Biomedical subjects

Roger Smith

Publications and source records attributed to Roger Smith.

At least 55 records · Page 3Linked to original sources

PubMed2003

Maternal asthma is associated with reduced female fetal growth.

Asthma during pregnancy is associated with a low birth weight, although the mechanisms contributing to this outcome remain unknown. The relationship between maternal asthma and its treatment, placental function, fetal sex, and low birth weight was examined to establish the effect of asthma on fetal growth. Glucocorticoid intake by women with asthma was assessed throughout pregnancy. The placenta was collected after delivery, and 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) activity was measured. Fetal cortisol and estriol were measured in the umbilical vein plasma at delivery. Those with asthma were compared with a nonasthmatic control group. In women with asthma who did not use inhaled steroids and were pregnant with a female fetus, we observed significantly reduced birth weights, whereas male birth weights were unaffected. The presence of a female fetus was associated with significantly increased maternal circulating monocytes, significantly reduced placental 11beta-HSD2 activity and fetal estriol, and a trend toward elevated fetal plasma cortisol. This study provides evidence that in pregnancies complicated by asthma there is a fetal sex-specific effect on the maternal immune system with adverse effects on placental function and female fetal growth.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗

PubMed2003

Early changes in metabolism of leukemic cell lines upon induction of apoptosis by cytotoxic drugs.

We evaluated real-time changes in extracellular acidification rates of human U937 and K562 leukemic cells treated with camptothecin or taxol. U937 cells treated with camptothecin or taxol for 30-60 min showed a continuous, irreversible decrease in extracellular acidification rate that was sensitive to amiloride. In contrast, U937 cells exposed to sodium azide showed an immediate, steep decrease in extracellular acidification rate that was reversible upon azide withdrawal. K562 cells required a >20-fold higher dose of camptothecin to promote similar changes in the extracellular acidification rate, with a corresponding resistance in their susceptibility to camptothecin- or taxol-induced apoptosis. The data show that irreversible commitment to apoptosis is associated with rapid metabolic changes that are reflected by decreased extracellular acidification rate and regulated by the Na(+)/H(+) antiporter. Moreover, detection of extracellular acidification rate changes was not restricted to a particular cell type or apoptosis pathway, making this a potentially useful tool to screen compounds for pro-apoptotic activity.

Amiloride↗

PubMed2003

Peroxisome proliferator-activated receptor gamma agonists induce proteasome-dependent degradation of cyclin D1 and estrogen receptor alpha in MCF-7 breast cancer cells.

Treatment of MCF-7 cells with the peroxisome proliferator-activated receptor (PPAR) gamma agonists ciglitazone or 15-deoxy-Delta 12,14-prostaglandin J2 resulted in a concentration- and time-dependent decrease of cyclin D1 and estrogen receptor (ER) alpha proteins, and this was accompanied by decreased cell proliferation and G(1)-G(0)-->S-phase progression. Down-regulation of cyclin D1 and ER alpha by PPARgamma agonists was inhibited in cells cotreated with the proteasome inhibitors MG132 and PSII, but not in cells cotreated with the protease inhibitors calpain II and calpeptin. Moreover, after treatment of MCF-7 cells with 15-deoxy-Delta 12,14-prostaglandin J2 and immunoprecipitation with cyclin D1 or ER alpha antibodies, there was enhanced formation of ubiquitinated cyclin D1 and ER alpha bands. Thus, PPARgamma-induced inhibition of breast cancer cell growth is due, in part, to proteasome-dependent degradation of cyclin D1 (and ER alpha), and this pathway may be important for other cancer cell lines.

Breast Neoplasms↗

PubMed2003

Assessment of temporal biochemical and gene transcription changes in rat liver cytochrome P450: utility of real-time quantitative RT-PCR.

PURPOSE: A conventional approach to assess cytochrome P450 (CYP) induction in preclinical animal models involves daily dosing for a least a week followed by Western blot and/or enzyme activity analysis. To evaluate the potential benefit of a third more specific and sensitive assay, real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), with the objective of reducing the duration of the conventional 1-week study, we simultaneously assessed gene expression by qRT-PCR along with Western blots and enzyme activity assays as a time course in an in vivo model. METHODS: Rats were dosed daily for 8 days with model inducers of CYP1A, CYP2B, CYP3A, or CYP4A. Liver P450 levels were measured after 0.5, 1, 2, 4, and 8 days of dosing by qRT-PCR, Western blot, and enzyme activity. RESULTS: CYP1A, CYP3A, and CYP4A genes were maximally induced very rapidly (0.5-1 day), whereas the CYP2B gene was maximally induced after a lag time of 4 days. In all cases, fold changes in induction detected by qRT-PCR were greater than fold changes in protein levels and enzyme activities. CONCLUSIONS: Maximal persistent and larger fold changes observed by qRT-PCR either preceded or occurred simultaneously with maximal sustained fold changes in protein levels as measured by Western blots and enzyme activity assays. Our data show that qRT-PCR provides increased sensitivity and specificity over conventional assays and may be key information for reliable assessment of drug-related changes in CYP induction during the transition from discovery to toxicology studies.

Animals↗

PubMed2003

Aryl hydrocarbon receptor gene silencing with small inhibitory RNA differentially modulates Ah-responsiveness in MCF-7 and HepG2 cancer cells.

Sequence-specific small interfering RNA (siRNA) duplexes can be used for gene silencing in mammalian cells and as mechanistic probes for determining gene function. Transfection of siRNAs for the aryl hydrocarbon receptor (AhR) and AhR nuclear translocator (ARNT) mRNAs in MCF-7 breast cancer cells resulted in a 60 to 80% decrease in levels of AhR and ARNT proteins in whole-cell extracts and decreased binding of nuclear extracts to 32P-labeled dioxin-responsive element. siRNA for the AhR also decreased 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1 protein, CYP1A1-dependent activity, and luciferase activity in cells transfected with an Ah-responsive construct. 17beta-estradiol (E2) induces proliferation of MCF-7 cells through enhanced G0/G1 --> S phase progression, and this response is inhibited in cells cotreated with E2 plus TCDD. The effects of TCDD on E2-induced cell-cycle progress were partially blocked in MCF-7 cells transfected with siRNA for AhR. The results also indicated that siRNA-dependent decreases in AhR protein in MCF-7 cells were accompanied by increased G0/G1 --> S phase progression, suggesting a growth-inhibitory role for the "endogenous" AhR. Surprisingly, TCDD alone induced G0/G1 --> S phase progression and exhibited estrogenic activity in MCF-7 cells transfected with siRNA for the AhR. In contrast, degradation of the AhR in HepG2 liver cancer cells resulted in decreased G0/G1 --> S phase progression, and this was accompanied by decreased expression of cyclin D1, cyclin E, cyclin-dependent kinase 2 (cdk2), and cdk4. In the absence of ligand, the AhR exhibits growth-inhibitory (MCF-7) and growth-promoting (HepG2) activity that is cell context-dependent.

Aryl Hydrocarbon Receptor Nuclear Translocator↗

PubMed2003

Corticotropin-releasing hormone causes vasodilation in human skin via mast cell-dependent pathways.

CRH plays a central role as a mediator of the hypothalamic-pituitary-adrenal axis and stress response and is a potent vasodilator. Previously, we have shown that CRH causes a gender-specific vasodilation in human skin, although the mechanism by which CRH operates is unclear. CRH causes mast cell degranulation in rat skin. As such, histamine and other mast cell-derived factors may be indirectly responsible for the vasodilatory effects of CRH, although CRH is also known to act directly on the vasculature. CRH-induced vasodilation in human skin was examined using laser Doppler flowmetry and iontophoresis in adult females. CRH (1 nM) was administered iontophoretically to the forearm, and blood flow was measured simultaneously in the same area by laser Doppler. CRH-induced dilation of the skin microvasculature was significantly reduced in the presence of the mast cell degranulation inhibitor, sodium cromoglycate, the histamine H(1)-antagonist, promethazine, or the H(2)-antagonist, ranitidine. CRH-induced dilation was also significantly reduced in the presence of the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester, or the cyclooxygenase inhibitor, piroxicam. These findings provide novel evidence that CRH-induced vasodilation in human skin occurs via mast cell degranulation and is principally mediated by histamine and, to a lesser extent, by prostacyclin and nitric oxide.

Cell Degranulation↗

PubMed2003

A multi-exponential model of postmenopausal decline in vertebral bone mineral density: a new approach to the BMD reference range.

Although the postmenopausal decline in female bone mineral density (BMD) at the lumbar spine is central to the World Health Organization (WHO) diagnosis of osteoporosis, it has eluded an exact mathematical description. We present a simple mathematical model based on the assumption that bone loss can be described as an exponential decay process that begins at menopause. Women whose menopause begins in the same year of age are assigned a unique exponential function, and results from all women are combined to predict the average cross-sectional BMD on a year-by-year basis. This model has been successfully validated using data from a cross-sectional study of 8,789 female volunteers. No additional "aging" term is required. The normal time-constant was estimated to be 5.8 yr, but natural variation can have a substantial asymmetric effect on the curve. Similarly, variation in the distribution of the age at menopause also has a profound influence and can introduce artifacts when different populations of women are being compared. Using published data from Finland, it was confirmed that a simulation approach can predict the BMD decline observed in typical cross-sectional studies, suggesting the possibility of a cheaper and more convenient way to establish local dual-energy X-ray absorptiometry (DXA) reference curves.

Adult↗

PubMed2002

Hormone trajectories leading to human birth.

The mechanisms regulating human parturition and labor remain unknown. This ignorance is expensive as preterm birth is responsible for 70% of neonatal mortality and 50% of cerebral palsy. Methods for the prediction of preterm birth and treatments for women in preterm labor have poor efficacy reflecting our limited knowledge of the mechanisms involved. Recent research has supported the view that parturition is a cascade of events that commences early in pregnancy and involves the mother, fetus, placenta, membranes, cervix and myometrium. Although a number of the key hormones and proteins involved have been identified, the relationships between these factors in time and tissues remain unclear. Placental production of Corticotropin-releasing hormone (CRH) is proposed as an early event regulating the cascade of events. Central to the onset of parturition will be a mechanism for progesterone withdrawal and estrogen activation in human. Two forms of progesterone receptor with opposing actions exist in the human myometrium. Progesterone receptor A (PR-A) is a dominant negative repressor of progesterone receptor B (PR-B). Preliminary studies strongly support the hypothesis that the onset of human parturition is initiated by rising concentrations of PR-A in the myometrium.

Female↗

PubMed2002

Novel glucocorticoid and cAMP interactions on the CRH gene promoter.

Glucocorticoids inhibit corticotrophin releasing hormone (CRH) production in the hypothalamus but stimulate production from the placenta. We have sought to identify the key elements regulating the CRH gene. Mouse pituitary tumour-derived cells (AtT20 cells) were used in deletion and mutational analyses of the CRH promoter. Two cAMP responsive elements were identified: (I) a consensus cAMP response element (CRE) and (II) a previously unrecognised caudal-type homeobox response element (CDXRE). Glucocorticoids inhibit only the component of cAMP-stimulation occurring via the CRE through an action involving a negative glucocorticoid response element (nGRE). We also identified two regions that, in the absence of the nGRE, can be stimulated by glucocorticoids: (I) the CRE and (II) a region between -213 and -99 bps. Electrophoretic mobility shift assays (EMSAs) identified binding of the transcription factors CREB and Fos at the CRE in AtT20 cells while CREB and cJun were detected in placental cells. Tissue specific expression of transcription factors may mediate regulation of the CRH gene.

Animals↗

PubMed2002

Small inhibitory RNA duplexes for Sp1 mRNA block basal and estrogen-induced gene expression and cell cycle progression in MCF-7 breast cancer cells.

Small interfering RNA duplexes containing 21-22 nucleotides that mediate sequence-specific mRNA degradation and inhibitory RNA (iRNA) for Sp1 mRNA were used in this study to investigate the role of Sp1 on basal and hormone-induced growth and transactivation in MCF-7 and ZR-75 human breast cancer cells. Transfection of Sp1 iRNA in MCF-7 or ZR-75 cells for 36-44 h decreased Sp1 protein (50-70%) in nuclear extracts, and immunohistochemical analysis showed that the Sp1 protein in transfected MCF-7 cells was barely detectable. In cell cycle progression studies in MCF-7 cells, decreased Sp1 protein was accompanied by a decrease in cells in the S phase and an increase in cells in G(0)/G(1), and estrogen-induced G(0)/G(1) --> S phase progression was inhibited in cells treated with iRNA for Sp1. Sp1 iRNA also specifically blocked basal and estrogen-induced transactivation in cells transfected with a GC-rich construct linked to a luciferase reporter gene (pSp1(3)), and this was accompanied by decreased Sp1 binding to this GC-rich promoter as determined in gel mobility shift and chromatin immunoprecipitation assays. These results clearly demonstrate the key role of the Sp1 protein in basal and estrogen-induced growth and gene expression in breast cancer cells.

Breast Neoplasms↗

PubMed2002

Chromatographic behaviour of selected steroids and their inclusion complexes with beta-cyclodextrin on octadecylsilica stationary phases with different carbon loads.

Retention and separation studies of selected estrogens, progestogens and their inclusion complexes with beta-cyclodextrin were conducted using two C18 HPLC columns with different carbon loads. The difference in carbon load between investigated octadecylsilica packing materials was about 50%. The mobile phases were composed of a 30% v/v acetonitrile-water mixture without and with addition of beta-cyclodextrin at a concentration of 12 mM. The experimental data revealed that retention of the steroids was significantly reduced on the column with the lower carbon load. Moreover, it was found that this column offers better separation power and shorter analysis time at the temperatures studied. However, the calculated values of the retention factor ratios (k0(mMCD))/k(12mMCD)) of the steroids were similar for both columns investigated. This observation suggests that the stationary phase structure appears to have little effect on the formation of host-guest complexes if the complexation process is localised to the chromatographic mobile phase. From a practical point of view, when the mobile phase is modified with beta-cyclodextrin, the separation of the steroids is strongly influenced by temperature. The best chromatographic conditions were determined for the separation of multicomponent samples on the column with lower carbon load. A possible retention mechanism for components of interest in the presence of macrocyclic additives is discussed.

Carbon↗

PubMed2002

Maternal plasma corticotropin-releasing hormone trajectories vary depending on the cause of preterm delivery.

OBJECTIVE: Although second trimester maternal plasma corticotropin-releasing hormone concentrations are elevated in women who are destined to deliver preterm, the sensitivity and positive predictive value of an individual test of corticotropin-releasing hormone concentration is low. This poor screening performance may be due in part to the observation that the causes of preterm delivery are heterogenous, with potentially different effects on corticotropin-releasing hormone production. We have reanalyzed data from a previous cohort of women with multiple samplings to determine whether the trajectory of increase of placental corticotropin-releasing hormone provided more information than did a single sample. STUDY DESIGN: In this cohort, where 2 to 4 samples that had been assayed for corticotropin-releasing hormone were available on 305 women, the general form of the exponential equation y = ae(bt) was fitted to the corticotropin-releasing hormone data of each individual by the Gauss-Newton nonlinear least squares method, which generated the parameters, y-intercept and rate of rise, in corticotropin-releasing hormone concentration for each woman. Nonparametric statistical techniques, including bootstrapping, were applied to compare the results for the group of women who delivered at term with the group of women who delivered spontaneously preterm and the group of women who were delivered preterm by induction or cesarean delivery because of obstetric indication. RESULTS: The 3 clinically defined groups have significantly different parameters, y-intercept and rate of rise, which describe the corticotropin-releasing hormone trajectory. The group that delivered preterm because of obstetric indications had a similar mean y-intercept but significantly greater mean rate of rise in corticotropin-releasing hormone concentration than the term group (0.3491 vs 0.1788; 95% CI, 0.2331-0.4615 vs 0.1394-0.2330). The group that delivered spontaneously preterm had a significantly greater mean y-intercept than the group that delivered preterm because of obstetric indication (17.08 vs 1.83; 95% CI, 5.89-28.43 vs 0.03-5.19) but a similar mean rate of rise to the group that delivered at term. CONCLUSION: These data suggest that spontaneous preterm delivery is associated with an abnormal setting of the production of corticotropin-releasing hormone that is present from very early in pregnancy, although women who experience an induced preterm delivery are characterized by rapidly rising placental corticotropin-releasing hormone concentrations. These data further suggest that clinical abnormalities that are associated with preterm delivery by induction or cesarean delivery are associated with abnormalities that lead to a rapidly increasing corticotropin-releasing hormone concentrations. Trajectories for corticotropin-releasing hormone provide information beyond that obtained from a single sample.

Cesarean Section↗

PubMed2002

Prediction of preterm delivery using plasma corticotrophin-releasing hormone and other biochemical variables.

Preterm delivery is responsible for the vast majority of neonatal mortality in developed countries and is also associated with substantial long-term morbidity. The incidence of preterm birth remains between 6-10% despite many advances in our understanding of the physiology of human parturition. Biochemical markers have been used in an attempt to identify more accurately those women, amongst high and low-risk groups who will deliver preterm, from their counterparts who will go on to deliver at term. Only by accurately identifying those women early, who will eventually deliver preterm, will specific interventions be able to be used in order to try and treat the cause or delay delivery until a safer time for the fetus. The clinical utility of these markers when used alone in an unselected population remains limited. As our understanding of the pathophysiology of preterm delivery improves, the challenge lies for researchers to combine these markers in the most effective way to unravel the complex biological system of parturition and improve the predictive capability of a biochemical test for prematurity.

Adrenocorticotropic Hormone↗

PubMed2002

Quantitation of reticulated platelets in healthy dogs and in nonthrombocytopenic dogs with clinical disease.

BACKGROUND: Thrombocytopenia is a common disorder in dogs and development of an objective diagnostic assay to measure platelets newly released from bone marrow into the blood would provide a noninvasive way to predict megakaryocytopoiesis. Reticulated platelets are newly released platelets with increased concentrations of RNA that can be detected by flow cytometric analysis of blood stained with thiazole orange (TO). OBJECTIVE: The goals of this study were to establish a reproducible method to quantitate reticulated platelets in dogs, to establish a reference interval for reticulated platelet percentages in healthy dogs, and to determine whether the percentage of reticulated platelets was nonspecifically increased in nonthrombocytopenic dogs with clinical disease. METHODS: Blood samples were obtained from healthy dogs and from nonthrombocytopenic dogs presented for a variety of disorders. An aliquot of whole blood was stained with TO and a phycoerythrin-labeled monoclonal antibody to platelet CD61, then analyzed by flow cytometry. RESULTS: The coefficients of variation were 7.8% to 15.6% (intra-assay precision) and 6.1% to 19.5% (interassay precision). Overnight storage for 18 to 26 hours, under variable conditions, resulted in an increase in the percentage of platelets staining with TO. The reference interval for reticulated platelets in the healthy control group was 0-4.3% (0-12,095/microL). No significant differences were found in the mean percentage of reticulated platelets or absolute concentration of reticulated platelets between control and affected dogs. CONCLUSIONS: These studies demonstrate a reliable, noninvasive diagnostic assay for measurement of reticulated platelets in whole blood and provide a baseline for assessment of the clinical utility of the assay.

Animals↗

PubMed2002

Use of the Cell-Dyn 3500 to predict leukemic cell lineage in peripheral blood of dogs and cats.

BACKGROUND: Morphology and cytochemistry are the foundation for classification of leukemias in dogs and cats. Advances in automated hematology instrumentation, immunophenotyping, cytogenetics, and molecular biology are significantly improving our ability to recognize and classify spontaneous myeloproliferative and lymphoproliferative disorders. OBJECTIVE: The purpose of this study was to assess the utility of flow cytometry-based light scatter patterns provided by the Cell-Dyn 3500 (CD3500) automated hematology analyzer to predict the lineage of leukemic cells in peripheral blood of dogs and cats. METHODS: Leukemic cells from 15 dogs and 6 cats were provisionally classified using an algorithm based on the CD3500 CBC output data and were subsequently phenotyped by enzyme cytochemistry, immunocytochemistry, indirect flow cytometry, and analysis of antigen receptor gene rearrangement. RESULTS: The algorithm led to correct predictions regarding the ontogeny of the leukemic cells (erythroid/megakaryocytic potential, myeloid leukemia, monocytic leukemia, chronic granulocytic leukemia, lymphoid leukemia) in 19/21 animals. Mismatches in the WBC impedance count and the WBC optical count in conjunction with microscopic assessment of blasts in the blood were useful for predicting myeloproliferative disorders with erythroid or megakaryocytic potential. The leukocyte light scatter patterns enabled distinction among myeloid leukemias (represented by acute myelomonocytic leukemia, acute monocytic leukemia, chronic granulocytic leukemia) and lymphocytic leukemias (including acute and chronic lymphocytic leukemias). One case of acute lymphocytic leukemia was misidentified as chronic lymphocytic leukemia. CONCLUSIONS: Algorithmic analyses can be applied to data generated by the CD3500 to predict the ontogeny of leukemic cells in the peripheral blood of dogs and cats. This rapid and quantitative technique may be used to improve diagnostic decisions, expand therapeutic choices, and increase prognostic accuracy.

Algorithms↗

PubMed2002

Expression of fatty acid binding proteins inhibits lipid accumulation and alters toxicity in L cell fibroblasts.

High levels of saturated, branched-chain fatty acids are deleterious to cells and animals, resulting in lipid accumulation and cytotoxicity. Although fatty acid binding proteins (FABPs) are thought to be protective, this hypothesis has not previously been examined. Phytanic acid (branched chain, 16-carbon backbone) induced lipid accumulation in L cell fibroblasts similar to that observed with palmitic acid (unbranched, C(16)): triacylglycerol >> free fatty acid > cholesterol > cholesteryl ester >> phospholipid. Although expression of sterol carrier protein (SCP)-2, SCP-x, or liver FABP (L-FABP) in transfected L cells reduced [(3)H]phytanic acid uptake (57-87%) and lipid accumulation (21-27%), nevertheless [(3)H]phytanic acid oxidation was inhibited (74-100%) and phytanic acid toxicity was enhanced in the order L-FABP >> SCP-x > SCP-2. These effects differed markedly from those of [(3)H]palmitic acid, whose uptake, oxidation, and induction of lipid accumulation were not reduced by L-FABP, SCP-2, or SCP-x expression. Furthermore, these proteins did not enhance the cytotoxicity of palmitic acid. In summary, intracellular FABPs reduce lipid accumulation induced by high levels of branched-chain but not straight-chain saturated fatty acids. These beneficial effects were offset by inhibition of branched-chain fatty acid oxidation that correlated with the enhanced toxicity of high levels of branched-chain fatty acid.

Acetyl-CoA C-Acetyltransferase↗

PubMed2002

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

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.

Adrenocorticotropic Hormone↗

PubMed2002

Effect of antalarmin, a novel corticotropin-releasing hormone antagonist, on the dynamic function of the preterm ovine fetal hypothalamo-pituitary-adrenal axis.

This study describes the effect of antalarmin on basal and stimulated activity of the hypothalamo-pituitary-adrenal (HPA) axis function in the late gestation ovine fetus. Fetuses received antalarmin (15 mg/h i.v.) or vehicle (cremophor El 50% in ethanol) from day 130 gestational age. Antalarmin infusion did not significantly affect immunoreactive corticotropin (ir-ACTH) concentrations, although there was a tendency for ir-ACTH to be lower and cortisol concentrations were lower in the antalarmin-treated fetuses (p < 0.01). The ir-ACTH response to corticotropin-releasing hormone (CRH) challenge was attenuated (p < 0.05) in the antalarmin-treated fetuses, but neither antalarmin- nor vehicle-treated fetuses had significant cortisol responses to CRH. The ir-ACTH response to hypoxia was diminished (p < 0.05) in the antalarmin-treated fetuses while the cortisol responses of antalarmin- and vehicle-treated fetuses were indistinguishable. Deconvolution analysis revealed no effect of antalarmin treatment on ir-ACTH secretory dynamics. In contrast, antalarmin decreased (p < 0.05) basal, mean and integrated cortisol. The plasma cortisol responses of antalarmin- and vehicle-treated fetuses to exogenous ACTH(1-24) were indistinguishable. These data indicate that, while antalarmin inhibits CRH- and stress-induced ir-ACTH secretion, basal ir-ACTH secretion may be less affected by antalarmin treatment. Paradoxically, cortisol secretion is impaired by antalarmin infusion, although adrenal responsiveness to ACTH is not impaired. These results confirm a role for CRH in stress-induced ACTH secretion in the ovine fetus, though its role in the regulation of basal ACTH and cortisol secretion is unclear.

Adrenal Glands↗