Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The neurohypophysial osmoregulatory hormones of the African toad Bufo regularis, a species adapted to estivate under dry and hot conditions, have been investigated. Vasotocin and hydrin 2 (vasotocinyl-Gly) have been identified by their retention times in high-pressure reverse-phase liquid chromatography and coelution with synthetic peptides, their pharmacological properties (vasotocin) and microsequencing. 2. Vasotocin-associated neurophysin (MSEL-neurophysin type) has been characterized by its N-terminal amino acid sequence. 3. In toads subjected to dehydration by evaporation (20% weight loss) or to osmotic stress by immersion in 2% NaCl for 3 hr (6% weight loss), the molar ratio hydrin 2/vasotocin (about 2:1) remained similar to the one observed in control animals. 4. In toads exposed to saline solution, there was a large decrease (roughly 30%) in the amounts of both hormones in the neuro-hypophysis. Environmental conditions for distinct secretions of vasotocin and hydrin 2 remain to be found.
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PMID:Vasotocin and hydrin 2 (vasotocinyl-Gly) in the African toad Bufo regularis: study under various environmental conditions. 809 51

Secretion of the antidiuretic hormone (ADH) vasopressin is increased when body fluid homeostasis is disturbed by dehydration. Associated with this increased secretion is an elevation of vasopressin mRNA in magnocellular hypothalamic neurons projecting to the posterior pituitary. The proto-oncogene c-fos codes for a nuclear phospho-protein Fos which binds to specific DNA elements and acts as a transcriptional regulator coupling short-term extracellular stimuli to long-term responses by altering secondary target gene expression. This study in rats examined the time courses of dehydration induced c-fos expression and the change of vasopressin gene expression in the magnocellular neurons of the hypothalamus. Immunocytochemical and in situ hybridization study demonstrated that c-fos was induced by acute intracellular dehydration in the hypothalamic magnocellular nuclei of paraventricular (PVN), supraoptic (SON), and accessory groups such as nucleus circularis. Double-label immunocytochemical study co-localized Fos and vasopressin-neurophysin immunoreactivity in the same magnocellular neurons in the SON and PVN. In situ hybridization analysis after acute dehydration revealed a rapid and transient c-fos induction followed by a persistent increase in vasopressin mRNA for up to 2 days even after rehydration. Furthermore, prevention of c-fos translation by pretreatment with protein synthesis inhibitor cycloheximide attenuated this dehydration induced increase in vasopressin mRNA. This study demonstrated that an increase in vasopressin transcription after acute dehydration is dependent on an early phase of protein synthesis.
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PMID:Proto-oncogene c-fos and the regulation of vasopressin gene expression during dehydration. 817 Mar 49

Magnocellular neuroendocrine cells (MNCs) in the supraoptic nucleus (SON) of the hypothalamus have been known to undergo dramatic structural changes during chronic stimulation such as osmotic stress. In the present study, we examined whether this anatomical neural plasticity is associated with an another stress, such as restraint. Rats were chronically stimulated by either dehydration with 2% saline drinking instead of water or daily restraint with leg immobilization. The structural reorganizations of MNCs in the SON were analyzed morphometrically with use of light and electron microscopy. The results were compared to control animals that had free access to water and food. In restraint rats, the soma size of both oxytocin (OXT) and arginine vasopressin (AVP) neurons was enlarged, and the percent of soma-somatic/dendritic membrane contact (juxtaposition) was elevated significantly. The number of total synapses per 100 microns soma membrane was not changed, although soma profiles were enlarged. However, the number of multiple synapses (which contacted with more than one postsynaptic element) per 100 microns soma membrane was significantly increased. Similar structural changes were observed in dehydrated animals, and the degree of morphological changes was stronger than the restraint one. These findings indicate that NMCs undergo structural plasticity during not only osmotic stress but also restraint stress.
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PMID:Not only osmotic stress but also repeated restraint stress causes structural plasticity in the supraoptic nucleus of the rat hypothalamus. 819 21

Peptide contents of neural lobes from adult jerboas (Jaculus orientalis) under different states of hydration were determined by radioimmunoassay. The amounts of vasopressin, oxytocin, and their associated neurophysins in animals dehydrated for up to 4 weeks were not significantly different from those of controls. The different neurohypophyseal peptide were separated on two different types of gradient using reverse-phase high-performance liquid chromatography. The shape of the chromatograms suggests that, in contrast to the case of the rat, for which only three types of neurophysins have been shown, there are, in jerboa, many subspecies of neurophysins. This was also shown using two-dimensional electrophoresis. Injection of [35S]cysteine into the supraoptic nucleus followed by HPLC of extracts from the neural lobes from animals under different states of dehydration showed that the labeled material is not released any faster in dehydrated animals than in controls. Labeled vasopressin, oxytocin, and neurophysins could still be detected by HPLC 4 weeks after injection. Neural lobes from animals injected with [35S]cysteine were perfused in vitro and the release of neuropeptides was triggered by bursts of electrical pulses and also by K(+)-induced depolarization. The amplitude of the rate constant for release and the amounts of vasopressin and of radiolabeled material released were similar in animals dehydrated for up to 3 weeks and in controls. Under physiological conditions similar to those that would be expected to occur in their natural habitat, the jerboas appear to have a hypothalamoneurohypophyseal system which is down-regulated.
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PMID:Synthesis, turnover, and release of peptides from the neurohypophysis of the Jerboa Jaculus orientalis. 819 37

Ethanol ingestion affects the hypothalamo-neurohypophysial system resulting in increased diuresis, dehydration and hyperosmolality. We studied the supraoptic nucleus, of the hypothalamus, in ethanol-treated rats, to determine if ethanol alone and/or the associated disturbances of water metabolism lead to structural alterations in a nucleus known to play a central role in fluid homeostasis. Groups of male and female rats were ethanol-treated until 12 and 18 months of age and compared with age-matched pair-fed controls. Twelve and 18-month-old control groups and 12-month-old water control groups (rats submitted to chronic dehydration) were also included in this study in an attempt to differentiate between the effects of undernutrition and dehydration/hyperosmolality, and the specific neurotoxic effects of ethanol. We estimated the volume of the supraoptic nucleus and the numerical density of its neurons and calculated the total number of supraoptic neurons. The volume of both supraoptic neurons and neuropil were also estimated. In immunostained material the ratio of vasopressin to oxytocin neurons and the cross-sectional areas of the two neuronal types were evaluated. There was marked neuronal loss in alcohol-treated rats, but the volume of the supraoptic nucleus was increased. The increase in the volume of the supraoptic nucleus correlated with and was due to increases in the volume was particularly marked for vasopressin neurons. No significant differences were found between controls and pair-fed controls in any of the parameters investigated. In water control rats, the volume of the supraoptic nucleus and of the supraoptic neurons and neuropil was also greater than in pair-fed controls. However, the variations found were not as marked as in ethanol-treated rats and there was no cell loss. These findings reveal, for the first time, that chronic ethanol consumption affects the morphology of supraoptic neurons and neuropil and, consequently, the structure of the entire supraoptic nucleus. Moreover, this study supports the view that ethanol has direct neurotoxic effects on supraoptic neurons because the alterations that occur are not mimicked in animals in which water metabolism alone is disturbed.
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PMID:Effects of chronic alcohol consumption and of dehydration on the supraoptic nucleus of adult male and female rats. 825 26

A study was performed investigating the daily patterns of hormone release accompanying changes in fluid balance in the male rat during 48 h of dehydration. The blood volume decreased by 18%, the largest change occurring during the initial period when the rats showed an effective loss of body sodium. During the second day of dehydration, sodium retention was again seen. Plasma sodium concentrations showed a progressive increase, the total rise being 5-6%; the greatest changes were seen during the dark phases of the cycle which may be due to the nocturnal food intake. Plasma vasopressin and oxytocin concentrations were significantly elevated throughout dehydration to levels which could be reproduced by acutely increasing plasma sodium and decreasing blood volume to the same extent. The observed increases were influenced by the phase of the day-night cycle, being greatest over the dark phases of the cycle. The overall increases were greatest when dehydration commenced at the start of the dark phase. Dehydration initially led to a rise in plasma corticosterone concentrations, whilst plasma concentrations of atrial natriuretic peptide were decreased. Plasma angiotensin II concentrations rose significantly during the later period of sodium retention.
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PMID:Patterns of neurohypophysial hormone release during dehydration in the rat. 832 57

Transcription of cell-specific vasopressin and oxytocin genes as well as transcription of those housekeeping genes responsible for general metabolic activation and cellular hypertrophy is induced in supraoptic hypothalamic neurons by rises in plasma osmolarity. In this study, the nuclear volume, the ultrastructure of chromatin and the number and distribution of nuclear particles in the cell nuclei of supraoptic neurons of 3-month-old male Sprague-Dawley rats were analyzed after osmotically induced activation of transcription by periods of acute (1 day) and chronic (6 days) dehydration, and after halting the stimulation by rehydration of animals. The nuclear volume and the ultrastructure of chromatin were assessed on ultrathin sections. The number and distribution of nuclear particles were assessed on freeze-fracture replicas. The initial phase of osmotically induced enhancement of transcription was accompanied by an increase in nuclear volume and by a partial replacement of nuclear particles of large diameter (> 11 nm) by smaller nuclear particles. This latter change affected predominantly the nuclear periphery (0-1,000 nm from the nuclear membrane) and occurred simultaneously with a partial decondensation of chromatin clusters that may be related to chromatin unfolding. In chronically stimulated animals, the decondensation of chromatin and the replacement of large nuclear particles by smaller ones was enhanced in the nuclear periphery and was partially propagated to the interior of the nucleus. After suppression of cellular activation by rehydration of animals, the number of nuclear particles returned to control levels in the nuclear periphery while in the center of the nucleus the number of small particles decreased and the number of large particles increased as compared to control values. These results, together with the observation that in unstimulated cells the nuclear periphery and the nuclear interior differ in their composition of nuclear particles, evidence a structural and functional compartmentalization in the cell nucleus of supraoptic neurons.
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PMID:Nuclear compartmentalization in transcriptionally activated hypothalamic neurons. 836 93

Male rats were deprived of water for 5 days, and then given water ad libitum for 3, 7, 10 or 14 days. Plasma osmolarity returned to normal in less than 3 days, while pituitary vasopressin (AVP) and oxytocin (OXT) only returned to control levels after 14 days. Sections of the supraoptic nucleus (SON) were hybridized with 35S-labelled cDNA (OXT) or oligonucleotide (AVP) probes. Relative AVP and OXT mRNA contents were quantitated by counting the number of silver grains on a large standard area of the SON, then extrapolating this value to the volume of the whole SON (deduced from surface areas of all the sections). Dehydration significantly enlarged the volume of the SON (x 1.54) and increased the AVP and OXT mRNAcontent (x 2). During rehydration, both SON volume and density of silver grains were higher than normal for at least 7-10 days, although levels started to fall by day 3. The distribution of individual cells according to their silver grain densities remained unimodal during the dehydration-rehydration sequence with an extension, then a return to normal of the distribution range. Maximum sizes of AVP and OXT mRNAs on Northern blots of RNAs extracted from 5 pooled SONs were observed on dehydration day 5. The size of these species fell progressively, reaching control values by rehydration day 14. We conclude that during rehydration, at a time when most of the putative inducers of gene transcription are no longer activated, the peptidergic deficit was accompanied by an increased level of AVP and OXT mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Alterations in vasopressin and oxytocin messenger RNA in the rat supraoptic nucleus during dehydration-rehydration evaluated by in situ hybridization and northern blotting. 847 92

The adult oxytocinergic system undergoes extensive synaptic and neuronal-glial remodelling in response to differing conditions of secretion and has become a remarkable example of activity-dependent structural plasticity in the adult mammalian brain. Under stimulation (parturition, lactation, chronic dehydration), glial coverage of oxytocin neurons is significantly reduced and their surfaces become extensively juxtaposed; concurrently, they are contacted by an increased number of synapses. These changes are reversible with cessation of stimulation. We here present observations showing that putative inhibitory and excitatory afferents contribute to this synaptic plasticity. The data are derived from several different comparative analyses of ultrathin sections of the rat supraoptic nucleus (SON) in which presynaptic (gamma-amino butyric acid (GABA) or glutamate) and postsynaptic (oxytocin or vasopressin) partners were identified with postembedding immunogold staining. We thus found that in virgin rats, under basal conditions of oxytocin release, 30-40% of synapses on oxytocinergic or vasopressinergic somata in the SON are GABAergic and about 20% glutamatergic. On the other hand, in lactating rats, in which oxytocin secretion is greatly enhanced, there was an increase in the incidence of both types of synapses, and in particular, on those impinging on oxytocinergic somata.
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PMID:Physiologically-linked structural plasticity of inhibitory and excitatory synaptic inputs to oxytocin neurons. 871 61

In a previous study in rats we demonstrated the existence of osmoregulatory natriuretic mechanisms distinct from the natriuretic mechanisms that are dependent on volume stimulation. At the same time, we found that oxytocin (OT) receptors were important mediators of natriuresis induced by hypernatremia but not of that induced by isotonic volume expansion. In the present study, the role of OT in dehydration natriuresis was examined in conscious rats. Dehydration for 24 h caused hypernatremia (from 142.1 +/- 0.4 to 147.7 +/- 0.7 mmol/l) and natriuresis accompanied by an approximately 30% spontaneous reduction of food intake. In conjunction with renal retention of water caused by an increase in circulating vasopressin, the natriuresis and probably the reduction of food intake can help to counteract the rise in body fluid osmolality. This natriuresis could not be fully explained by the reduction in plasma aldosterone. Plasma OT concentration had increased from 15.5 +/- 1.2 to 23.8 +/- 2.0 pg/ml at the end of 24 h of dehydration. Intravenous infusion of a selective OT-receptor antagonist [Mpa1,D-Tyr(Et)2, Thr4, Orn8]-OT using osmotic minipumps prevented dehydration natriuresis. It is concluded that in a dehydration-induced hypernatremic state OT is released, inducing natriuresis and facilitating sodium homeostasis. This mechanism is activated by Na osmoreceptors, but is not primarily dependent on the volume status.
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PMID:Dehydration natriuresis in male rats is mediated by oxytocin. 877 75


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