Biomedical subjects

J R Challis

Publications and source records attributed to J R Challis.

At least 19 recordsLinked to original sources

PubMed1992

Ontogeny of the distribution and colocalization of calbindin D28K within neural and endocrine cells of the gastrointestinal tract of fetal and neonatal sheep.

Using immunocytochemical techniques we have demonstrated that Calbindin D28K (CaBP) is present in the gastrointestinal tract of ovine fetuses early in development (by day 45). At day 45, CaBP was limited to neuronal elements in the developing intestine. By day 100, CaBP immunoreactivity was abundant in both epithelial endocrine cells and nerves of the submucous and myenteric ganglia. The location of CaBP containing cells and fibers was similar in duodenal sections taken from day 100 and term (145 days), as well as those taken from 24-48 h postnatal lambs. CaBP is colocalized in endocrine cells containing gastrin, glucagon, somatostatin and neurotensin, but not glucose dependent insulinotrophic peptide (GIP). Furthermore, it is extensively colocalized in nerve fibers and cells containing neurotensin but not somatostatin or vasoactive intestinal peptide. The colocalization of CaBP within various endocrine and nerve cells does not change in fetal sheep over the last one-third of gestation and there is no difference between fetal and neonatal sheep.

Animals↗

PubMed1992

Effects of restricting uteroplacental blood flow on concentrations of corticotrophin-releasing hormone, adrenocorticotrophin, cortisol, and prostaglandin E2 in the sheep fetus during late pregnancy.

We have examined the effects of reduced uterine blood flow and prolonged fetal hypoxemia on the temporal relationship between changes in hormones associated with the activity of the pituitary-adrenal axis (corticotrophin-releasing hormone (CRH), adrenocorticotrophin (ACTH), cortisol, and prostaglandin E2 (PGE2) in the ovine fetus at 120-125 days of pregnancy, and we sought evidence for placental secretion of CRH and ACTH during prolonged hypoxemia. Uterine blood flow was reduced by placing an adjustable Teflon clamp around the maternal common internal iliac artery to decrease fetal arterial oxygen saturation from mean values of 59.1 +/- 3.3 to 25.7 +/- 4.6% (+/- SEM, n = 10). There was a transient peak in immunoreactive (IR-) CRH at 1-2 h after reducing uterine blood flow. IR-ACTH rose to peak values at +2 h, then gradually decreased to control level by +12 h. Fetal plasma cortisol and PGE2 concentrations were elevated significantly by +2 and +4 h, respectively, and at 20-24 h. The identity of IR-CRH in fetal plasma and in ovine placental extracts was confirmed by HPLC, but there was no consistent umbilical vein--femoral arterial concentration difference for either IR-CRH or IR-ACTH during normoxemia or hypoxemia. We conclude that a sequence of endocrine changes involving CRH, ACTH, PGE2, and cortisol occurs in the fetus during a prolonged reduction in uterine blood flow. However, we did not obtain evidence, for placental secretion of either CRH or ACTH in response to this manipulation.

Adrenocorticotropic Hormone↗

PubMed1992

Dexamethasone inhibits basal and stimulated prostaglandin E2 output from human placental cells by inhibition of prostaglandin H synthase.

In view of the temporal relation between elevated concentrations of glucocorticoids and prostaglandins (PG) at the time of parturition, we have examined the effects of dexamethasone on PGE2 output by mixed cell preparations from human placentae at term maintained in short-term (48 or 96 h) culture. Dexamethasone inhibited placental PGE2 output in a dose-dependent fashion. The effect on placental cells was more marked than on short-term cultures of amnion cells and was not influenced by the presence of progesterone. Dexamethasone also inhibited stimulated PGE2 output after addition of arachidonic acid. These results suggest that glucocorticoids inhibit placental PG output by a mechanism involving attenuation of PG synthase activity or expression and do not support a direct causal role for elevated maternal or fetal glucocorticoids at term on increased placental PG biosynthesis.

Arachidonic Acid↗

PubMed1992

Localization of 15-hydroxy prostaglandin dehydrogenase in human fetal membranes, decidua, and placenta during pregnancy.

Localization of NAD(+)-dependent 15-hydroxy prostaglandin dehydrogenase (type I-PGDH) may influence local concentrations of bioactive eicosanoids within intrauterine tissues. In early pregnancy (6-9 weeks), IR-PGDH was localized by immunohistochemistry to syncytiotrophoblast, cytotrophoblast, and intermediate trophoblast of placenta. At 23-30 weeks of gestation and at term IR-PGDH was present in syncytiotrophoblast and intermediate trophoblast, but not in cytotrophoblast in placenta. It was absent from amnion, and distributed within the trophoblast cell layer of extraplacental chorion variably at 23-30 weeks, but consistently at term. We speculate that PGDH is ideally localized to metabolize and to maintain low concentrations of primary prostaglandins in the fetal membranes for much of gestation.

Decidua↗

PubMed1992

Gastrin releasing peptide immunoreactivity is present in ovine amniotic fluid and fetal and maternal circulations. MRC Group in Fetal and Neonatal Health and Development.

Using antisera directed towards the C-terminal region of gastrin releasing peptide (GRP), significant quantities of GRP-like immunoreactivity (GRPLI) were detected in ovine amniotic fluid and in the fetal and maternal circulations. The highest GRPLI levels were found in amniotic fluid (2135 +/- 829 fmol/ml, n = 12; mean +/- SEM), followed by those in ovine fetal (604 +/- 267 fmol/ml, n = 13) and maternal plasma (229 +/- 89 fmol/ml, n = 13). On gel filtration chromatography, the predominant GRPLI form in each fluid eluted in an identical position consistent with the entity being of apparently larger molecular size than porcine GRP1-27. Certain fetal plasma samples contained a second GRPLI peak eluting at the void volume. Hence, during ovine pregnancy a GRPLI entity circulates in fetal and maternal plasma; the entity is of apparently larger molecular size than GRP1-27 but contains a structure immunologically indistinguishable from the bioactive c-terminal region of GRP1-27. Given the recognized bioactivities of GRP, this entity may be an important hormone during ovine fetal life.

Amniotic Fluid↗

PubMed1992

Cloning of an ovine 11 beta-hydroxysteroid dehydrogenase complementary deoxyribonucleic acid: tissue and temporal distribution of its messenger ribonucleic acid during fetal and neonatal development.

Glucocorticoids promote the development of many organ systems vital for extrauterine survival, and fetal cortisol provides the trigger for birth in sheep. The activity of glucocorticoids may be influenced at a cellular level by 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which is responsible for the interconversion of cortisol and cortisone. To examine 11 beta-HSD gene expression during fetal development, two overlapping clones which yield a 1.4 kilobase (kb) complementary DNA encoding sheep 11 beta-HSD from a liver library were isolated by using a rat 11 beta-HSD cDNA as the probe. This cDNA contains a 879 base pair open reading frame for a protein of 292 amino acids that has more than 70% sequence identity to rat and human 11 beta-HSDs. To define the tissue distribution of 11 beta-HSD messenger RNA in sheep, selected tissues were collected from one fetus at day 130 and term (approximately 145 days), and from a nonpregnant ewe. Cellular RNA was extracted and subjected to Northern blot analysis, and a single 1.8 kb transcript was detected in the fetal and adult liver, lung, hypothalamus, anterior pituitary, and placenta. This was undetectable in adrenals and kidneys, but a smaller (1.5 kb) transcript was present in fetal and adult kidney RNA. The relative abundance of 11 beta-HSD mRNA was greatest in fetal and adult livers, and it was much higher in adult liver, lung, and kidney than in the corresponding fetal tissues. To examine whether 11 beta-HSD gene expression is developmentally regulated in the fetal sheep, liver, lung, and kidney tissues were taken from fetuses at day 60-70, day 100-110, day 125-130, at term, and from newborn lambs (24-48 h old). In the lung and kidney, the relative abundance of 11 beta-HSD mRNA did not change from day 60 to term but increased in the lungs of newborn lambs. In contrast, 11 beta-HSD mRNA levels in the liver increased between day 125 and term and rose further in the newborn. Collectively, these results demonstrate that 11 beta-HSD gene expression in sheep is regulated in a tissue-specific and developmentally programmed manner.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1992

Diminished insulinotropic effects of gastrin-releasing peptide in pregnant sheep are reproduced by progesterone treatment of nonpregnant animals.

Gastrin-releasing peptide (GRP) is insulinotropic in several species, but possible alterations in this action during pregnancy have not been explored. Therefore, changes in plasma insulin and glucagon concentrations were examined in response to exogenous GRP in nonpregnant and pregnant sheep that were feed restricted, fed ad libitum, or infused with glucose. Administered GRP provoked insulin and glucagon release in pregnant and nonpregnant fed animals. This effect was reduced with feed restriction and potentiated in the presence of glucose. The responses were less in pregnant than in nonpregnant animals. Interpretation of this result, however, was confounded by lower plasma immunoreactive concentrations of GRP achieved in pregnant than in nonpregnant sheep in response to the same infusion rate (picomoles per kg BW) of exogenous GRP. Therefore, nonpregnant ovariectomized sheep were treated with estradiol (E2) or E2 plus progesterone (P4), given to reproduce circulating steroid levels in pregnancy, in order to examine insulinotropic responses to GRP in the absence or presence of concurrent glucose administration. Similar plasma GRP and glucose concentrations were achieved by exogenous infusions in the different groups of nonpregnant animals treated with steroids and in control animals not receiving steroids. E2 alone did not alter the insulin response to GRP compared to control, but E2 plus P4 treatment attenuated these responses to values similar to those in pregnant animals. We conclude that GRP is insulinotropic in sheep, and this action is modulated by the circulating glucose concentration. The response to GRP is less in pregnant than in nonpregnant animals, and this attenuation is mimicked in nonpregnant animals treated with E2 plus P4. We suggest that in species such as sheep, GRP is a potentiator of glucose-stimulated insulin release. This action is diminished in response to the altered endocrine environment of pregnancy and may contribute to the metabolic changes that occur at this time.

Animals↗

PubMed1992

Insulin-like growth factor-II (IGF-II) messenger ribonucleic acid is expressed in steroidogenic cells of the developing ovine adrenal gland: evidence of an autocrine/paracrine role for IGF-II.

Insulin-like growth factors (IGFs) are potent mitogenic and differentiation-promoting factors that regulate the growth and development of many fetal tissues. Their role in the development of the adrenal gland and activation of its function is not known. The latter is crucial in providing the stimulus for the maturation of various fetal organs and determines the onset of parturition in sheep. To examine the hypothesis that IGFs are important autocrine/paracrine regulators of fetal adrenal development in vivo, we localized IGF-I and IGF-II mRNAs and peptides in the adrenal glands of developing sheep fetuses and correlated the cellular distribution with localization of 3 beta-hydroxysteroid dehydrogenase, tyrosine hydroxylase, and phenylethanolamine-N-methyltransferase enzymes by immunohistochemistry. Adrenal glands from 60- to 75-day-old (n = 4), 100- to 110-day-old (n = 4), 120- to 130-day-old (n = 4), and 145- to 147-day-old (term; n = 4) fetal sheep and 1- to 4-day-old newborn lambs (n = 4) were dissected and either snap-frozen or fixed. Total RNAs were subjected to Northern analysis using ovine IGF-I and IGF-II cDNA probes. Seven IGF-II transcripts of 1.2-6.0 kilobases (kb) were identified in the adrenal glands of fetuses at all gestational ages, and in the newborn. By densitometry, the abundance of IGF-II mRNA was highest in the fetal adrenal gland at 60 days, decreased slightly between 60 and 100 days, remained relatively constant until term, and decreased significantly after birth. At all gestational ages, IGF-II mRNA was detectable in significantly greater abundance than IGF-I mRNA. IGF-I and IGF-II mRNAs were localized by in situ hybridization using 35S-labeled anti-sense cRNA probes, and the peptides by immunohistochemistry using specific antisera. Low levels of IGF-I mRNA were detected in the zona fasciculata, but not in the zona glomerulosa. There was strong hybridization of the IGF-II cRNA to the zona glomerulosa and fasciculata and to the capsule. The hybridization signal was greater in the zona fasciculata than in the zona glomerulosa. IGF-II mRNA was also detected in groups of cells within the medulla. Localization of IGF-II mRNA by in situ hybridization correlated well with the distribution of IGF-II immunoreactivity and with 3 beta-hydroxysteroid dehydrogenase-positive cells in the cortex and in groups of cells within the medulla.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Cortex↗

PubMed1992

Immunohistochemical localization of 3 beta-hydroxy-5-ene-steroid dehydrogenase/delta 5----delta 4 isomerase in human placenta and fetal membranes throughout gestation.

The regulation of steroid production by the placenta and fetal membranes is important for both the maintenance of pregnancy and the timing of parturition. 3 beta-Hydroxy-5-ene-steroid dehydrogenase/delta 5----delta 4-isomerase (3 beta HSD) catalyzes an obligatory step in the biosynthesis of steroid hormones. We have determined the localization of 3 beta HSD in the human placenta, fetal membranes, and umbilical cord throughout gestation by immunohistochemical analysis, using a polyclonal antibody raised in rabbits against a purified preparation of human placental 3 beta HSD. In placenta, immunoreactive (IR-) 3 beta HSD was localized in the syncytiotrophoblast and intermediate trophoblast cells at both villous and extravillous sites, but not in cytotrophoblast cells from 6 weeks gestation to term. At 6-7 weeks gestation, IR-3 beta HSD was distributed in the cytoplasm of syncytiotrophoblast in about half of placental villi. By 12-14 weeks, the syncytiotrophoblast of all placental villi stained positively for 3 beta HSD. In the fetal membranes, strong IR-3 beta HSD staining was found in the trophoblast and reticular layers of chorion and in invasive trophoblast cells in decidua, and weakly in decidual stromal cells and amniotic epithelium. No IR-3 beta HSD was found in amnion on the placental plate, but in the umbilical cord, IR-3 beta HSD was present in the amniotic epithelium and also in fibroblast cells in Warton's jelly. These observations demonstrate that the localization of 3 beta HSD immunoreactivity and, therefore, the presumed sites of delta 5- to delta 4-steroid interconversion throughout gestation are principally the syncytiotrophoblast and intermediate trophoblast cells in placenta and the trophoblast cells in chorion and decidua in fetal membranes.

Extraembryonic Membranes↗

PubMed1992

Immunohistochemical localization of 3 beta-hydroxysteroid/delta 5-delta 4-isomerase, tyrosine hydroxylase and phenylethanolamine N-methyl transferase in adrenal glands of sheep fetuses throughout gestation and in neonates.

Immunoreactive 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase (3 beta-HSD) was localized in adrenal glands of sheep fetuses in cortical-type cells, but not in medullary-type cells, from day 43 of gestation to term and in 2-4-day-old neonates. From day 54 of gestation, the formation of distinct zones within the adrenal cortex was apparent and immunoreactive 3 beta-HSD was found in cortical cells in the zona fasciculata and in groups and cords of cortical cells within the developing medulla, with weak positive staining in the zona glomerulosa. At this stage, most medullary cells were positive for immunoreactive tyrosine hydroxylase, and some of these cells with a juxtacortical distribution also stained positively for immunoreactive phenylethanolamine N-methyl transferase (PNMT). Between days 65 and 130, the adrenal medulla increased in size with little change in the width of the cortex. Organization and zonation of immunoreactive 3 beta-HSD staining cells were evident in the zona fasciculata and in groups of cells in the medulla. Between day 130 and term, uniform immunoreactive 3 beta-HSD staining was found throughout the zona fasciculata, and there was also staining in single cells and small clusters of cells throughout the medulla. At this stage, immunoreactive tyrosine hydroxylase was distributed in most cells throughout the medulla, but in two distinct patterns: cells staining intensely for immunoreactive tyrosine hydroxylase in the central region of the medulla, and cells exhibiting weaker staining for immunoreactive tyrosine hydroxylase localized in a juxta-cortical position. These juxta-cortical cells were also positive for immunoreactive PNMT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗

PubMed1992

Characterization of an ovine glucocorticoid receptor cDNA and developmental changes in its mRNA levels in the fetal sheep hypothalamus, pituitary gland and adrenal.

Fetal sheep tissues possess glucocorticoid receptors (GR), and these change in number during the last two-thirds of gestation. There is, however, no information about developmental changes in tissue GR mRNA levels which might account for alterations in fetal GR content. We have therefore cloned and sequenced a 942 bp GR cDNA from a sheep liver cDNA library, and used it to study the relative abundance of GR mRNA in fetal and neonatal sheep tissues. Analysis of the cDNA revealed a partial sequence of the ovine GR which displayed over 80% identity with residues 143-453 in human GR and 163-472 in rat GR. Furthermore, the first zinc finger motif in these receptors was perfectly conserved among species. The relative abundance of GR mRNA was studied in hypothalami, anterior pituitary glands and adrenals in fetuses at days 60-70, 100-110, 125-130 and at term (approximately 145 days), and in newborn lambs. Total RNA extracts (20 micrograms) were analysed by Northern blot analysis. A single 5.6 kb transcript was detected in all three fetal tissues, and its relative abundance did not change significantly throughout gestation. However, in newborn lambs, levels of GR mRNA increased significantly in the hypothalamus and pituitary gland but decreased to undetectable levels in the adrenal. These tissue-specific changes in the relative abundance of GR mRNA did not correlate with alterations in GR content in fetal tissues, which suggests that the latter may reflect alterations in GR mRNA translation, subsequent modifications and/or GR turnover. In addition, the pattern of developmental changes in GR mRNA content of the adrenal differs from that of the hypothalamus and pituitary gland in neonatal lambs, and indicates that tissue-specific factors may influence GR gene expression in neonatal sheep.

Adrenal Glands↗

PubMed1992

Adrenocorticotrophin responses to hypoxaemia in fetal sheep are sustained in the presence of naloxone.

We have examined the effects of fetal hypoxaemia, produced by reducing the percent oxygen in maternal inspired air, on fetal plasma concentrations of corticotrophin releasing hormone (CRH), adrenocorticotrophin (ACTH) and cortisol and determined the effects of an opioid receptor antagonist, naloxone on these responses. Hypoxaemia (fetal PO2, 15-18 mmHg) for 60 min provoked a significant (P < 0.05) increase in fetal plasma ACTH and cortisol concentrations at days 125-130 of pregnancy, but did not affect circulating CRH. There was no effect of naloxone administered either intravenously (1.25 mg bolus followed by a 2.5 mg/h continuous infusion for one hour; fetal body weight approximately 2.5 Kg) or via the lateral cerebral ventricle (50 micrograms bolus followed by a 100 micrograms/h infusion for one hour) on this pattern of ACTH and cortisol change nor on the lack of CRH response to hypoxaemia. We conclude that the increase in fetal ACTH and cortisol in response to acute hypoxaemia is not accompanied by an increase in systemic CRH concentrations, nor is the response dependent on short-term opioid regulation.

Adrenocorticotropic Hormone↗

PubMed1991

Immunohistochemical localization of prostaglandin H synthase in the sheep placenta from early pregnancy to term.

Prostaglandin H synthase (PGHS) activity within intrauterine tissues is considered to catalyze a critical step in prostaglandin (PG) biosynthesis at parturition. In sheep, the placenta is a major site of PG production throughout pregnancy, but little information is available concerning the cells that are responsible. Therefore we determined the distribution of immunoreactive (IR-) PGHS in ovine placental tissue obtained at different times of pregnancy using immunohistochemical techniques. In placentomes from early pregnancy (Days 30-54), IR-PGHS was present in maternal epithelial syncytium, but was not detectable in trophoblast cells. Between Day 54 and Day 100, the number of cells that stained positive for PGHS declined in the maternal epithelial layer in the body of the placenta, but IR-PGHS was present in maternal epithelial cells overlying the vascular cones of the placental hemophagous zone. It was also present in the chorionic fibroblasts, but remained undetectable from all classes of trophoblast cells. IR-PGHS was first detectable in the trophoblastic epithelium by Day 114. Between Day 119 and term the trophoblast mononuclear epithelial cells were intensely immunopositive for PGHS, although immunonegative binucleate cells were present. The maternal epithelium was immunonegative except during the last 7-10 days of pregnancy when PGHS immunostaining appeared in both basal and apical regions of the placenta. Thus, the cellular localization of IR-PGHS changes during ovine pregnancy, from predominantly maternal during the first half of gestation to undetectable and then to predominantly trophoblastic between Day 114 and term, suggesting a gestation-dependent change in sites of PG production during ovine pregnancy. Appearance of IR-PGHS in the trophoblast precedes activation of the fetal hypothalamic-pituitary-adrenal axis, generally considered to provide the trigger to the onset of parturition in sheep, and would therefore appear to be regulated through alternative pathways or mechanisms.

Animals↗

PubMed1991

DNA synthesis is reduced in selected fetal tissues during prolonged hypoxemia.

The effects of 24 h of reduced maternal uterine blood flow (RUBF) on relative DNA synthesis rates in different tissues and on blood glucose and lactate concentrations were studied in fetal sheep. In six sheep, RUBF was induced for 24 h, whereas in another six sheep (controls), uterine blood flow was not reduced. To estimate DNA synthesis rate, [3H]thymidine (1 mCi/kg) was injected intravenously into each fetus 8 h before the end of the 24-h experimental period. Fetal arterial oxygen saturation decreased from 59.1 +/- 3.3 to 25.7 +/- 5.6% after 1 h of RUBF and remained significantly reduced for the duration of the experiment. Fetal blood lactate concentrations were significantly increased by RUBF from 14.3 +/- 6.5 to 57.8 +/- 12.4 mg/dl at 1 h and remained elevated, whereas fetal blood glucose concentrations were not affected. A 24-h period of RUBF did not significantly alter fetal body weights, tissue weights, tissue-to-body weight ratios, or tissue DNA content. Over the last 8 h of the 24-h experimental period, RUBF was found to significantly reduce the relative rate of DNA synthesis (as assessed by [3H]thymidine incorporation into DNA) in the lung (104.7 +/- 26.6 vs. 17.1 +/- 3.1 dpm/micrograms DNA), quadriceps muscle (92.8 +/- 20.7 vs. 14.4 +/- 5.3 dpm/micrograms DNA), and thymus gland (87.5 +/- 7.1 vs. 32.9 +/- 12.2 dpm/micrograms DNA). Relative DNA synthesis rates in the fetal liver, kidney, small intestine, cerebral cortex, cerebellum, placenta, thyroid gland, and adrenal gland were not significantly affected by RUBF. In this study, we have shown that DNA synthesis was greatly reduced in selected fetal tissues (lung, quadriceps muscle, and thymus gland) by a 24-h period of RUBF, although it is not known why a reduction was only observed in these tissues.

Adrenal Glands↗

PubMed1991

Effect of adrenocorticotropin administration on the biosynthesis of corticosteroid-binding globulin in fetal sheep.

Parturition in sheep is initiated by the fetus through activation of the fetal hypothalamic-pituitary-adrenal axis and is associated with increased concentrations of ACTH, cortisol, and corticosteroid-binding globulin (CBG) in the fetal circulation during the final 10-15 days of pregnancy. Premature parturition and a precocious elevation in fetal plasma CBG are produced by intrafetal ACTH administration, but the possible sources of CBG in the ovine fetus are not known. To determine these sites, CBG mRNA was measured in tissues from fetal sheep in late pregnancy and after intrafetal ACTH treatment, using a sheep CBG cDNA. Fetal ACTH treatment caused a significant increase in the fetal plasma corticosteroid-binding capacity (CBC), although there was no significant difference in CBC between umbilical arterial and umbilical venous plasma. After ACTH treatment, CBC was elevated in fetal liver and kidney. Cortisol binding in these tissues had characteristics similar to those of cortisol binding in fetal sheep plasma. By Northern blot analysis a single mRNA (1.7 kilobases) for CBG was detected in fetal liver, kidney, lung, and adrenal, but not in placenta. The abundance of CBG mRNA in the fetal liver was greater than that in other tissues, but was unchanged by ACTH treatment. The level of CBG mRNA in the fetal kidney, but not in other tissues, increased 3-fold after ACTH. We conclude that the elevation in plasma CBC after intrafetal ACTH, and presumably also at term pregnancy, does not reflect production of CBC by the placenta or transfer from the mother. Rather, it results from production primarily in the fetal liver and kidney, although only in the latter tissue is CBG mRNA accumulation increased by intrafetal ACTH treatment.

Adrenal Glands↗

PubMed1991

The localization and distribution of corticotropin-releasing hormone in the human placenta and fetal membranes throughout gestation.

Using immunohistochemical techniques, we have determined the localization and distribution of CRH immunoreactivity (CRH-IR) in the human placenta, fetal membranes, decidua, and umbilical cord. Tissues were obtained at 6-8 weeks of pregnancy, at term, in association with premature birth, and from patients with pregnancy-induced hypertension or diabetes mellitus. A polyclonal antibody to the epithelial cell marker cytokeratin was used to identify trophoblast cells. CRH-IR was not detected in placenta or decidua at 6-8 weeks gestation. In tissues obtained after idiopathic premature delivery after 21 weeks gestation, positive CRH staining was found in placenta in syncytiotrophoblast and intermediate trophoblast, but not cytotrophoblast. CRH-IR was present in intermediate trophoblast cells that had invaded maternal blood vessels in decidua basalis. In the fetal membranes, CRH-IR was localized in the epithelium and subepithelial cells of amnion, in the trophoblast layer, in some cells of the reticular and cellular layers of chorion, and in some stromal cells and invasive trophoblast cells of decidua. CRH-IR was found in the amniotic epithelium of the umbilical cord and in the musculature of the umbilical vessels. This pattern of distribution of CRH-IR was found in tissues from 21 weeks gestation to term and postterm, and was similar in tissues examined from patients with pregnancy-induced hypertension and diabetes mellitus. These results show clearly that in placenta and membranes, CRH is localized primarily to syncytiotrophoblast and intermediate trophoblast, but not to cytotrophoblast cells. We suggest that the localization of CRH-IR is consistent with CRH affecting paracrine/autocrine interactions within the placenta, fetal membranes, and decidua that may be involved in the maturation of the fetal hypothalamic-pituitary-adrenal axis and in the stimulus and maintainance of labor.

Amnion↗

PubMed1991

Immunoreactive adrenocorticotrophin is present in the ovary and in particular the oocyte of several mammalian species.

Proopiomelanocorticotrophin (POMC)-derived peptides have been identified in both male and female reproductive systems. However, there have been few reports of ACTH, the major biologically active POMC product, in the mammalian ovary. We sought evidence for the presence and localization of immunoreactive (ir)-ACTH in ovaries from sheep, humans, cows, pigs, rats and cats using immunohistochemical techniques. Tissue sections were stained with diaminobenzidine following incubation with a primary antibody raised against ACTH1-24. There was positive staining for ACTH in cells scattered throughout the interstitium of ovaries from all species examined. Immunoreactive ACTH was observed in the oocytes of ovaries from humans, cows, pigs, pregnant and non-pregnant sheep, but not from cats or rats. Positive staining of oocytes was associated with all tertiary and secondary follicles, and some primary follicles. There was no apparent difference in the pattern of staining between pregnant and non-pregnant sheep. Staining for ir-ACTH was absent in ovaries from fetal sheep. We conclude that ir-ACTH is present in ovarian tissue, and in particular the oocyte, from several species of mammal. The presence of ir-ACTH within the oocyte is dependent on species and stage of follicular maturation.

Adrenocorticotropic Hormone↗

PubMed1991

Characteristics and developmental changes of corticotrophin-releasing hormone-binding sites in the fetal sheep anterior pituitary gland.

The responses of the fetal sheep pituitary to corticotrophin-releasing hormone (CRH) change during gestation with maximum output of ACTH around days 120-130, and decreased ACTH output near term. However, there is no information available concerning the extent to which these responses may be modulated by alterations in the number of CRH receptors. Therefore we measured specific CRH-binding sites, and changes in binding characteristics in membrane preparations from fetal sheep anterior pituitaries collected at days 65-70, 85-88, 100-110, 125-130 and at term (approximately 145 days). Binding assays were carried out using 125I-labelled Tyr-ovine CRH (125I-Tyr-oCRH), incubated with crude membrane fractions for 90 min at 22 degrees C. Binding was time- and temperature-dependent, linear with protein concentration, saturable and specific for oCRH. Scatchard analysis of binding data for individual tissues revealed a single class of CRH-binding sites with high affinity (Kd congruent to 1 nmol/l) that did not change significantly with gestational age. However, the number of CRH-binding sites increased progressively from days 65-70 to a maximum at days 125-130, then decreased at term. These results demonstrate the presence of specific CRH-binding sites in the fetal sheep anterior pituitary. Furthermore, the change in CRH receptor number with advancing pregnancy follows a similar time-course to the changes reported previously in responsiveness of the fetal sheep anterior pituitary to exogenous CRH stimulation in vivo. These results suggest that alterations in CRH receptor number may contribute to changes in responsiveness of the fetal sheep anterior pituitary to CRH during gestation.

Adrenocorticotropic Hormone↗