Biomedical subjects

E T Berdusco

Publications and source records attributed to E T Berdusco.

12 recordsLinked to original sources

PubMed1997

Immunolocalisation of P450(C17) in the fetal sheep adrenal gland during gestation and in response to ACTH and glucocorticoid administration.

In sheep, increased output of cortisol from the fetal adrenal gland is critical to organ maturation and parturition. Cortisol synthesis is determined in part by the activity of P450(C17) enzyme. We have used immunohistochemistry and Western immunoblotting to examine the distribution of P450(C17) in the ovine fetal adrenal during gestation, and after ACTH or dexamethasone administration to fetuses between Days 125 and 130. The patterns were compared with changes in 3beta-hydroxysteroid dehydrogenase (3beta-HSD) localisation and levels. Adrenal tissue was obtained from four fetuses at each of Days 63-65, 100, 125-130 and term (>140 days). Further animals were chronically catheterised and infused with ACTH, dexamethasone or saline for 96 h beginning on Day 125. Immunohistochemistry for P450(C17), 3beta-HSD, and phenylethanolamine-N-methyl transferase (PNMT) was conducted using standard techniques. At Day 63-65 of pregnancy immunoreactive (ir-)P450(C17) was present in cords of cells throughout the adrenal gland. Ir-P450(C17) was reduced or was undetectable at Day 100, but had increased by Day 125-130, and was present throughout the zona fasciculata of the adrenal cortex of term animals. An increase in P450(C17) protein was also seen between Day 100 and 125 by Western blotting, and after ACTH treatment. Dexamethasone administration led to a marked reduction in ir-P450(C17) levels. In contrast, ir-3beta-HSD was present in the fetal adrenal cortex between Day 100 and term, and was less affected by ACTH or dexamethasone treatment. We conclude that P450(C17) in the fetal sheep adrenal is responsive to regulation by ACTH, and that changes in its levels correlate with previously reported alterations in patterns of cortisol output by the fetal adrenal gland.

3-Hydroxysteroid Dehydrogenases↗

PubMed1995

Corticosteroid-binding globulin (CBG) in fetal development.

In fetal sheep the prepartum increase in plasma cortisol concentration is associated with an increase in high affinity corticosteroid binding activity in plasma. This appears to reflect an increase in corticosteroid-binding globulin (CBG) biosynthesis from the fetal liver, and evidence is presented that hepatic CBG gene expression is increased by exposure to glucocorticoids in the fetus. Immunoreactive CBG is found in other fetal tissues, and CBG mRNA is present in fetal pituitary. CBG reduces the ability of cortisol to exert negative feedback on basal or CRH-stimulated ACTH output by fetal sheep pituitary cells in culture. We suggest that CBG interacts with cortisol in a manner that maintains a low negative feedback on the pituitary, and perhaps hypothalamus. This constitutes a component of the cascade of events that is associated with hypothalamic-pituitary-adrenal activation in the late gestation fetus, and with the onset of parturition.

Animals↗

PubMed1995

Effects of incremental cortisol and adrenalectomy on plasma corticosteroid binding capacity in fetal sheep.

The effects of incremental cortisol infusion or fetal adrenalectomy on plasma corticosteroid-binding capacity (CBC) were examined in sheep fetuses during late gestation (term approximately 150 days). Cortisol, infused from day 120 at 1.5 mg/day for the first 3 days, 2.5 mg/day for the next 5 days, and 3.5 mg/day for the final 2 days, stimulated a significant rise in plasma CBC and immunoreactive corticosteroid binding globulin (CBG). There was a significant positive correlation between individual values for total plasma cortisol concentrations and CBC values. In contrast, fetal adrenalectomy at day 115 prevented the rise in plasma CBC found in intact fetuses at term. These experiments show that exogenous cortisol, given in a manner that mimics the prepartum rise in fetal plasma cortisol, stimulates CBG biosynthesis, whereas abolition of the cortisol rise prevents the increase in CBG. The study provides strong support for the proposal that the prepartum increase in CBG biosynthesis in fetal sheep occurs in response to the progressive rise in adrenal cortisol output by the fetus towards term.

Adrenal Cortex Hormones↗

PubMed1995

Corticosteroid-binding globulin (CBG) production by hepatic and extra-hepatic sites in the ovine fetus; effects of CBG on glucocorticoid negative feedback on pituitary cells in vitro.

Plasma cortisol levels increase in fetal sheep during late gestation and this is associated with an increase in plasma corticosteroid-binding globulin (CBG) concentrations. However, the relative tissue sources of plasma CBG, the ontogeny of its biosynthesis and glycoform composition have not been established in the ovine fetus. Therefore we examined whether changes in plasma corticosteroid binding capacity (CBC) in fetal sheep during late gestation were associated with different patterns of glycosylation and reflected changes in tissue CBG expression. Since free cortisol is considered the bioactive fraction, we measured changes in the percent and absolute free cortisol in fetal plasma during late gestation. In order to examine whether CBG alters cortisol negative feedback at the level of the fetal pituitary, we also examined the effect of exogenous CBG in mediating the glucocorticoid-induced suppression of basal and corticotrophin-releasing hormone (CRH)-stimulated ACTH release from fetal pituitary cells in culture. The mean free cortisol concentration in plasma was not different between days 15 and 20 prior to parturition, and between 5 and 10 days prepartum, although it did rise between these times. Plasma CBC in chronically catheterized fetuses rose from 23.3 +/- 4.6 ng/ml at day 115 to 86.5 +/- 20.8 ng/ml at term and then decreased rapidly after birth. Between day 125 and day 140 of pregnancy approximately 10% of fetal plasma CBG was retarded by Concanavalin-A chromatography. This proportion increased at birth and attained adult values of > 70% by one month of age. By Northern blotting the relative levels of CBG mRNA in the fetal liver did not change between days 100 and 125, then increased significantly at day 140, but declined at term and in newborn lambs. CBG mRNA was undetectable in total RNA from lung, kidney, hypothalamus and placentomes, but was present in the fetal pituitary at days 125 and 140. Reverse transcription-PCR was used to confirm the presence of CBG mRNA in pituitary tissue from term fetuses. In cultures of term fetal pituitary cells, added CBG attenuated the cortisol- but not the dexamethasone-mediated suppression of basal and CRH-stimulated ACTH release. We conclude that in fetal sheep there is an increase in the corticosteroid binding capacity of plasma during late pregnancy which regulates, in part, free cortisol levels in the circulation. The liver is the major site of CBG biosynthesis in the fetus and at least until day 140 of gestation the rise in plasma CBC is associated with an increase in hepatic CBG mRNA levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗

PubMed1994

Regulation of insulin-like growth factor-II gene expression in the ovine fetal adrenal gland by adrenocorticotropic hormone and cortisol.

Maturation and activation of the fetal adrenal gland is crucial to fetal organ maturation and the onset of parturition in sheep. Insulin-like growth factors (IGFs) have been demonstrated to promote fetal adrenal mitogenesis and steroidogenesis in some species. Our previous studies showed that IGF-II mRNA is expressed in the steroidogenic cells of the fetal sheep adrenal, suggesting that IGF-II may be an important regulator of fetal adrenal function. However, the regulation of IGF-II gene expression is poorly understood. In the present study we measured the changes in IGF-II mRNA level in fetal sheep adrenals during late gestation in response to ACTH and cortisol. Either saline (0.5 ml/h) or cortisol (1 mg/24 h) was infused for 100 h to fetal sheep beginning on day 95 or 96 of pregnancy, or saline (0.5 ml/h), ACTH (0.5 micrograms/h) or cortisol (1 mg/h) was infused for 84 h to fetal sheep beginning on days 120-125 of pregnancy (term = 145 days). Adrenal RNA was subjected to Northern blot analysis with an ovine IGF-II cDNA probe. The relative abundance of total IGF-II mRNA decreased significantly in the ACTH- and cortisol-treated fetuses. IGF-II mRNA was localized by in situ hybridization using a 35S-labeled antisense ovine IGF-II cRNA probe, and IGF-II peptide was localized by immunohistochemistry. There were no differences in the cellular distribution patterns of IGF-II mRNA and IGF-II peptide after treatments, but the intensity of the hybridization signal for IGF-II mRNA and of immunostaining for IGF-II peptide decreased in adrenals from fetuses treated with ACTH or cortisol. These results suggest that ACTH and cortisol decrease IGF-II gene expression in the ovine fetal adrenal. We speculate that the cortisol surge observed in the late gestation ovine fetus may be responsible for down-regulation of IGF-II gene expression in the fetal adrenal at or just before birth.

Adrenal Glands↗

PubMed1994

Low-dose cortisol infusion increases plasma corticosteroid-binding globulin (CBG) and the amount of hepatic CBG mRNA in fetal sheep on day 100 of gestation.

Synthetic glucocorticoids stimulate the production of corticosteroid-binding globulin (CBG) by the liver of the sheep fetus near term (day 145). We have examined whether physiological changes in plasma cortisol alter plasma CBG concentrations, patterns of glycosylation and the amount of hepatic CBG mRNA at earlier times during pregnancy (day 100), prior to the activation of fetal hypothalamic-pituitary-adrenal function. Cortisol was infused into chronically catheterized sheep fetuses in amounts that raised the plasma cortisol concentration by about 15 nmol/l. This treatment resulted in a significant increase in the plasma corticosteroid-binding capacity and in the amount of CBG mRNA in the fetal liver, but did not alter the proportion of CBG retained using Concanavalin A chromatography. We conclude that the CBG gene in the liver of fetal sheep responds to physiological changes in plasma concentration of cortisol and we speculate that the rise in plasma CBG concentration is important in diminishing the negative feedback effect of circulating cortisol on the fetal pituitary and hypothalamus.

Animals↗

PubMed1994

Opposite effects of glucocorticoid on hepatic 11 beta-hydroxysteroid dehydrogenase mRNA and activity in fetal and adult sheep.

The level of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) mRNA in the fetal sheep liver increases dramatically between day 130 and term (term = day 145), but the causal factors remain unknown. The present study was designed to determine the effects of exogenous glucocorticoid on the fetal hepatic 11 beta-HSD gene expression. Dexamethasone (dex; 2 micrograms/min over 15 min every 2 h) or saline was infused into chronically-catheterized fetal sheep at day 130 of gestation for 4 days. At the end of infusion, the lower right lobe of the liver was collected, total cellular RNA extracted and subjected to Northern blot analysis. It was found that the level of the hepatic 11 beta-HSD mRNA in dex-treated fetuses was about four times higher than that in the saline-treated controls. To examine whether changes occur in the response of hepatic 11 beta-HSD gene expression to glucocorticoids in adulthood, we also treated non-pregnant ewes with dex (10 mg/day) for 4 days. By contrast, this treatment regime in adult sheep produced a small but significant decrease in hepatic 11 beta-HSD mRNA levels. We also determined whether age-specific changes in the hepatic level of 11 beta-HSD mRNA following dex treatment were reflected in the level of 11 beta-HSD enzyme activity. Hepatic 11 beta-HSD activity was determined by a standard in vitro conversion assay using cortisol and cortisone as physiological substrates. In both fetal and adult livers, 11-oxoreductase activity (cortisone-->cortisol) was predominant.(ABSTRACT TRUNCATED AT 250 WORDS)

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1993

Tissue distribution of alpha 1-proteinase inhibitor messenger ribonucleic acid and its regulation by glucocorticoids in fetal and neonatal sheep.

alpha 1-Proteinase inhibitor (alpha 1-PI) controls several proteinases that play important roles during inflammation and tissue remodeling, but its function during mammalian development remains obscure. We have therefore studied the ontogeny of alpha 1-PI mRNA in selected fetal and newborn sheep tissues by Northern blotting. Furthermore, because glucocorticoids play important roles in fetal maturation and parturition in sheep, we measured the relative amounts of glucocorticoid receptor (GR) mRNA in the same tissues and compared the effect of dexamethasone (DEX) administration on alpha 1-PI mRNA levels in liver and kidney of fetal and adult sheep. In the ontogeny study, a 1.8-kb alpha 1-PI mRNA was found in fetal adrenal gland and lung at Days 60-70 but was low or undetectable in these tissues at later gestational ages. By contrast, the abundance of hepatic alpha 1-PI mRNA did not vary between Days 60 and 130 of gestation, but decreased significantly (p < 0.05) at term (Days 145-147) and in newborn lambs. In the fetal kidney, it was also present between Days 60 and 130, and its relative abundance increased significantly (p < 0.05) in term and newborn lambs. These changes did not correlate with GR mRNA abundance, which was relatively stable in all tissues except the kidney, where a significant (p < 0.05) decrease was observed in neonates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗

PubMed1993

Foetal endocrine maturation.

In domestic ruminants such as the sheep, birth is effected through sequential maturation of the foetal hypothalamic-pituitary-adrenal (HPA) axis, leading to the increased output of cortisol. Factors regulating foetal pituitary adrenocorticotrophin (ACTH) secretion have been delineated, and these include corticotrophin releasing hormone (CRH), arginine vasopressin, prostaglandin (PG) E2 and endogenous opioids. The pre-partum increase in foetal plasma ACTH is associated with a rise in pro-opiomelanocortin (POMC) mRNA in the foetal pars distalis, and with an altered pattern of POMC post-translational processing. Foetal adrenal activation results from an increase in ACTH receptors and enhanced coupling through the Gs protein to adenylate cyclase, and increased expression of key steroidogenic enzymes including P450c17. Cortisol modulates the mechanism by which ACTH activates foetal adrenal function, through specific glucocorticoid receptors (GR) in the foetal adrenal cortex. Although the numbers of GR change with gestation, the relative abundance of GR mRNA does not, pointing to post-translational regulatory mechanisms. Cortisol also stimulates an increase in the concentration of its own high affinity binding protein (corticosteroid binding globulin; CBG) in the foetal circulation, apparently by increasing CBG gene expression in the foetal liver, and by altering the extent of foetal CBG glycosylation in a manner that would be expected to decrease the metabolic clearance of this glycoprotein. Clear evidence for placental CRH and ACTH production is lacking in sheep, but PGE2, produced in increasing amounts by the placenta during late pregnancy, may augment the drive to HPA maturation. Aspects of the maturational pathway of cortisol biosynthesis have been described in other species, including the horse, and some comparison is made with the more detailed information currently available from species such as the sheep.

Animals↗

PubMed1993

Changes in the abundance of mRNA for type-I 3 beta-hydroxysteroid dehydrogenase/delta 5-->delta 4 isomerase in the human placenta and fetal membranes during pregnancy and labor.

A local decrease in progesterone synthesis in the placenta and fetal membranes has long been proposed as a possible mechanism in the control of human labor. We have examined whether changes occur in the abundance of mRNA for 3 beta-hydroxysteroid dehydrogenase/delta 5-->delta 4 isomerase (3 beta-HSD), the enzyme which catalyzes the conversion of pregnenolone to progesterone in human placenta and fetal membranes, by Northern blot analysis using a cDNA probe to human placental type-I 3 beta-HSD, the predominant isoenzyme in the placenta. The abundance of 3 beta-HSD mRNA (1.7-kb transcript) was about 10-fold greater in term placenta than in chorio-decidua, but undetectable in total RNA from amnion. There was no change in the abundance of 3 beta-HSD mRNA in either placenta or chorio-decidua obtained after elective cesarean section at term, after preterm labor, or after term or postterm vaginal delivery. We conclude that the abundance of 3 beta-HSD mRNA does not change in the placenta or fetal membranes with labor, consistent with the view that changes in 3 beta-HSD gene expression and decreased progesterone production are unlikely to effect intrauterine paracrine/autocrine regulatory mechanisms leading to term or preterm labor in women.

Blotting, Northern↗

PubMed1993

Glucocorticoid-induced increase in plasma corticosteroid-binding globulin levels in fetal sheep is associated with increased biosynthesis and alterations in glycosylation.

In fetal sheep, there is a concomitant prepartum rise in cortisol and corticosteroid-binding globulin (CBG) that maintains a low free plasma cortisol level and allows for a low negative feedback effect of cortisol on the secretion of ACTH from the fetal pituitary. However, the stimulus for the prepartum increase in CBG and the mechanism(s) of this effect are not known. It has been proposed that glucocorticoids increase CBG concentrations, and therefore, we infused fetal sheep with the synthetic glucocorticoid dexamethasone (DEX; 2 micrograms/min over 15 min every 2 h for 96 h, n = 5) or saline (n = 5). The plasma corticosteroid-binding capacity increased from 30.0 +/- 2.4 to 55.6 +/- 7.7 and 92.6 +/- 11.1 ng/ml at 48 and 96 h, respectively, of DEX infusion. To examine possible mechanisms of increasing fetal plasma CBG, we first cloned and sequenced a sheep CBG cDNA and purified the protein. This allowed us to deduce the primary structure of ovine CBG and to demonstrate that hepatic CBG mRNA abundance (single transcript of 1.8 kilobases) rose from 0.9 +/- 0.2 to 3.6 +/- 1.6 arbitrary units after 96 h of DEX treatment. Fetal DEX treatment produced a significant increase (7.1 +/- 1.2% to 13.1 +/- 1.4%) in the Concanavalin-A-binding forms of CBG that predominate in adult sheep plasma. There was negligible transfer of purified [125I]CBG from the ewe to fetal plasma, urine, or amniotic fluid. We also injected adult sheep with DEX (10 mg/day for 4 days) and demonstrated a significant decrease in plasma corticosteroid-binding capacity by 24 h, which remained suppressed for the duration of the study. After 96 h of DEX treatment, there was also a significant decrease in adult hepatic CBG mRNA abundance. We conclude that glucocorticoids increase fetal plasma CBG in part by increased hepatic biosynthesis. It may also be accentuated by a change in the glycosylation of CBG, but cannot be attributed to transplacental transfer. Furthermore, glucocorticoid treatment exerts opposite effects on CBG biosynthesis in fetal and adult sheep.

Amino Acid Sequence↗

PubMed1990

Cortisol inhibits ACTH but not the AVP response to hypoxaemia in fetal lambs at days 123-128 of gestation.

During acute hypoxemia in fetal sheep the elevation in ACTH concentration in the fetal circulation at days 125-129 is greater than that at term, but similar rises in AVP occur at both times. To examine whether the diminished ACTH response is due to elevated endogenous cortisol, and if there is differential control of ACTH and AVP release in hypoxemia, we infused either vehicle or cortisol (5 micrograms/min) into fetal sheep at days 123-128 for 5 h before and then during a 2-h period of acute hypoxemia (mean PaO2 decrease 8.2 mmHg) without acidemia. During cortisol infusion, plasma cortisol rose to 40-50 ng/ml, similar to values in term fetuses. In vehicle-infused fetuses, cortisol rose from 2.1 to 7.0 ng/ml at +1 to +2 h of hypoxemia. ACTH rose significantly during hypoxemia in the vehicle-infused fetuses, and this response was attenuated by cortisol infusion. In contrast, fetal AVP rose significantly during hypoxemia both in the presence and absence of cortisol infusion. Fetal breathing movements, and electroocular activity decreased during hypoxemia, and these responses were not altered by cortisol. We conclude that cortisol exerts differential negative feedback on ACTH but not on AVP release during hypoxemia. The maintained AVP response may facilitate cardiovascular adjustments of the fetus to hypoxemia even when endogenous cortisol is elevated, such as near term.

Adrenocorticotropic Hormone↗