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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study reports the presence in AtT-20 corticotrophs of high affinity-low capacity receptors for arginine-vasopressin (AVP), whose binding capacity was considerably enhanced by the divalent metal ion nickel. These binding sites, when analyzed in the presence of nickel, showed high affinity for AVP, vasotocin and oxytocin, but recognized to a lesser extent the V2-agonist 1-deamino-AVP, as well as V1-antagonists. Surprisingly, AVP failed to alter secretion of proopiomelanocortin (POMC)-derived peptides from the cells or corticotropin-releasing factor (CRF)-induced cAMP synthesis, as reported in normal corticotrophs. Exposure of cells to CRF elicited an increase in mRNAPOMC levels, while, in contrast, AVP was without significant effect. It thus appears that in AtT-20 tumor cells, the AVP receptors are not coupled to either the biochemical or biological cellular response.
Mol Cell Endocrinol 1987 Oct
PMID:Evidence that AVP receptors in AtT-20 corticotrophs are not coupled to secretion of POMC-derived peptides. 282 11

We examined the effects of oxytocin on renal tubular epithelial LLC-PK1 cells. In cells loaded with Fura 2, we found that 1 microM oxytocin induced a rapid increase in cytosolic free [Ca2+]i from 120 nM to 250 nM within 12 sec. [Ca2+]i then decreased and leveled at 148 nM. Calcium was mobilized from intra- and extra-cellular sources. Oxytocin-induced calcium mobilization was dose dependent (EC50 between 5 and 30 nM). Oxytocin also stimulated calcium efflux which was blocked by the selective oxytocin antagonist KB-5-21. Calcium mobilization was a likely consequence of enhanced phosphatidylinositol turnover, because oxytocin rapidly increased the formation of inositol phosphates including Ins1,4,5P3. Calcium transients were induced by oxytocin and the oxytocin selective analog AM-2-40 and blocked by the oxytocin-selective antagonist KB-5-21. Lysine vasopressin, the selective V2 agonist dDAVP, and the V1-selective agonist SK&F 105349 were at least 10- to 100-fold less potent than oxytocin and exhibited only partial agonist activity. Using peptide analogs, a poor correlation was found between antagonism of oxytocin-induced calcium transients of LLC-PK1 cells and pig kidney V2 and rat liver V1 receptor affinity. These data indicate that oxytocin-induced calcium transients in LLC-PK1 cells were not mediated by V1 or V2 vasopressin receptors, but by oxytocin receptors. However, the poor correlation between antagonism at the LLC-PK1 receptors and the rat uterus oxytocin receptors suggests marked differences in antagonist recognition. We have also identified specific, saturable, high affinity oxytocin-binding sites of low density on intact LLC-PK1 cells (KD = 1.9 nM; Bmax = 3.2 fmol/10(6) cells). The relative analog affinities for these binding sites correlated well with their effects on oxytocin-induced calcium transients. We conclude that in LLC-PK1 cells, oxytocin stimulates a transient rise in cytosolic free [Ca2+]i and the formation of inositol phosphates, including Ins1,4,5P3. The effects on [Ca2+]i probably are not mediated by V1 and V2 vasopressin receptors, but by putative oxytocin receptors.
Mol Pharmacol 1988 Feb
PMID:Oxytocin induces a transient increase in cytosolic free [Ca2+] in renal tubular epithelial cells: evidence for oxytocin receptors on LLC-PK1 cells. 282 15

Pro-vasopressin mRNA, neurophysin and arginine vasopressin (AVP) were assayed in the mouse anterior pituitary gland, in mouse anterior pituitary cells in culture and in the AtT-20 corticotrophic tumour cell line. Northern blot analysis revealed the presence of an approximately 700 base pair pro-vasopressin mRNA in anterior pituitary and AtT-20 cells. Neurophysin, identified by immunoblots, and AVP, identified by high-performance liquid chromatography and cross-reactivity with AVP antiserum, were detected in anterior pituitary cells and AtT-20 cells. Immunocytochemical staining with anti-neurophysin showed that approximately 40-45% of the dissociated anterior pituitary cells in culture and greater than 95% of the AtT-20 cells were stained. Anterior pituitary cells in culture and AtT-20 cells had a basal level of release of AVP in the 0.01-0.1 nM range. These results indicate that anterior pituitary cells and AtT-20 cells have the ability to synthesize and process pro-vasopressin to AVP and neurophysin, endogenously.
J Mol Endocrinol 1988 Jul
PMID:Presence of pro-vasopressin mRNA, neurophysin and arginine vasopressin in mouse anterior pituitary cells and the AtT-20 corticotrophic tumour cell line. 285 8

Synthesis of the uterine receptor for the hypothalamic hormone oxytocin has been induced in oocytes from Xenopus laevis previously primed with bovine endometrium mRNA. The injected oocytes responded to oxytocin by showing dose-dependent oscillations in membrane currents as recorded by the voltage-clamp method. The response was specific in that it was not elicited by several other peptides tested. The oxytocin-induced membrane changes were suppressed when oocytes were pretreated with an oxytocin receptor antagonist.
J Mol Endocrinol 1988 Jul
PMID:Functional expression of the oxytocin receptor in Xenopus laevis oocytes primed with mRNA from bovine endometrium. 285 10

1. We have reviewed recent studies in which in situ hybridization histochemistry (ISHH) was used to investigate the regulation of expression of neurohypophysial peptides and hypothalamic releasing hormones. 2. ISHH is a technique in which the presence and quantity of a specific mRNA can be determined in tissue sections with a high degree of resolution and sensitivity. 3. ISHH has been used to measure changes in cellular levels of mRNAs encoding vasopressin, oxytocin, corticotropin-releasing factor, gonadotropin-releasing hormone, thyrotropin-releasing hormone and somatostatin in response to various physiological challenges. 4. A theme emerging from these studies is that changes in levels of mRNA encoding neuroendocrine peptides reflect changes in biosynthesis and secretion.
Cell Mol Neurobiol 1987 Dec
PMID:Neuroendocrine gene expression in the hypothalamus: in situ hybridization histochemical studies. 289 79

Sheep corpus luteum homogenates were fractionated by centrifugation on continuous sucrose density gradients, with or without digitonin, and gradient fractions were assayed for progesterone, and for a range of intracellular organelle and plasma-membrane markers. Digitonin had little effect on the density distributions of mitochondrial, rough endoplasmic reticulum (RER) and Golgi-endoplasmic reticulum-lysosomal (GERL) membranes. However, digitonin did disrupt lysosomal membranes, leading to release of acid hydrolases, and induced a decrease in buoyant density of NADH-cytochrome c reductase, a putative smooth endoplasmic reticulum (SER) marker. Oxytocin-containing granules were clearly resolved from other organelles accumulating in a sharp peak (density, 1.20 g/cm3). Luteal cell-surface membrane marker activities equilibrated at similar buoyant densities in control gradients, and pretreatment with digitonin induced a marked increase in their buoyant densities. The majority of the progesterone of the sheep corpus luteum equilibrated at a buoyant density of 1.10 g/cm3 in control gradients, and was highly perturbed by digitonin. These fractions also accumulated [3H]progesterone. The buoyant density profile of progesterone in both control and digitonin-treated gradients most closely resembled that of sheep luteal lactogenic receptor, a putative plasma-membrane marker.
Mol Cell Endocrinol 1988 Sep
PMID:Subcellular fractionation of the ovine corpus luteum: association of progesterone with ovine luteal membranes? 319 18

We have constructed an icosameric, anti-sense oligodeoxyribonucleotide probe derived from the published sequence of rat oxytocin gene precursor that was used for in situ hybridization, combined with immunostaining, to characterize the biosynthetic and secretory activity of hypothalamic oxytocin neurons. The population of hybridized neurons overlapped with the pattern of oxytocin immunoreactive cells, except for a fraction of these cells which remained unhybridized. A number of hybridized neurons remained unstained. The differential proportion of hybridized and immunostained neurons are interpreted as differences in secretory turnover of endocrine neurons.
Mol Cell Probes 1988 Mar
PMID:In situ hybridization with complementary synthetic oligonucleotide and immunocytochemistry: a combination of methods to study transcription and secretion of oxytocin by hypothalamic neurons. 328 65

Experiments were performed with cultured bovine granulosa cells to examine the relationship between the secretions of oxytocin and progesterone and to determine whether progesterone could be responsible for the progressive refractoriness of these cells to stimulation by ascorbic acid. Aminoglutethimide suppressed progesterone secretion by 95% but it neither reduced oxytocin secretion nor restored the cellular response to delayed ascorbate treatment. Addition of a high concentration of progesterone to the culture medium also failed to affect oxytocin secretion, its stimulation by ascorbate, or the endogenous secretion of the steroid. It is concluded that oxytocin and progesterone can be independently secreted and that progesterone regulates neither its own secretion nor that of oxytocin.
Mol Cell Endocrinol 1988 Mar
PMID:Ovarian oxytocin and progesterone are secreted independently of one another. 337 42

Degradation of LHRH and [D-Ser(tBu)6,des-Gly-NH10(2)]LHRH ethylamide (LHRH-A), during incubation with high-speed supernatants of rat testes, as assessed by reversed-phase (RP)-HPLC fractionation of the iodinated peptides and by radioimmunoassays for LHRH or LHRH-A, was principally due to a neutral 43 000 Da peptidase with apparent Km values at 25 degrees C of 0.15 microM for LHRH and 1.19 microM for LHRH-A. The peptidase was inhibited by sulphydryl reagents, TLCK, 1,10-phenanthroline, EDTA, bacitracin, other LHRH analogues, oxytocin, [Lys8]vasopressin and somatostatin. It was predomantly located in seminiferous tubule supernatants (98% of recovered activity), with much lower levels in interstitial fluid (2%), interstitial tissue or testicular particulate fractions (less than 0.8%). Extracts of cultured immature Sertoli cells produced LHRH- and LHRH-A-degradation profiles, as assessed by RP-HPLC, that were identical to those produced by testicular supernatants. Similar levels of peptidase activity/mg protein were observed in immature and adult rat testes. These studies indicate that the principal LHRH-peptidase in the rat testis is produced by cells of the seminiferous epithelium, chiefly the Sertoli cell, and may play an important role in regulating the activity of LHRH and other peptide hormones in the testis.
Mol Cell Endocrinol 1986 Jun
PMID:Degradation of luteinizing hormone-releasing hormone (LHRH) and an LHRH agonist by the rat testis. 351 17

From guinea pig posterior pituitaries, a MSEL-type neurophysin (neurophysin containing methionine-2, serine-3, glutamic acid-6 and leucine-7), a glycopeptide referred to as copeptin and their common precursor have been purified to homogeneity and sequenced. The performed acid-oxidized precursor, subjected to trypsin hydrolysis, has given 9 peptides, 6 of which (T1-T6) identical to those given by oxidized MSEL-neurophysin except that T6 has an additional C-terminal arginine residue when compared to its homologue. The other 3 tryptic peptides (T7-T9) are identical to those given by copeptin. The 132-residue precursor therefore comprises a MSEL-type neurophysin (93 residues) and copeptin (38 residues) linked by an arginine residue. The molar proportion of this bound form compared with the free polypeptides is approximately 20%. It is believed that this precursor is a part of the vasopressin-MSEL-neurophysin-copeptin precursor incompletely processed during the transport from hypothalamus to neurohypophysis.
Mol Cell Endocrinol 1986 Mar
PMID:Structure of a guinea pig common precursor to a MSEL-type neurophysin and copeptin. 395 54


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