A carnivore species (Canis familiaris) expresses circadian melatonin rhythm in the peripheral blood and melatonin receptors in the brain

1994 ◽  
Vol 131 (2) ◽  
pp. 191-200 ◽  
Author(s):  
Bojidar Stankov ◽  
Morten Møller ◽  
Valeria Lucini ◽  
Simona Capsoni ◽  
Franco Fraschini
Keyword(s):  
Peripheral Blood ◽  
Binding Sites ◽  
Specific Binding ◽  
Canis Familiaris ◽  
Melatonin Receptors ◽  
Pars Tuberalis ◽  
Pars Distalis ◽  
Melatonin Rhythm ◽  
Carnivore Species ◽  
The Brain

Stankov B, Møller, M, Lucini V, Capsoni S, Fraschini F. A carnivore species (Canis familiaris) expresses circadian melatonin rhythm in the peripheral blood and melatonin receptors in the brain. Eur J Endocrinol 1994;131:191–200. ISSN 0804–4643 Dogs kept under controlled photoperiodic conditions of 12 h light and 12 h dark expressed a clear diurnal melatonin rhythm in the peripheral blood, with a swift peak restricted to the late part of the scotophase. The highest density of high-affinity, G-protein-linked 2-[125I]iodomelatonin binding sites was found in the pars tuberalis of the pituitary gland. Binding sites were found also in the pars distalis, and light microscopy/high-resolution autoradiography showed that binding was located exclusively over the chromophobe and basophilic cells forming the adenopituitary zona tuberalis, well developed in this species, and extending into the gland as a continuation of pars tuberalis. Cords of basophilic cells located in the pars distalis proper also expressed high receptor density. The eosinophils in the adenohypophysis and the neural lobe were devoid of binding. Heavily labeled were the external laminar and the mitral cell layers of the olfactory bulbs, but no binding was detected in the filae nervi olfactorii or tractus olfactorius. The hypothalamic suprachiasmatic nuclei were discernible clearly. Quantitative autoradiography inhibition experiments revealed that the apparent melatonin inhibitory constant (ic50) in all those areas was around 0.1 nmol/l, which is a physiologically appropriate value considering the peripheral blood melatonin levels. Co-incubation with guanosine 5′-O-(3-thiotriphosphate) (GTPΓS) led to a consequential decrease in the binding density. The specific binding observed in other areas (hippocampus, frontal, parietal, occipital cortex and cerebellum) was rather weak, diffuse and could not be attributed to a particular layer; the apparent ic50 for melatonin was about 1 μmol/l, and co-incubation with GTPΓS did not modify the binding density. Collectively, these data show that the dog posesses all the prerequisites for an efficient network adapted to photoperiodic time measurements. A circadian melatonin signal in the peripheral blood and an apparently functional readout receptor system located in key positions within the brain are both present in this species. Bojidar Stankov, Chair of Chemotherapy, Department of Pharmacology, University of Milan, 32 Via Vanvitelli, 20129 Milano, Italy

The development of melatonin-binding sites in the ovine fetus

1994 ◽  
Vol 142 (3) ◽  
pp. 475-484 ◽  
Author(s):  
R J A Helliwell ◽  
L M Williams
Keyword(s):  
G Protein ◽  
Binding Sites ◽  
Early Stage ◽  
Specific Binding ◽  
Melatonin Receptors ◽  
Pars Tuberalis ◽  
Dependent Manner ◽  
Pars Distalis ◽  
Specific Expression ◽  
Fetal Sheep

Abstract The pineal hormone, melatonin, is important in the timing of seasonal reproduction in the sheep. Melatonin of maternal origin readily crosses the placenta; its function in the fetal sheep is, however, unclear. To gain an insight into the role of melatonin in ovine development we have identified specific melatonin receptors throughout gestation using 2-[125I]iodomelatonin and quantitative in vitro autoradiography. Specific binding was found at the earliest time studied at 30 days of gestation, over the developing thyroid (term=145 days). At 31 days of gestation specific labelling was found over the thyroid and pituitary glands, the spinal nerves, nasal cavity and developing bronchi. This binding was diminished by over 50% in the presence of 10−4 m GTPγS (an analogue of guanosine triphosphate) indicating that the 2-[125I]iodomelatonin binding at this early stage of gestation represents a receptor coupled to a regulatory G-protein. By 40 days of gestation specific binding was found over the nasal epithelium, cochlear epithelium, regions of the brain, especially the hind brain and the vestibulocochlear and glossopharyngeal nerves, and both the pars distalis and pars tuberalis of the pituitary. As gestation proceeded, labelling over the pars distalis appeared to become more scattered in nature while that on the pars tuberalis remained consistent. Saturation studies of both the neuronal and pituitary binding sites at 121 days of gestation and in the newborn lamb revealed a single class of high-affinity binding sites with Kd values in the picomolar range. Also at 121 days of gestation, binding over the fetal pars tuberalis was diminished in a dose-dependent manner by GTPγS, again confirming that specific binding is indicative of a receptor coupled to a regulatory G-protein. These data demonstrate a potential for sensitivity to melatonin from early in gestation, as well as the developmentally specific expression of the melatonin receptor in certain tissues, and suggest a wider role for melatonin in ovine fetal development than previously considered. Journal of Endocrinology (1994) 142, 475–484

Melatonin-binding sites in the rat brain and pituitary mapped by in-vitro autoradiography

1989 ◽  
Vol 3 (1) ◽  
pp. 71-75 ◽  
Author(s):  
L. M. Williams
Keyword(s):  
Rat Brain ◽  
Binding Sites ◽  
Area Postrema ◽  
Specific Binding ◽  
Melatonin Receptors ◽  
Pars Tuberalis ◽  
Lower Affinity ◽  
High Affinity ◽  
In Vitro Autoradiography

ABSTRACT Using picomolar concentrations of [125I]iodomelatonin and in-vitro autoradiography, specific melatonin-binding sites have been mapped in the rat brain and pituitary. Using this same technique, high-affinity melatonin receptors had previously been identified in the suprachiasmatic nucleus (SCN) and median eminence regions of the rat hypothalamus. The presence of melatonin binding in the SCN has been confirmed, but the second area of binding has been identified as the pars tuberalis of the pituitary, and a completely novel area of binding is also reported in the area postrema. The existence of lower affinity melatonin receptors in the rat brain was also investigated using in-vitro autoradiography and higher concentrations of [125I]iodomelatonin. No further sites of specific binding were, however, disclosed.

Characterization of melatonin receptors in the ram pars tuberalis: influence of light

1990 ◽  
Vol 123 (5) ◽  
pp. 557-562 ◽  
Author(s):  
Jean Pelletier ◽  
Bertrand Castro ◽  
Georges Roblot ◽  
Renée Wylde ◽  
Marie-Madeleine de Reviers
Keyword(s):  
Median Eminence ◽  
Binding Sites ◽  
Melatonin Receptors ◽  
Scatchard Analysis ◽  
Pars Tuberalis

Abstract. The present study was conducted to assess the binding of [125I]melatonin to frozen unfixed sections of pars tuberalis/median eminence tissue from Ile-de-France rams exposed or not exposed to light before slaughter. The specificity of [125I]melatonin binding to the pars tuberalis tissue was revealed by autoradiography and the magnitude of binding as related to the pars tuberalis area was determined after incubation and counting of pars tuberalis/median eminence sections. Subsequent studies with sections incubated with [125I]melatonin indicated that 1. the binding sites were saturable; 2. binding was stable for 24 h at 20°C, but unstable at 28 or 37°C; 3. melatonin and [12 7I]melatonin had a similar potency to compete with [125I]melatonin for binding sites, whereas other ligands such as serotonin or N-acetylserotonin were devoid of activity, and 4. by Scatchard analysis, the constant affinity Ka was found to be high in the 1010 l/mol range. Rams exposed to light throughout the night prior to slaughter presented a significant increase in the apparent number of [125I]melatonin binding sites in comparison to animals maintained under darkness (2.25±0.30 vs 1.01±0.17 fmol/mm2 pars tuberalis, p<0.01), whereas Ka values were similar in both groups. These results indicate the presence of true melatonin receptors in the pars tuberalis of the ram. Furthermore, they suggest that their apparent number is light-dependent.

scholarly journals Specific Binding Sites for Endothelin in the Brain, Spinal Cord, Heart and Kidney

1990 ◽  
Vol 31 (4) ◽  
pp. 567-567
Author(s):  
Masami Niwa ◽  
Tsutomu Kawaguchi ◽  
Tetsu Maeda ◽  
Hidefumi Yamasaki ◽  
Masaki Kurihara ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Binding Sites ◽  
Specific Binding ◽  
Specific Binding Sites ◽  
The Brain

scholarly journals Molecular economy of nature with two thyrotropins from different parts of the pituitary: pars tuberalis thyroid-stimulating hormone and pars distalis thyroid-stimulating hormone

2021 ◽  
Vol 17 (1) ◽  
pp. 189-195
Author(s):  
Sibel Ertek
Keyword(s):  
Pineal Gland ◽  
Light Stimulus ◽  
Peripheral Circulation ◽  
Thyroid Stimulating Hormone ◽  
Breeding Period ◽  
Pars Tuberalis ◽  
Pars Distalis ◽  
Subunit Expression ◽  
The Brain ◽  
Stimulating Hormone

Thyrotropin (TSH) is classically known to be regulated by negative feedback from thyroid hormones and stimulated by thyrotropin-releasing hormone (TRH) from the hypothalamus. At the end of the 1990s, studies showed that thyrotroph cells from the pars tuberalis (PT) did not have TRH receptors and their TSH regulation was independent from TRH stimulation. Instead, PT-thyrotroph cells were shown to have melatonin-1 (MT-1) receptors and melatonin secretion from the pineal gland stimulates TSH- subunit formation in PT. Electron microscopy examinations also revealed some important differences between PT and pars distalis (PD) thyrotrophs. PT-TSH also have low bioactivity in the peripheral circulation. Studies showed that they have different glycosylations and PT-TSH forms macro-TSH complexes in the periphery and has a longer half-life. Photoperiodism affects LH levels in animals via decreased melatonin causing increased TSH- subunit expression and induction of deiodinase-2 (DIO-2) in the brain. Mammals need a light stimulus carried into the suprachiasmatic nucleus (which is a circadian clock) and then transferred to the pineal gland to synthesize melatonin, but birds have deep brain receptors and they are stimulated directly by light stimuli to have increased PT-TSH, without the need for melatonin. Photoperiodic regulations via TSH and DIO 2/3 also have a role in appetite, seasonal immune regulation, food intake and nest-making behaviour in animals. Since humans have no clear seasonal breeding period, such studies as recent ‘’domestication locus’’ studies in poultry are interesting. PT-TSH that works like a neurotransmitter in the brain may become an important target for future studies about humans.

Daily Rhythms of Melatonin Binding Sites in the Rat Pars tuberalis and Suprachiasmatic Nuclei; Evidence for a Regulation of Melatonin Receptors by Melatonin Itself

1993 ◽  
Vol 57 (1) ◽  
pp. 120-126 ◽  
Author(s):  
François Gauer ◽  
Mireille Masson-Pévet ◽  
Debra Jean Skene ◽  
Berthe Vivien-Roels ◽  
Paul Pévet
Keyword(s):  
Binding Sites ◽  
Melatonin Receptors ◽  
Pars Tuberalis ◽  
Suprachiasmatic Nuclei ◽  
Daily Rhythms

scholarly journals The binding of ouabain to normal and chronic lymphocytic leukemic lymphocytes

Blood ◽  
1979 ◽  
Vol 54 (5) ◽  
pp. 994-1000
Author(s):  
JS Wiley ◽  
N Kraft ◽  
IA Cooper
Keyword(s):  
Peripheral Blood ◽  
Binding Sites ◽  
Specific Binding ◽  
Lymphocytic Leukemia ◽  
Ouabain Binding ◽  
Normal Peripheral Blood ◽  
Binding Characteristics ◽  
Specific Binding Sites ◽  
Equilibrium Binding ◽  
The Difference

The binding of the cardiac glycoside, ouabain, to cells had been used to quantify the number of active cation pumps. In this study, lymphocytes were incubated with 3H-ouabain and the equilibrium binding analyzed for the maximal number of specific binding sites. Lymphocytes from normal peripheral blood bound 44,200 +/- 9920 molecules/cell, compared with 29,200 +/- 8370 molecules/cell for the lymphocytes of chronic lymphocytic leukemia (CLL) subjects. This difference was significant (p less than 0.01) and did not reflect a lower number of sites on B cells than T cells, since B-cell-enriched lymphocytes from normal peripheral blood showed the same ouabain binding characteristics as the standard T-cell-rich preparation. Although monocytes bind threefold more ouabain than lymphocytes, the small monocyte contamination (3.0%) in normal lymphocyte preparations could not account for the difference between normal and CLL. The fewer ouabain binding sites on CLL lymphocytes may reflect both their smaller size (by 10%) and lower mitotic activity compared with lymphocytes from normal peripheral blood.

The pars tuberalis of the hypophysis: a modulator of the pars distalis?

1992 ◽  
Vol 126 (4) ◽  
pp. 285-290 ◽  
Author(s):  
Werner H Wittkowski ◽  
Andreas H Schulze-Bonhage ◽  
Tobias M Böckers
Keyword(s):  
Close Contact ◽  
Melatonin Receptors ◽  
Portal System ◽  
Secretory Cells ◽  
Specific Cell ◽  
Pars Tuberalis ◽  
Pars Distalis ◽  
Functional Connection ◽  
Morphological Alterations ◽  
Functional Changes

The pineal hormone melatonin is known to influence circadian systems. Melatonin is also ascribed to mediate photoperiodic effects on the regulation of the hypothalamo-hypophyseal-gonadal axis. Other endocrine actions, especially a thyrotropic influence, have been postulated. Site and mechanism of action of melatonin, however, are still matters of speculation. In search of a functional cascade of (i) photoperiodic stimuli, (ii) their hormonal messenger melatonin, and (iii) endocrine targets, the pars tuberalis has gained a key position. The recent discovery and characterization of melatonin receptors located in the pars tuberalis of several species support such a functional significance. Earlier results point to a functional connection of the pars tuberalis with the pineal gland: the pars tuberalis is known for a pattern of differentiation distinctly different from other parts of the adenohypophysis. It contains a specific cell population with a morphology typical of peptide secreting cells. Like the hypothalamic nerve endings of the median eminence, they are in close contact with the primary plexus of the portal system. In contrast to secretory cells of the pars distalis, the specific cells of the pars tuberalis do not respond with morphological alterations to functional changes of peripheral endocrine glands. Yet, photoperiodic stimuli obviously influence morphology and functional activity of the pars tuberalis-specific cells. Investigations during recent years have led to the tentative conclusion that the pars tuberalis represents the hypophysial "receptor"for melatonin as the chemical messenger of photoperiodic stimuli. Depending on melatonin secretion pattern and melatonin receptivity, the pars tuberalis seems to modulate at least gonadotropic and thyrotropic activity of the pars distalis via a peptide hormone distributed in the pars distalis by the portal plexus. Such an intrahypophysial regulatory concept may explain the widespread actions of melatonin on endocrine targets.

scholarly journals The binding of ouabain to normal and chronic lymphocytic leukemic lymphocytes

Blood ◽  
1979 ◽  
Vol 54 (5) ◽  
pp. 994-1000 ◽  
Author(s):  
JS Wiley ◽  
N Kraft ◽  
IA Cooper
Keyword(s):  
Peripheral Blood ◽  
Binding Sites ◽  
Specific Binding ◽  
Lymphocytic Leukemia ◽  
Ouabain Binding ◽  
Normal Peripheral Blood ◽  
Binding Characteristics ◽  
Specific Binding Sites ◽  
Equilibrium Binding ◽  
The Difference

Abstract The binding of the cardiac glycoside, ouabain, to cells had been used to quantify the number of active cation pumps. In this study, lymphocytes were incubated with 3H-ouabain and the equilibrium binding analyzed for the maximal number of specific binding sites. Lymphocytes from normal peripheral blood bound 44,200 +/- 9920 molecules/cell, compared with 29,200 +/- 8370 molecules/cell for the lymphocytes of chronic lymphocytic leukemia (CLL) subjects. This difference was significant (p less than 0.01) and did not reflect a lower number of sites on B cells than T cells, since B-cell-enriched lymphocytes from normal peripheral blood showed the same ouabain binding characteristics as the standard T-cell-rich preparation. Although monocytes bind threefold more ouabain than lymphocytes, the small monocyte contamination (3.0%) in normal lymphocyte preparations could not account for the difference between normal and CLL. The fewer ouabain binding sites on CLL lymphocytes may reflect both their smaller size (by 10%) and lower mitotic activity compared with lymphocytes from normal peripheral blood.

scholarly journals Substance P receptors in rat spleen: characterization and autoradiographic distribution

Blood ◽  
1986 ◽  
Vol 68 (6) ◽  
pp. 1398-1401 ◽  
Author(s):  
CJ Wiedermann ◽  
K Sertl ◽  
CB Pert
Keyword(s):  
Substance P ◽  
Binding Sites ◽  
Marginal Zone ◽  
Specific Binding ◽  
Single Class ◽  
Ligand Selectivity ◽  
Tissue Sections ◽  
The Brain ◽  
Substance P Receptors ◽  
Red Pulp

Abstract The interaction of substance P with intact lymphatic tissue was quantified and autoradiographically visualized, using slide-mounted tissue sections of rat spleen. Radiolabeled substance P binds rapidly to an apparently single class of noninteracting high affinity sites (Kd = 2.4 nmol/L; Bmax = 9.4 fmol/mg protein). The ligand selectivity pattern suggests that substance P binding sites are similar to substance P receptors found in other tissues, including the brain, T lymphocytes, and macrophages. Substance P receptors are highly concentrated in the antigen-trapping spleen marginal zone, with low densities being found in the red pulp. No specific binding of radiolabel to T cell-dependent immunologic domains of the spleen is seen. The distribution of substance P receptors suggests that substance P is probably involved in the control of sensory functions of the immune system.

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