrations of immunoactive and bioactive inhibin in placental extracts were observed in late gestation (2·2 ±0·6 and 3·8±1·6 ng/g respectively) and there was no significant difference between sexes. Follistatin concentrations in placental cotyledons ranged from 11·5 to 27·1 ng/g with no significant difference between sexes. In view of the higher follistatin concentrations compared with inhibin, it is likely that the capacity of placental extracts to suppress FSH production by pituitary cells in culture is due predominantly to follistatin. Immunoactive inhibin was observed in high concentrations in the fetal testis throughout gestation; with concentrations increasing to a maximum of 1993·0± 519·7 ng/g at 126–135 days of gestation with a ratio of bioactive: immunoactive inhibin of 1:20. Although bioactive and immunoactive inhibin was also observed in fetal ovaries and adrenals from both male and female fetuses, concentrations were lower than those observed in fetal testes. Follistatin concentrations in the fetal testis were elevated between 70 and 95 days (97·6 ng/g) and then declined. Similar concentrations were found in the adrenal glands of both sexes (males 83·5–103·3 ng/g: females 55·3–95·8 ng/g). In both males and females, immunoactive inhibin concentrations in fetal adrenals increased during gestation peaking at levels of 34·4±16·5 and 27·8± 9·0 ng/g respectively. These data suggest that the capacity of adrenal extracts to suppress FSH production by pituitary cells is due to both inhibin and follistatin. These studies demonstrated that significant concentrations of immunoactive inhibin and follistatin are present in amniotic fluid, and the fetal gonads, adrenal glands and placenta in sheep. The role of these proteins during fetal development requires further study. Journal of Endocrinology (1994) 141, 219–229

The adrenocorticotropic hormone and arginine vasopressin responses to hypercapnia in fetal and maternal sheep

1993 ◽  
Vol 264 (2) ◽  
pp. R324-R330 ◽  
Author(s):  
H. G. Chen ◽  
C. E. Wood
Keyword(s):  
Arginine Vasopressin ◽  
Adrenocorticotropic Hormone ◽  
Fetal Sheep ◽  
Arterial Pco2 ◽  
Fetal Plasma ◽  
Arterial Blood ◽  
Arterial Ph ◽  
Bilateral Vagotomy ◽  
Pregnant Ewe

Previous studies have demonstrated that fetal adrenocorticotropic hormone (ACTH) and arginine vasopressin (AVP) are increased during periods of acidemia produced by infusion of acid intravenously or by acidemia secondary to hypovolemia. The purpose of this study was to quantify ACTH and AVP responses to hypercapnic acidemia and to test the role of the peripheral chemoreceptors in the control of these responses. Chronically catheterized fetal sheep were subjected to carotid sinus denervation and bilateral vagotomy or were studied intact. At least 5 days after surgery, fetuses were exposed to a 60-min period of normocapnia or hypercapnia, delivered via a polyethylene bag containing 5-8% CO2 in 21% O2 fitted over the head of the pregnant ewe. Hypercapnia significantly increased fetal arterial PCO2 to 55.2 +/- 1.8 and 55.9 +/- 2.2 mmHg and decreased arterial pH to 7.257 +/- 0.011 and 7.281 +/- 0.010 in intact and denervated fetuses, respectively. Fetal mean arterial blood pressure was decreased slightly in the denervated fetuses during hypercapnia. Fetal plasma AVP was increased in both groups equally, and plasma ACTH and cortisol were increased in the denervated fetuses only. Fetal heart rate was increased significantly in intact but not denervated fetuses. We conclude that respiratory acidemia is a mild stimulus to AVP secretion and that this response is not attenuated by peripheral chemodenervation.

scholarly journals Effects of thyroid hormones on pulmonary and renal angiotensin-converting enzyme concentrations in fetal sheep near term

2002 ◽  
Vol 173 (1) ◽  
pp. 143-150 ◽  
Author(s):  
AJ Forhead ◽  
AL Fowden
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Thyroid Hormones ◽  
Plasma Cortisol ◽  
Experimental Manipulation ◽  
Late Gestation ◽  
Converting Enzyme ◽  
Fetal Sheep ◽  
Near Term ◽  
Sheep Fetus

In the sheep fetus, pulmonary and renal concentrations of angiotensin-converting enzyme (ACE) increase towards term in parallel with the prepartum surges in plasma cortisol and tri-iodothyronine (T(3)). The ontogenic change in pulmonary ACE has been shown to be induced, at least in part, by cortisol but the role of the thyroid hormones is unknown. Therefore, this study investigated the effects of thyroid hormones on tissue ACE concentration in fetal sheep during late gestation. Pulmonary and renal ACE concentrations were measured in sheep fetuses after experimental manipulation of thyroid hormone status by fetal thyroidectomy and exogenous hormone infusion. In intact fetuses, pulmonary and renal ACE concentrations increased between 127-132 and 142-145 days of gestation (term 145 +/- 2 days), coincident with the prepartum rises in plasma cortisol and T(3). The ontogenic increment in pulmonary ACE concentration was abolished when the prepartum surge in T(3), but not cortisol, was prevented by fetal thyroidectomy. At 143-145 days, ACE concentration in the lungs and kidneys of the thyroidectomised fetuses were both lower than those in the intact fetuses. In intact fetuses at 127-132 days, pulmonary ACE was upregulated by intravenous infusions of either cortisol (2-3 mg/kg per day) or T(3) (8-12 microg/kg per day) for 5 days. Renal ACE was unaffected by cortisol or T(3) infusion. Therefore, thyroid hormones have an important role in the developmental control of pulmonary and renal ACE concentration in the sheep fetus towards term. In addition, the prepartum rise in plasma T(3) appears to mediate, in part, the maturational effect of cortisol on pulmonary ACE concentration.

Changes in blood flow distribution during the perinatal period in fetal sheep and lambs

1992 ◽  
Vol 70 (12) ◽  
pp. 1576-1582 ◽  
Author(s):  
Michelle P. Bendeck ◽  
B. Lowell Langille
Keyword(s):  
Blood Flow ◽  
Adrenal Glands ◽  
Flow Distribution ◽  
Perinatal Period ◽  
Tissue Growth ◽  
Late Gestation ◽  
Blood Flow Distribution ◽  
Total Blood ◽  
Fetal Sheep ◽  
Blood Flows

We have measured total blood flows and blood flows per 100 g tissue to major tissues at 120 and 140 days gestation in fetal sheep and at 3 and 21 days of age in lambs (gestation period = 144 ± 2 days). Between 120 and 140 days gestation, flow per 100 g tissue increased by 74, 150, and 317% in the renal, intestinal, and hepatic arterial beds, but no further significant change in flow was observed at 3 or 21 days postpartum. Blood flows per 100 g to cerebral hemispheres and cerebellar tissues also increased dramatically during late gestation (142 and 121%, respectively), but declined sharply by 3 days postpartum (73 and 75%, respectively). Brain blood flows at 21 days postpartum remained substantially below late gestational levels. Adrenal blood flows per 100 g more than doubled during late gestation, fell by more than half at birth, and only partially recovered by 21 days of age. Blood flows to carcass tissues did not change in late gestation, fell at birth, then partially recovered. Pre- and post-natal increases in brain blood flows were almost entirely attributable to increased perfusion rather than tissue growth, whereas large perinatal increases in flow to the diaphragm paralleled tissue growth. Tissue growth and increased perfusion per 100 g contributed almost equally to increased blood flows to kidneys postnatally, and to adrenal glands and the gastrointestinal tract prenatally.Key words: blood flow, perinatal, birth, fetus, sheep.

scholarly journals Exogenous GH infusion to late-gestational fetal sheep does not alter fetal growth and metabolism

2000 ◽  
Vol 166 (3) ◽  
pp. 591-597 ◽  
Author(s):  
MK Bauer ◽  
JE Harding ◽  
BH Breier ◽  
PD Gluckman
Keyword(s):  
Fetal Growth ◽  
Growth Increment ◽  
Late Gestation ◽  
Placental Lactogen ◽  
Maternal Weight ◽  
Gh Treatment ◽  
Fetal Sheep ◽  
Crown Rump Length ◽  
Gh Secretion ◽  
Significant Difference

The role of GH in the regulation of fetal growth and metabolism in late gestation is not well defined. The aim of this study was to determine the effects of exogenous GH infusion on fetal growth and feto-placental metabolism in the normally growing late-gestation fetal sheep. Eleven fetuses received pulsatile GH infusion (3.5 mg/day) for 10 days while 12 control fetuses received vehicle. The GH infusion was given as a continuous infusion (2.5 mg/day) plus an additional pulsatile component (30 pulses equivalent to 1 mg/day) designed to mimic the natural pattern of GH secretion. Fetal GH infusion raised the circulating fetal concentrations of GH threefold, but did not change fetal concentrations of IGF-I, IGF-binding protein-3, insulin or ovine placental lactogen. GH-treated fetuses had blood urea concentrations 15% lower than controls (P<0.05) and glucose uptake 18% lower per kg fetal weig! ht (P=0.06). There were no other differences attributable to fetal GH infusion in feto-placental metabolism, placental function or placental blood flow. GH-treated fetuses were larger than controls at postmortem (weight+13%, P<0.01; girth+5%, P<0.01; crown-rump length+3%, P<0.05). However, there were no differences between groups in measures of fetal growth (increment in chest girth and hindlimb length). GH-treated fetuses had heavier mothers and when maternal weight was included as a covariate in the analysis, there was no significant difference between treatment groups that could be attributed to GH treatment. GH infusion to normal fetal sheep does not appear to have a significant effect on feto-placental metabolism or fetal growth.

Arginine vasopressin responses to hypoxia and hypercapnia in late-gestation fetal sheep

1991 ◽  
Vol 260 (6) ◽  
pp. R1077-R1081 ◽  
Author(s):  
H. Raff ◽  
C. W. Kane ◽  
C. E. Wood
Keyword(s):  
Arginine Vasopressin ◽  
Late Gestation ◽  
Fetal Sheep ◽  
Fetal Plasma ◽  
Hypoxic Conditions ◽  
Arterial Ph ◽  
Hypercapnic Hypoxia ◽  
Per Se ◽  
Peripheral Arterial

The purpose of this study was to determine the interaction of hypoxia and hypercapnia in the control of arginine vasopressin (AVP) secretion in fetal sheep and to determine the role of the peripheral arterial chemoreceptors in that response. We measured the plasma AVP response to hypercapnia and/or hypoxia in catheterized intact or sinoaortic-denervated fetal sheep between 123 and 144 days of gestation. Ewes were exposed to the following inspired gases: two successive 30-min periods of normocapnic normoxia, 30 min of normocapnic normoxia followed by 30 min of normocapnic hypoxia, two successive 30-min periods of hypercapnic normoxia, or 30 min of hypercapnic normoxia followed by 30 min of hypercapnic hypoxia (i.e., asphyxia). Hypercapnia per se had no significant effect on fetal plasma AVP. Normocapnic hypoxia per se resulted in a significant increase in fetal plasma AVP. Although hypercapnia resulted in a significant acidemia, the decrease in arterial pH was more marked under hypoxic conditions. Hypercapnia/acidemia augmented the AVP response to hypoxia. Fetal sinoaortic denervation did not significantly attenuate any of the AVP responses. We conclude that hypercapnia augments the fetal AVP response to hypoxia and that the AVP response to neither normocapnic nor hypercapnic hypoxia is dependent on afferent information carried in the carotid sinus or aortic nerves.

Maternal pinealectomy alters the daily pattern of fetal breathing in sheep

1990 ◽  
Vol 258 (1) ◽  
pp. R284-R287 ◽  
Author(s):  
I. C. McMillen ◽  
R. Nowak ◽  
D. W. Walker ◽  
I. R. Young
Keyword(s):  
Time Of Day ◽  
Behavioral Pattern ◽  
Late Gestation ◽  
Once Daily ◽  
Daily Pattern ◽  
Significant Difference ◽  
Fetal Breathing ◽  
Fetal Breathing Movements ◽  
The Mean ◽  
Pregnant Ewe

We have investigated the effect of pinealectomy of the pregnant ewe on the 24-h pattern of fetal breathing activity during late gestation. Fetal breathing movements were recorded during 24-h periods on 18 occasions in 5 pinealectomized ewes and on 24 occasions in 6 pineal-intact ewes between 120 and 145 days gestation. All ewes were fed once daily between 1000 and 1300 h and were kept under a light-dark cycle 12:12 h. There was no significant difference in the mean hourly incidence of fetal breathing movements between the pineal-intact (27.2 +/- 0.5 min/h) and pinealectomized (25.5 +/- 0.6 min/h) groups. However, there was a significant difference in the 24-h profiles of fetal breathing movements in the two groups. The peak incidence of fetal breathing occurred between 1900 and 2000 h in the pineal-intact ewes and between 1200 and 1300 h in the pinealectomized ewes. We conclude that maternal pinealectomy alters the daily pattern of a fetal behavioral pattern and that maternal melatonin may therefore provide the fetus with information about time of day.

Ontogeny and effect of cortisol on vasopressin-1b receptor expression in anterior pituitaries of fetal sheep

2003 ◽  
Vol 284 (1) ◽  
pp. R51-R56 ◽  
Author(s):  
Sharla F. Young ◽  
Jennifer L. Smith ◽  
Jorge P. Figueroa ◽  
James C. Rose
Keyword(s):  
Receptor Expression ◽  
Late Gestation ◽  
Mrna Levels ◽  
Fetal Sheep ◽  
Fetal Plasma ◽  
Protein Levels ◽  
Receptor Mrna ◽  
Naturally Occurring ◽  
V1b Receptor

Corticotroph responsiveness to arginine vasopressin (AVP) increases during late gestation in fetal sheep. The mechanism of this increase in AVP responsiveness is currently unknown but could be related to an increase in vasopressin type 1b (V1b) receptor expression in the pituitary during development. To determine if there are ontogenic changes in V1b receptor expression that may help explain the changes in ACTH responses to AVP, we studied pituitaries from three groups of fetal sheep [100, 120, or 140 days gestational age (dGA)]. V1b receptor mRNA and protein significantly decreased by 140 dGA. Peak V1b mRNA levels were detected at 100 dGA, while peak V1b protein levels were detected at 120 dGA. The reduction in V1b receptor expression in late gestation may be due to the naturally occurring peripartum increase in fetal plasma cortisol because cortisol infusion at 122–130 dGA decreased V1b receptor mRNA. Thus there is a marked decrease in the expression of the V1b receptor in the pituitary during fetal development, leaving the role of the V1b receptor in increasing AVP responsiveness uncertain.

Proopiomelanocortin, prolactin and growth hormone messenger ribonucleic acid levels in the fetal sheep pituitary during late gestation

1993 ◽  
Vol 129 (3) ◽  
pp. 263-267 ◽  
Author(s):  
Jennifer J Merei ◽  
Alix Rao ◽  
lain J Clarke ◽  
I Caroline McMillen
Keyword(s):  
Growth Hormone ◽  
Ribonucleic Acid ◽  
Late Gestation ◽  
Mrna Levels ◽  
Fetal Sheep ◽  
Messenger Ribonucleic Acid ◽  
Pomc Mrna ◽  
Significant Difference ◽  
The Mean ◽  
Pomc Gene

We have measured the relative levels of proopiomelanocortin (POMC), prolactin (PRL) and growth hormone (GH) messenger ribonucleic acid (mRNA) in the anterior and neurointermediate lobes of the fetal pituitary during the last 2–3 weeks of gestation. The mean POMC mRNA/18S RNA ratio in the fetal anterior pituitary was significantly greater (p<0.02) at 130–136 days (0.90±0.08; N=9) than at 141–143 days of gestation (0.67±0.07; N=6). In contrast, the mean PRL mRNA/18S RNA ratio increased significantly (p< 0.02) ) between 130 and 136 days (0.31±0.05; N = 9) when compared with 141–143 days of gestation (0.58±0.10; N = 6). There was no significant difference, however, between the mean GH mRNA/18S RNA ratio in fetal anterior pituitaries at 130–136 days (0.95±0.04; N = 9) when compared with 141–143 days of gestation (1.08±0.14; N=6). The POMC mRNA/18S RNA ratio in the neurointermediate lobes was seven-, five- and tenfold higher than in anterior pituitaries at 130–134, 135–136 and 141–143 days of gestation, respectively. We hypothesize that elevated circulating cortisol levels after 140 days of gestation act in the slow time domain (i.e. over days) to suppress POMC gene expression and that the increase in fetal pituitary PRL mRNA levels may be a consequence of oestrogen stimulation in late gestation.

Differential association of endogenous proenkephalin-derived peptides with membranes of microsomes from rat striatum, adrenal medulla and heart ventricle

1990 ◽  
Vol 5 (2) ◽  
pp. 175-183 ◽  
Author(s):  
O. Vindrola ◽  
A. Ase ◽  
R. Aloyz ◽  
F. Saravia ◽  
S. Finkielman ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Adrenal Medulla ◽  
Secretory Granules ◽  
Enzymatic Digestion ◽  
Rat Striatum ◽  
Heart Ventricle ◽  
Carboxypeptidase B ◽  
Molecular Weights ◽  
Chromatographic Profile ◽  
Microsomal Membranes

ABSTRACT Proenkephalin-derived peptides, in common with other prohormones, are associated with membranes of microsomes and secretory granules in the bovine adrenal medulla. Post-translational processing of the precursor molecule varies depending upon the tissue. The relationship between post-translational events in different tissues was examined by studying the membrane association of endogenous proenkephalin-derived peptides in the crude microsomal fraction of rat adrenal medulla, brain striatum and heart ventricle. [Met]-Enkephalin and synenkephalin (proenkephalin(1–70)) immunoreactivities were quantified by radioimmunoassay after sequential enzymatic digestion with trypsin and carboxypeptidase B. Between 60 and 75% of total immunoreactive peptides present in intact microsomes of the three tissues were associated with membranes and specifically released with 2 m KSCN (pH 7·4). Analysis of the chromatographic profile of materials present in the soluble and associated fractions produced the following results. In the three tissues the materials associated with microsomal membranes corresponded to peptides larger than 3–5 kDa and displayed synenkephalin and [Met]-enkephalin immunoreactivity. Adrenal and heart microsomes showed a continuous pattern of membrane-associated proenkephalin-derived peptides of high, intermediate and low molecular weights containing the synenkephalin and [Met]-enkephalin sequences. These tissues, however, presented quantitative differences, as the highest concentrations belonged to materials larger and smaller than 12·5 kDa in adrenal and heart microsomes respectively. On the other hand, brain striatal microsomes displayed a discontinuous pattern of associated materials, with the absence of some products of high and intermediate molecular weight. Only in the soluble fraction of striatal microsomes were peptides detected of high and intermediate molecular weight containing the [Met]-enkephalin but not the synenkephalin sequence. In conclusion, this study demonstrates that the association of proenkephalin-derived peptides with microsomal membranes is a common event in the adrenal medulla, heart ventricle and rat striatum, involving, in all cases, some portion of the C-terminal sequence of the synenkephalin molecule. These observations provide further evidence suggesting that the differential profiles of proenkephalin-derived peptides in the adrenal medulla and striatum may be related to differential post-translational processing instead of changes in processing rate.

Sign in / Sign up

Export Citation Format

Share Document