Arginine vasopressin inhibits apoptosis of rat glomerular mesangial cells via V1a receptors

Arginine vasopressin (AVP) promotes proliferation of glomerular mesangial cells. We examined whether AVP modulates an apoptosis of cultured rat glomerular mesangial cells at 3-17th passages. The agarose gel electrophoresis demonstrated that AVP attenuated a ladder formation stimulated by the serum deprivation. The quantitation of oligonucleosomes by ELISA also showed that AVP suppressed the serum deprivation-induced apoptosis. Such an antiapoptotic effect of AVP was dose-dependent. An AVP V1a receptor antagonist, d(CH2)5Tyr(Me)AVP, abolished the antiapoptotic effect of AVP. The inhibitory effect of AVP on the apoptosis was reduced by staurosporine and mimicked by phorbol-12-myristate-13-acetate. These results suggest that AVP inhibits serum deprivation-induced apoptosis of glomerular mesangial cells via V1a receptor-protein kinase C pathway.     

Identification and characterization of arginine vasopressin-like substances in the rat testis

We have previously demonstrated the suppression of Leydig cell steroidogenesis by arginine vasopressin (AVP) in vitro. Since the circulating level of AVP is too low to mediate a testicular action of this peptide, we have conducted studies to identify testicular AVP-like substances. The supernatant of homogenized, acid-extracted rat testes was found to contain AVP immunoreactivity which showed parallelism with synthetic AVP in a specific radioimmunoassay for AVP. Chromatography of this extract on a Sephadex G-25 column produced three peaks of AVP immunoreactivity. The largest peak eluted close to the column void volume, a second smaller peak eluted at the total column volume, while a third peak co-eluted with synthetic AVP. Following acetone precipitation, ether extraction, and octadecylsilica (C18) adsorption chromatography of the acid extract, the third peak of AVP immunoreactivity (about 600 pg/testis) was fully retained by C18 chromatography and showed parallelism with synthetic AVP in both radioimmuno- and radioreceptor assays. This substance also co-migrated with synthetic AVP on both Sephadex G-25 and reverse-phase thin layer chromatography (RPTLC). The second peak was only partially retained by C18 adsorption chromatography, dilution curves were not parallel with synthetic AVP in radioimmuno- or radioreceptor assay, and this material failed to co-migrate with synthetic AVP on Sephadex G-25 and RPTLC. The first peak of apparent AVP immunoreactivity was associated with an enzyme(s) that degraded labeled AVP. This enzymatic activity, as well as the immunoreactivity, could be eliminated by heating the extract to 90 degrees C. These results demonstrate, by a number of independent criteria, that rat testes contain a substance which behaves like authentic AVP. Due to its high concentration, the AVP-like peptide may be synthesized or concentrated by testis cells. In addition, testis tissue contains enzymatic activity which degrades AVP and could represent a site of regulation of AVP action. Coupled with the previously demonstrated testis action of AVP, these results suggest a paracrine or autocrine role of the neurohypophysial hormone at the testis level.     

Actin can act as a cofactor for a viral proteinase in the cleavage of the cytoskeleton

Cytoskeletal proteins are exploited by many viruses during infection. We report a novel finding that actin can act as a cofactor for the adenovirus proteinase (AVP) in the degradation of cytoskeletal proteins. Transfection studies in HeLa cells revealed AVP localized with cytokeratin 18, and this was followed by destruction of the cytokeratin network. For AVP to cleave cytokeratin 18, a cellular cofactor was shown to be required, consistent with AVP being synthesized as an inactive proteinase. Actin was considered a cellular cofactor for AVP, because the C terminus of actin is homologous to a viral cofactor for AVP. AVP was shown to bind to the C terminus of actin, and in doing so AVP exhibited full enzymatic activity. In vitro, actin was a cofactor in the cleavage of cytokeratin 18 by AVP. The proteinase alone could not cleave cytokeratin 18, but in the presence of actin, AVP cleaved cytokeratin 18. Indeed, actin itself was shown to be a cofactor and a substrate for its own destruction in that it was cleaved by AVP in vitro. Cleavage of cytoskeletal proteins weakens the structure of the cell, and therefore, actin as a cofactor may play a role in cell lysis and release of nascent virions.     

The cellular actions of vasopressin on corticotrophs of the anterior pituitary: resistance to glucocorticoid action

The cellular actions of vasopressin (AVP) in the anterior pituitary were investigated. HPLC analysis of [3H]inositol-labeled cells indicated that AVP stimulated a rapid increase in inositol-1,4,5 trisphosphate (IP3), inositol-1,4 bisphosphate, and inositol-4 monophosphate levels. While CRF had no effect on basal IP3 levels, it blocked their stimulation by AVP. CRF-stimulated ACTH secretion and cAMP accumulation were potentiated by AVP. AFter dexamethasone (DEX) treatment (20 nM, 18 h), CRF-dependent ACTH secretion and cAMP accumulation were attenuated but AVP was still able to potentiate both of these actions of CRF suggesting that cellular actions of AVP may be resistant to DEX effects. Therefore, [3H]AVP binding was determined in control and DEX-treated cells. Pretreatment with DEX had no effect on either AVP receptor affinity or on the number of available binding sites. Consistently, stimulation of IP3 production by AVP in DEX-treated cells was comparable to that of control cells. Protein kinase C activators such as 12-O-tetradecanoyl-phorbol-13-acetate and dioctanoylglycerol were either near additive with CRF or also potentiated the action of CRF on ACTH secretion, respectively, even after DEX pretreatment. These results indicate that, in the anterior pituitary, distinct intracellular signaling pathways mediate the actions of CRF and AVP; cAMP mediates CRF actions and IP3/protein kinase C mediate the effects of AVP. Neuromodulation of ACTH secretion by dual effector mechanisms which exhibit a complex mode of interaction and only one of which is negatively influenced by glucocorticoids, provides these cells a mechanisms by which appropriate responses can be elicited under various physiological states.     

Analysis of the vasopressin system and water regulation in genetically polydipsic mice

Polydipsic mice, STR/N, which show extreme polydipsia and polyuria, were discovered in 1958. In the STR/N, urine outputs are much higher than in control mice. The possibility of an abnormal regulation of the arginine vasopressin (AVP) system, or an abnormality in the renal susceptibility to AVP, should be considered. In this study we investigated the AVP system and water regulation in STR/N. We sequenced the AVP and the AVP V(2)-receptor genes of the STR/N by direct sequencing. No mutation was found in either of them. AVP gene expression examined by in situ hybridization and plasma sodium in 8-wk-old STR/N was significantly lower than in control mice, whereas it was significantly higher at 20 wk. Renal sensitivity to injected AVP was attenuated in 20-wk-old STR/N. The suppression of AVP synthesis due to excessive water retention in 8-wk-old STR/N suggests that polydipsia may be the primary cause in this strain. The 20-wk-old STR/N became dehydrated with the acceleration of AVP synthesis, which might have resulted from secondary desensitization to AVP.     

Glucose- and concentration-dependence of vasopressin-induced hormone release by mouse pancreatic islets.

The effects of arginine-vasopressin (AVP) on hormone release by the endocrine pancreas have been studied with incubated islets from normal mice. A wide range of AVP concentrations (1 pM-100 nM) were tested in the presence of various glucose concentrations. AVP did not affect somatostatin release in a glucose-free medium but increased it in the presence of all tested glucose concentrations (3-30 mM). The lowest effective concentration was 1 mM and the effect was not yet maximal at 100 nM AVP. AVP markedly increased glucagon release in the absence of glucose. Its effect was attenuated but not abolished when glucagon release was inhibited by glucose. Surprisingly, the attenuation of the effect of AVP was stronger in 3-10 mM than in 15-30 mM glucose. The lowest effective concentration was 1 nM and the effect was not yet maximal at 100 nM AVP. AVP was ineffective on basal insulin release (0, 3 and 7 mM glucose), but potentiated the effect of 10, 15 and 30 mM glucose. The lowest effective concentration was 0.1-1 nM AVP and the maximal effect was produced by 10-100 nM AVP. The results suggest a direct action of AVP on each of the three islet cell types which display a roughly similar sensitivity to the peptide. This sensitivity is too low to make islet cells a possible target for circulating AVP under physiological conditions. On the other hand, the presence of AVP in the pancreas suggests that it might be involved in the peptidergic control of islet function.     

Distension of the pulmonary vein - atrial junctions and plasma vasopressin in the chloralose-anaesthetized dog

The effects of localized distension of the pulmonary vein - left atrial junctions on plasma arginine vasopressin (AVP) have been examined in chloralose anaesthetized dogs. Pulmonary vein distension caused an increase in heart rate and a decrease in plasma AVP concentration. Cooling the vagosympathetic nerves to 10 degrees C caused an increase in arterial pressure and plasma AVP concentration and prevented the changes in heart rate and plasma AVP concentration caused by pulmonary vein distension. Cooling the vagus nerves to 16 degrees C did not change heart rate, arterial pressure, or plasma AVP concentration but significantly reduced the changes in heart rate and plasma AVP concentration caused by pulmonary vein distension. Propranolol (0.5 mg/kg) decreased heart rate and prevented the increase in heart rate associated with pulmonary vein distension but did not abolish the decrease in plasma AVP concentration. It is concluded that distension of the pulmonary vein - left atrial junctions causes a decrease in plasma AVP concentration by stimulating atrial receptors with myelinated afferent fibres. The decrease in plasma AVP concentration is not secondary to the reflex changes in heart rate caused by pulmonary vein distension.     

Effect of intranasal arginine vasopressin on human headache

Arginine vasopressin (AVP), a nonapeptide hormone of posterior pituitary, reaches the central nervous system from systemic blood circulation with a difficulty because of the blood–brain barrier (BBB). The interest has been expressed in the use of the nasal route for delivery of AVP to the brain directly, exploiting the olfactory pathway. Our previous study has demonstrated that AVP in the brain rather than the spinal cord and blood circulation plays an important role in rat pain modulation. For understanding the role of AVP on pain modulation in human, the communication tried to investigate the effect of intranasal AVP on human headache. The results showed that (1) AVP concentration in both plasma and cerebrospinal fluid (CSF) increased significantly in headache patients, who related with the headache level; (2) there was a positive relationship between plasma and CSF AVP concentration in headache patients; and (3) intranasal AVP could relieve the human headache in a dose-dependent manner. The data suggested that intranasal AVP, which was delivered to the brain through olfactory region, could treat human headache and AVP might be a potential drug of pain relief by intranasal administration.     

精氨酸加压素对大鼠抗体产生和淋巴细胞增殖的上调作用

大鼠侧脑室注射１００ｎｇ精氨酸加压素（ＡＶＰ）,用ＥＬＩＳＡ法检测血中对鸡卵白 白抗原产生的ＩｇＧ抗体水平。结果显示,ＩｇＧ水平高于对照,而ＡＶＰ的Ｖ１受体阻断剂ＤＰＡＶＰ则可阻断此作用;ｉｃｖ８００ｎｇＡＶＰ,大鼠的ＳＲＢＣ溶血素 水平高于对照;ｉｃｖ１００ｎｇ、８００ｎｇＡＶＰ２ｈ后,脾淋巴细胞对ＭＴＴ产生的颜色反应均比对照增加,而ＤＰＡＶＰ可阻断之;ｉｃｖ８００ＡＶＰ２ｈ后,脾淋巴细胞对ＭＴ     

Arginine-vasopressin fragment 4-9 stimulates the acetylcholine release in hippocampus of freely-moving rats.

We examined the effects of arginine-vasopressin (AVP) C-terminal fragment 4-9, which facilitates learning and memory, on the extracellular acetylcholine (ACh) release in hippocampus of freely-moving rats using the microdialysis technique. Following administration of AVP4-9, p-Glu-Asn-Cys[Cys]-Pro-Arg-Gly-NH2, through the dialysis probe into the hippocampus, ACh levels in dialysates from the hippocampus increased markedly in dose and time dependent manner at 2-2.5 and 2.5-3 hr. AVP1-9, the parent peptide, has a similar enhancing effect on ACh release as AVP4-9. Stimulated ACh release by AVP4-9 was significantly inhibited by V1-selective receptor antagonist ([1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)-tyrosine]AVP), but not by V2-selective antagonist ([1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-D-Ile, 4-Ile]AVP). From these observations, it is demonstrated that AVP4-9 stimulates the ACh release in rat hippocampus via mediating V1-like vasopressin receptors.     

Intraventricular administration of arginine vasopressin suppresses prolactin release via a dopaminergic mechanism

The present study was conducted to determine the effects of intracerebroventricular administration of arginine vasopressin (AVP) on the preovulatory prolactin (PRL) surge. Hourly injections of 1 or 5 micrograms AVP from 1200 to 1700 hr on proestrus prevented increases in plasma PRL levels that afternoon. However, following cessation of AVP treatment, a marked increase in PRL levels occurred between 1830 and 2030 hr. This "rebound" secretion of PRL was greater in rats given 5 micrograms AVP than in rats given the lower dose. The suppression of PRL release by AVP appears to be mediated by dopamine since 5 micrograms AVP failed to inhibit PRL release in animals pretreated with the dopamine antagonist domperidone. Interestingly, under these conditions, AVP increased PRL release compared to levels observed in saline-treated rats. In addition to suppressing PRL release, AVP exerted a dose-dependent inhibition of preovulatory LH release. The results suggest a possible interaction between AVP and dopamine in controlling PRL release which likely takes place within the median eminence.     

Radioimmunoassay of arginine vasopressin in human plasma.

Antibodies for the radioimmunoassay of arginine vasopressin (AVP) described here were produced in rabbits using synthetic AVP coupled to rabbit gamma-globulin with carbodiimide. In three out of six rabbits, significant antibody titres were obtained. Using the best antisera produced, 40% of labeled AVP was bound at a final dilution of 1:50.000. After iodination of synthetic AVP with 125I using the chloramin-T method, a gel filtration on Sephadex G-25 was performed to purify the iodinated AVP. For separation of antibody bound and free hormone, a second antibody precipitation was used. There was no crossreactivity with oxytocin. AVP was extracted from plasma after ammoniumsulfate precipitation of the proteins by adsorption to Florisil. The recovery of AVP added to plasma in amounts between 5-25 pg/ml was 60 +/- 15% (n equals 6). The minimum amount of AVP detectable was 1 pg per ml plasma. The plasma level in normal adults under standard conditions was 3.4 +/- 2.2 pg/ml. This is in agreement with data recently published by other researchers. The applicability and reproducibility was further tested in measurements of samples taken hourly during the entire day under water diuresis and after hormonal stimulation of AVP.     

Central vasopressin in the modulation of catecholamine release in conscious rats

Neurons containing arginine vasopressin (AVP) have been shown to project from the paraventricular nucleus of the hypothalamus to the nucleus tractus solitarius (NTS) in the medulla. We investigated whether AVP acts in brain stem regions to influence sympathoadrenal outflow. Cannulae were implanted into the fourth ventricle of rats 7 days prior to the experiment. The effects of intracerebroventricular (icv) injections of AVP, the vehicle, and AVP antagonist, d(CH2)5Tyr(Me)AVP, on mean arterial pressure (MAP) and plasma noradrenaline (NA) and adrenaline (A) levels were determined in conscious unrestrained rats. Injections of AVP (icv, 23 and 73 ng/kg) but not the vehicle increased MAP and plasma NA and A levels. In contrast, iv injection of AVP increased MAP but decreased plasma concentrations of A and NA. The pressor response to icv injection of AVP was abolished by prior icv injection of AVP antagonist. Injection of AVP antagonist (icv, 0.5 and 1.5 microgram/kg) had no effect on MAP or plasma NA or A levels. These results show that centrally injected AVP activates sympathoadrenal outflow, possibly via an inhibition of baroreceptor reflexes. Since centrally administered AVP antagonist did not influence MAP or plasma NA or A levels, it appears that endogenously released AVP does not have a tonic influence on central cardiovascular reflex system in conscious, unrestrained rats.     

Organotypic Suprachiasmatic Nuclei Cultures of Adult Voles Reflect Locomotor Behavior: Differences in Number of Vasopressin Cells

This study is the first to demonstrate organotypic culturing of adult suprachiasmatic nuclei (SCN). This approach was used to obtain organotypic SCN cultures from adult vole brain with a previously determined state of behavioral circadian rhythmicity. We examined vasopressin (AVP) immunoreactivity in these organotypic slice cultures. AVP is one of the major neuropeptides produced by the SCN, the main mammalian circadian pacemaker. AVP immunoreactivity in the SCN of adult common voles in vivo has been shown to correlate with the variability in expression of circadian wheel-running behavior. Here, cultures prepared from circadian rhythmic and nonrhythmic voles were processed immunocytochemically for AVP. Whereas in all cultures AVP could be observed, AVP immunoreactivity differed considerably between vole SCN cultures. SCN cultures from rhythmic voles contained significantly lower numbers of AVP immunoreactive (AVPir) cells per surface area than cultures from nonrhythmic voles. The correlation between timing of behavior and AVP immunoreactivity in vitro is similar to the correlation found earlier in vivo. Apparently, such correlation depends on intrinsic AVP regulation mechanisms of SCN tissue, and not on neural or hormonal input from the environment, as present in intact brain.     

Role of arginine vasopressin in control of ACTH and LH release during stress

To determine the role of arginine vasopressin (AVP) in stress-induced release of anterior pituitary hormones, AVP antiserum or normal rabbit serum (NRS) was micro-injected into the 3rd ventricle of freely-moving, ovariectomized (OVX) female rats. A single 3 microliter injection was given, and 24 hours later, the injection was repeated 30 min prior to application of ether stress for 1 min. Although AVP antiserum had no effect on basal plasma ACTH concentrations, the elevation of plasma ACTH induced by ether stress was lowered significantly. Plasma LH tended to increase following ether stress but not significantly so; however, plasma LH following stress was significantly lower in the AVP antiserum-treated group than in the group pre-treated with NRS. Ether stress lowered plasma growth hormone (GH) levels and this lowering was slightly but significantly antagonized by AVP antiserum. Ether stress also elevated plasma prolactin (Prl) levels but these changes were not significantly modified by the antiserum. To evaluate any direct action of AVP on pituitary hormone secretion, the peptide was incubated with dispersed anterior pituitary cells for 2 hours. A dose-related release of ACTH occurred in doses ranging from 10 ng (10 p mole)-10 micrograms/tube, but there was no effect of AVP on release of LH. The release of other anterior pituitary hormones was also not affected except for a significant stimulation of TSH release at a high dose of AVP. The results indicate that AVP is involved in induction of ACTH and LH release during stress. The inhibitory action of the AVP antiserum on ACTH release may be mediated intrahypothalamically by blocking the stimulatory action of AVP on corticotropin-releasing factor (CRF) neurons and/or also in part by direct blockade of the stimulatory action of vasopressin on the pituitary. The effects of vasopressin on LH release are presumably brought about by blockade of a stimulatory action of AVP on the LHRH neuronal terminals.     

Angiotensin II-stimulated secretion of arginine vasopressin is inhibited by atrial natriuretic peptide in humans

We investigated the effect of the intravenous infusion of atrial natriuretic peptide (ANP) on the response of plasma arginine vasopressin (AVP) levels to intravenous infusion of angiotensin II (ANG II) in healthy individuals. Intravenous infusion of ANP (10 ng·kg(-1)·min(-1)) slightly but significantly decreased plasma AVP levels, while intravenous infusion of ANG II (10 ng·kg(-1)·min(-1)) resulted in slightly increased plasma AVP levels. ANG II infused significant elevations in arterial blood pressure and central venous pressure (CVP). Because the elevation in blood pressure could have potentially inhibited AVP secretion via baroreceptor reflexes, the effect of ANG II on blood pressure was attenuated by the simultaneous infusion of nitroprusside. ANG II alone produced a remarkable increase in plasma AVP levels when infused with nitroprusside, whereas the simultaneous ANP intravenous infusion (10 ng·kg(-1)·min(-1)) abolished the increase in plasma AVP levels induced by ANG II when blood pressure elevation was attenuated by nitroprusside. Thus, ANG II increased AVP secretion and ANP inhibited not only basal AVP secretion but also ANG II-stimulated AVP secretion in humans. These findings support the hypothesis that circulating ANP modulates AVP secretion, in part, by antagonizing the action of circulating ANG II.     

Vasopressin gene expression in the normal and Brattleboro rat: a histological analysis in semi-thin sections with biotinylated oligonucleotide probes

We analyzed expression of the vasopressin (AVP) gene in semi-thin sections in normal and Brattleboro rats by using in situ hybridization and immunohistochemistry. AVP mRNA was detected as follows: vibratome sections of rat hypothalamus were hybridized with a biotinylated oligonucleotide probe, embedded in Araldite, and cut into semi-thin sections which were reacted with streptavidin-alkaline phosphatase and the appropriate substrate. Adjacent serial sections were treated by immunohistochemistry to detect AVP or oxytocin immunoreactivity. In normal rat, AVP mRNA can be detected in magnocellular neurons of the supraoptic and paraventricular nuclei and in parvocellular neurons of the suprachiasmatic nucleus. AVP mRNA was present throughout the cytoplasm of the cell bodies, their processes, and in punctate structures in the vicinity of the AVP cell bodies. Most neurons containing AVP mRNA also contain AVP immunoreactivity, but the staining intensity was not consistently correlated for each reaction. A few neurons contained AVP mRNA without detectable AVP immunoreactivity. In the Brattleboro rat, staining intensity of the reaction was lower than in normal rat and the AVP mRNA was restricted mostly to the periphery of the cytoplasm. In this strain, the neurons containing the AVP mRNA did not contain AVP or oxytocin immunoreactivity. These results demonstrate that neuropeptide mRNA can be detected in semi-thin sections with a biotinylated oligonucleotide probe, and that AVP gene deletion provokes modification of the intracellular localization of the AVP mRNA.