A novel technique for measuring hypothalamic and pituitary hormone secretion rates from collection of pituitary venous effluent in the normal horse

1987 ◽  
Vol 113 (2) ◽  
pp. 183-192 ◽  
Author(s):  
C. H. G. Irvine ◽  
S. L. Alexander
Keyword(s):  
Hormone Secretion ◽  
Pituitary Hormones ◽  
Blood Collection ◽  
Pituitary Hormone ◽  
Blood Samples ◽  
Novel Technique ◽  
Time Period ◽  
Normal Functional ◽  
Gonadotrophin Releasing Hormone ◽  
Secretion Rates

ABSTRACT We have described a novel technique for collecting pituitary venous effluent in the horse by placing a cannula in the intercavernous sinus close to the outlet of the pituitary veins using a venous pathway unique to equids. Cannula placement and blood collection are carried out painlessly in fully conscious, ambulatory, unstressed animals. There is no interference to hypothalamic, pituitary or target organ function. The blood collected contains readily measurable concentrations of gonadotrophin-releasing hormone, and LH concentrations which can be up to 40 times those in concurrent peripheral blood samples. Four millilitre blood samples, a quantity which permits simultaneous measurement of many hypothalamic and pituitary hormones, can be collected at 2-min intervals for several days. Intercavernous sinus blood flow can be calculated allowing secretion rates of hypothalamic and pituitary hormones to be determined for any time-period. This model is uniquely useful for investigating the normal functional characteristics of several neuroendocrine and endocrine systems. J. Endocr. (1987) 113, 183–192

A comparison of the dynamics of secretion of human growth hormone and LH pulses

1988 ◽  
Vol 118 (2) ◽  
pp. 339-345 ◽  
Author(s):  
R. P. McIntosh ◽  
J. E. A. McIntosh ◽  
L. Lazarus
Keyword(s):  
Growth Hormone ◽  
Human Growth ◽  
Pituitary Hormones ◽  
Hypothalamic Stimulation ◽  
Target Organ ◽  
Pituitary Hormone ◽  
Hormone Release ◽  
Blood Samples ◽  
Gonadotrophin Releasing Hormone ◽  
Stimulation Current

ABSTRACT Patterns of hypothalamic stimulation causing pituitary hormone release cannot be studied directly in humans; one possible approach is to make inferences from the nature of the response of the target organ as revealed by patterns of pituitary hormones in blood. Replicated, precise assay of LH in frequently sampled blood of women at differing stages of the menstrual cycle has demonstrated previously that secretion of this hormone is compatible with a model of discrete, instantaneous episodes of LH output, which are assumed to be stimulated by isolated bursts of increased stimulatory hypothalamic gonadotrophin-releasing hormone. However, similarly detailed measurements of the dynamic secretion patterns of GH in women reported here, revealed much slower rates of increase of GH concentrations (median time to maximum concentration 38 min) in comparison with LH (13 min) assayed in the same blood samples. These rise rates of GH were uncorrelated with the final amplitude of the peak and were observably discontinuous in half the peaks. Simultaneous i.v. injection of a bolus of mixed GRF and GnRH produced similar dynamics of pituitary release of GH and LH. Thus differences in patterns of natural release of the two hormones appear to be contributed to by differences in the modes of hypothalamic stimulation. Current understanding of control of GH release in animal models suggests that the slow-rising, frequently discontinuous natural peaks of GH in human blood are likely to be caused by interaction between the withdrawal of inhibitory hypothalamic somatostatin and the increased secretion of stimulatory GRF. J. Endocr. (1988) 118, 339-345

Vasopressin as a neuroendocrine regulator of anterior pituitary hormone secretion

1993 ◽  
Vol 129 (6) ◽  
pp. 489-496 ◽  
Author(s):  
Andreas Kjær
Keyword(s):  
Arginine Vasopressin ◽  
Mode Of Action ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Pituitary Hormones ◽  
Pituitary Hormone ◽  
Anterior Pituitary Hormones ◽  
Anterior Pituitary Hormone

Secretion of the anterior pituitary hormones adrenocorticotropin (ACTH), β-endorphin and prolactin (PRL) is complex and involves a variety of factors. This review focuses on the involvement of arginine-vasopressin (AVP) in neuroendocrine regulation of these anterior pituitary hormones with special reference to receptor involvement, mode of action and origin of AVP. Arginine-vasopressin may act via at least two types of receptors: V1− and V2−receptors, where the pituitary V1−receptor is designated V1b. The mode of action of AVP may be mediating, i.e. anterior pituitary hormone secretion is transmitted via release of AVP, or the mode of action may be permissive, i.e. the presence of AVP at a low and constant level is required for anterior pituitary hormones to be stimulated. Under in vivo conditions, the AVP-induced release of ACTH and β-endorphin is mainly mediated via activation of hypothalamic V1− receptors, which subsequently leads to the release of corticotropin-releasing hormone. Under in vitro conditions, the AVP-stimulated release of ACTH and β-endorphin is mediated via pituitary V1b− receptors. The mode of action of AVP in the ACTH and β-endorphin response to stress and to histamine, which is involved in stress-induced secretion of anterior pituitary hormones, is mediating (utilizing V1− receptors) as well as permissive (utilizing mainly V1− but also V2−receptors). The AVP-induced release of PRL under in vivo conditions is conveyed mainly via activation of V1−receptors but V2−receptors and probably additional receptor(s) may also play a role. In stress- and histamine induced PRL secretion the role of AVP is both mediating (utilizing V1 −receptors) and permissive (utilizing both V1− and V2− receptors). Arginine-vasopressin may be a candidate for the PRL-releasing factor recently identified in the posterior pituitary gland. Arginine-vasopressin of both magno- and parvocellular origin may be involved in the regulation of anterior pituitary hormone secretion and may reach the corticotrophs and the lactotrophs via three main routes: the peripheral circulation, the long pituitary portal vessels or the short pituitary portal vessels.

Estimation of pituitary secretion rate during the reproductive cycle of sheep

1990 ◽  
Vol 114 (2) ◽  
pp. 213-218
Author(s):  
K. S. Lindsay ◽  
I. R. Fleet ◽  
D. E. Walters ◽  
R. B. Heap
Keyword(s):  
Blood Flow ◽  
Reproductive Cycle ◽  
Hormone Secretion ◽  
Pituitary Hormone ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone ◽  
Pituitary Secretion ◽  
Conscious Sheep ◽  
Cephalic Blood Flow ◽  
Secretion Rates

SUMMARYA technique has been developed for the measurement of pituitary hormone secretion rates in conscious sheep. The technique involves the continuous and simultaneous sampling of blood from the carotid artery and jugular vein and the measurement of cephalic blood flow by an indicator dilution technique. Veno-arterial differences in hormone concentrations multiplied by cephalic blood flow gave average secretion rates which were measured after single or repeated large doses of luteinizing hormone releasing hormone (LHRH) and thyrotrophin-releasing hormone (TRH) at various times in the reproductive cycle.

The effect of a potent gonadotrophin-releasing hormone antagonist on ovarian secretion of oestradiol, inhibin and androstenedione and the concentration of LH and FSH during the follicular phase of the sheep oestrous cycle

1990 ◽  
Vol 126 (3) ◽  
pp. 377-384 ◽  
Author(s):  
B. K. Campbell ◽  
A. S. McNeilly ◽  
H. M. Picton ◽  
D. T. Baird
Keyword(s):  
Gnrh Antagonist ◽  
Venous Blood ◽  
Hormone Secretion ◽  
Experimental Period ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Blood Samples ◽  
Releasing Hormone ◽  
Inhibitory Feedback ◽  
Gonadotrophin Releasing Hormone

ABSTRACT By selective removal and replacement of LH stimulation we sought to examine the relative importance of inhibin and oestradiol in controlling FSH secretion, and the role of LH in the control of ovarian hormone secretion, during the follicular phase of the oestrous cycle. Eight Finn–Merino ewes which had one ovary removed and the other autotransplanted to a site in the neck were given two injections of a gonadotrophin-releasing hormone (GnRH) antagonist (50 μg/kg s.c.) in the follicular phase of the cycle 27 h and 51 h after luteal regression had been induced by cloprostenol (100 μg i.m.). Four of the ewes received, in addition, i.v. injections of 2·5 μg LH at hourly intervals for 23 h from 42 to 65 h after GnRH antagonist treatment. Ovarian jugular venous blood samples were taken at 10-min intervals for 3 h before and 5 h after the injection of antagonist (24–32 h after cloprostenol) and from 49 to 53 h after antagonist (74–78 h after cloprostenol). Additional blood samples were taken at 4-h intervals between the periods of intensive blood sampling. The GnRH antagonist completely inhibited endogenous pulsatile LH secretion within 1 h of injection. This resulted in a marked decrease in the ovarian secretion of oestradiol and androstenedione (P<0·001), an effect that was reversible by injection of exogenous pulses of LH (P<0·001). The pattern of ovarian inhibin secretion was episodic, but removal or replacement of stimulation by LH had no effect on the pattern or level of inhibin secretion. Peripheral concentrations of FSH rose (P<0·01) within 20 h of administration of the antagonist and these increased levels were maintained in ewes given no exogenous LH. In ewes given LH, however, FSH levels declined within 4 h of the first LH injection and by the end of the experimental period the levels of FSH were similar to those before administration of antagonist (P<0·01). These results confirm that ovarian oestradiol and androstenedione secretion, but not inhibin secretion, is under the acute control of LH. We conclude that oestradiol, and not inhibin, is the major component of the inhibitory feedback loop controlling the pattern of FSH secretion during the follicular phase of the oestrous cycle in ewes. Journal of Endocrinology (1990) 126, 377–384

Toward Multifactorial Hypothalamic Regulation of Anterior Pituitary Hormone Secretion

Physiology ◽  
1999 ◽  
Vol 14 (2) ◽  
pp. 54-58
Author(s):  
W. R. Crowley
Keyword(s):  
Neuropeptide Y ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Pituitary Hormones ◽  
Gonadotropin Releasing Hormone ◽  
Pituitary Hormone ◽  
Anterior Pituitary Hormone ◽  
Hypothalamic Hormones ◽  
Hypothalamic Regulation ◽  
Hypophysial Portal

The hypothalamus regulates the secretion of anterior pituitary hormones via release of releasing hormones into the hypophysial portal vasculature. Additional neuromessengers act at the pituitary to modulate responses to the hypothalamic hormones. For example, neuropeptide Y enhances the effect of gonadotropin-releasing hormone and the response to the prolactin-inhibiting hormone dopamine.

A noninvasive measure of negative-feedback strength, approximate entropy, unmasks strong diurnal variations in the regularity of LH secretion

2007 ◽  
Vol 293 (5) ◽  
pp. E1409-E1415 ◽  
Author(s):  
Peter Y. Liu ◽  
Ali Iranmanesh ◽  
Daniel M. Keenan ◽  
Steven M. Pincus ◽  
Johannes D. Veldhuis
Keyword(s):  
Time Series ◽  
Negative Feedback ◽  
Hormone Secretion ◽  
High Sensitivity ◽  
Approximate Entropy ◽  
Pituitary Hormones ◽  
Pituitary Hormone ◽  
Model Free ◽  
General Utility ◽  
Feedback Strength

The secretion of anterior-pituitary hormones is subject to negative feedback. Whether negative feedback evolves dynamically over 24 h is not known. Conventional experimental paradigms to test this concept may induce artifacts due to nonphysiological feedback. These limitations might be overcome by a noninvasive methodology to quantify negative feedback continuously over 24 h without disrupting the axis. The present study exploits a recently validated model-free regularity statistic, approximate entropy (ApEn), which monitors feedback changes with high sensitivity and specificity (both >90%; Pincus SM, Hartman ML, Roelfsema F, Thorner MO, Veldhuis JD. Am J Physiol Endocrinol Metab 273: E948–E957, 1999). A time-incremented moving window of ApEn was applied to LH time series obtained by intensive (10-min) blood sampling for four consecutive days (577 successive measurements) in each of eight healthy men. Analyses unveiled marked 24-h variations in ApEn with daily maxima (lowest feedback) at 1100 ± 1.7 h (mean ± SE) and minima (highest feedback) at 0430 ± 1.9 h. The mean difference between maximal and minimal 24-h LH ApEn was 0.348 ± 0.018, which differed by P < 0.001 from all three of randomly shuffled versions of the same LH time series, simulated pulsatile data and assay noise. Analyses artificially limited to 24-h rather than 96-h data yielded reproducibility coefficients of 3.7–9.0% for ApEn maxima and minima. In conclusion, a feedback-sensitive regularity statistic unmasks strong and consistent 24-h rhythmicity of the orderliness of unperturbed pituitary-hormone secretion. These outcomes suggest that ApEn may have general utility in probing dynamic mechanisms mediating feedback in other endocrine systems.

scholarly journals Expression and thyroid hormone regulation of annexins in the anterior pituitary

2007 ◽  
Vol 195 (3) ◽  
pp. 385-392 ◽  
Author(s):  
Jens Mittag ◽  
Wiebke Oehr ◽  
Heike Heuer ◽  
Tuula Hämäläinen ◽  
Bent Brachvogel ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Mrna Expression ◽  
Hormone Secretion ◽  
Pituitary Hormones ◽  
Pituitary Hormone ◽  
Dependent Manner ◽  
Hormone Regulation ◽  
Wild Type ◽  
Transcript Levels ◽  
Redundant Functions

Due to their property to bind to phospholipids in a Ca2+-dependent manner, proteins of the annexin superfamily are involved in many membrane-related events and thus in various forms of physiological and pathological processes. We were therefore interested in analyzing the mRNA expression of the annexins in the severely disorganized pituitaries of the athyroid Pax8−/− mice in comparison with that of control animals. In neither condition was mRNA expression of the annexins A3, A7, A8, A9, A11, and A13 detectable. The annexins A2, A4, and A6 were equally expressed in wild-type and Pax8−/− mice. Transcript levels of A1 and A10 were highly increased and those of A5 were significantly decreased in the athyroid mutants compared with controls. Treatment of Pax8−/− mice with physiological doses of thyroxine for 3 days normalized the mRNA expression of A1, A5, and A10 indicating that the expression of these annexins is directly regulated by thyroid hormone (TH). Since A5 exhibits by far the highest transcript levels of all annexins in the pituitary and its regulation by TH could be also confirmed at the protein level, we analyzed the mRNA expression of pituitary hormones in A5−/− mice. In these mutants, only the β-FSH mRNA expression was found to be significantly reduced, while the mRNA expression levels of the other pituitary hormones were not altered. These results support the concept that annexins might serve important albeit redundant functions as modulators of pituitary hormone secretion.

scholarly journals Pituitary Actions of EGF on Gonadotropins, Growth Hormone, Prolactin and Somatolactins in Grass Carp

Biology ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 279
Author(s):  
Qiongyao Hu ◽  
Qinbo Qin ◽  
Shaohua Xu ◽  
Lingling Zhou ◽  
Chuanhui Xia ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Mrna Expression ◽  
Grass Carp ◽  
Hormone Secretion ◽  
Pituitary Hormones ◽  
Vital Role ◽  
Pituitary Hormone ◽  
Pituitary Cells ◽  
Neurokinin Receptor

In mammals, epidermal growth factor (EGF) plays a vital role in both pituitary physiology and pathology. However, the functional role of EGF in the regulation of pituitary hormones has rarely reported in teleost. In our study, using primary cultured grass carp pituitary cells as an in vitro model, we examined the effects of EGF on pituitary hormone secretion and gene expression as well as the post-receptor signaling mechanisms involved. Firstly, we found that EGF significantly reduced luteinizing hormone (LHβ) mRNA expression via ErbB1 coupled to ERK1/2 pathway, but had no effect on LH release in grass carp pituitary cells. Secondly, the results showed that EGF was effective in up-regulating mRNA expression of growth hormone (GH), somatolactin α (SLα) and somatolactin β (SLβ) via ErbB1 and ErbB2 and subsequently coupled to MEK1/2/ERK1/2 and PI3K/Akt/mTOR pathways, respectively. However, EGF was not effective in GH release in pituitary cells. Thirdly, we found that EGF strongly induced pituitary prolactin (PRL) release and mRNA expression, which was mediated by ErbB1 and subsequent stimulation of MEK1/2/ERK1/2 and PI3K/Akt/mTOR pathways. Interestingly, subsequent study further found that neurokinin B (NKB) significantly suppressed EGF-induced PRL mRNA expression, which was mediated by neurokinin receptor (NK2R) and coupled to AC/cAMP/PKA signal pathway. These results suggested that EGF could differently regulate the pituitary hormones expression in grass carp pituitary cells.

scholarly journals Pituitary volume in patients with Primary Empty Sella and clinical relevance to pituitary hormone secretion: A retrospective single center study

2021 ◽  
Vol 17 ◽  
Author(s):  
Gamze Akkus ◽  
Sinan Sözütok ◽  
Fulya Odabaş ◽  
Bilen Onan ◽  
Mehtap Evran ◽  
...  
Keyword(s):  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Sella Turcica ◽  
Volume Measurement ◽  
Pituitary Hormones ◽  
Empty Sella ◽  
Pituitary Hormone ◽  
Pituitary Dysfunction ◽  
Volume Measurements ◽  
Primary Empty Sella

Background: According to neuroradiological findings, empty sella seems to be deprived of pituitary tissue in sella turcica. Changing size of the pituitary volume is closely related to the occurrence of primary empty sella. The aim of the study is to determine pituitary dysfunction in patients with partial or total primary empty sella and the significance of pituitary volume measurements in these patients. Methods: This study was designed retrospectively. 67 patients (55 females, 12 males) diagnosed with primary empty sella syndrome between the years of 2015-2019 were included in the study. Patients were divided into two groups: partial (PES) and total (TES) empty sella by magnetic resonance imaging (MRI). Basal anterior pituitary and its hormones were assessed. We also included 26 healthy control subjects (19 females, 7 males) to compare the differences in pituitary volumes. Volumes were measured by using Osirix Dicom Viewer ( Pixmeo SARL, Geneve, Swiss) in 3.0 Tesla scanner MRI. Results: 82.1% (n=55) of all patients were PES and the others were (n=12) TES. Hypopituitarism, known as one or more pituitary hormones deficiency, was found in 12 patients (17.9%). While 9 of them had total PES, the others had partial PES. Secondary adrenal insufficiency and gonadotropin deficiency were more prevalent in patients with TES. Mean volume measurements of patients with TES, PES and healthy subjects were 0.23±0.17, 0.35±0.15, 0.54±0.17 cm3, respectively. Except for IGF1 values (p=0.026), there was not any significant correlation found between the anterior pituitary hormones and volume measurements. Conclusion: Although volume measurement has helped in the diagnosis of pituitary empty sella (partial or total), it does not seem to have any significant correlation with pituitary secretory function.

Stability of antioxidant vitamins in whole human blood during overnight storage at 4°C and frozen storage up to 6 months

2018 ◽  
Vol 88 (3-4) ◽  
pp. 151-157 ◽  
Author(s):  
Scott W. Leonard ◽  
Gerd Bobe ◽  
Maret G. Traber
Keyword(s):  
Ascorbic Acid ◽  
Whole Blood ◽  
Healthy Subjects ◽  
Frozen Storage ◽  
Blood Collection ◽  
Plasma Samples ◽  
Optimal Conditions ◽  
Plasma Ascorbic Acid ◽  
Blood Samples ◽  
Sample Handling

Abstract. To determine optimal conditions for blood collection during clinical trials, where sample handling logistics might preclude prompt separation of erythrocytes from plasma, healthy subjects (n=8, 6 M/2F) were recruited and non-fasting blood samples were collected into tubes containing different anticoagulants (ethylenediaminetetra-acetic acid (EDTA), Li-heparin or Na-heparin). We hypothesized that heparin, but not EDTA, would effectively protect plasma tocopherols, ascorbic acid, and vitamin E catabolites (α- and γ-CEHC) from oxidative damage. To test this hypothesis, one set of tubes was processed immediately and plasma samples were stored at −80°C, while the other set was stored at 4°C and processed the following morning (~30 hours) and analyzed, or the samples were analyzed after 6 months of storage. Plasma ascorbic acid, as measured using HPLC with electrochemical detection (LC-ECD) decreased by 75% with overnight storage using EDTA as an anticoagulant, but was unchanged when heparin was used. Neither time prior to processing, nor anticoagulant, had any significant effects upon plasma α- or γ-tocopherols or α- or γ-CEHC concentrations. α- and γ-tocopherol concentrations remained unchanged after 6 months of storage at −80°C, when measured using either LC-ECD or LC/mass spectrometry. Thus, refrigeration of whole blood at 4°C overnight does not change plasma α- or γ-tocopherol concentrations or their catabolites. Ascorbic acid is unstable in whole blood when EDTA is used as an anticoagulant, but when whole blood is collected with heparin, it can be stored overnight and subsequently processed.

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