Immunoreactive Arginine Vasopressin Research Articles

Androgen manipulation and vasopressin binding in the rat brain and peripheral organs.

It is now widely recognized that there is a sexual dimorphism in the development of arginine vasopressin (AVP) immunoreactivity in certain parts of the brain, and that changes in brain AVP immunoreactivity change with manipulation of androgen status. The aim of this experiment was to determine specifically any AVP receptor changes in response to manipulation of androgen levels using a selective V1 antagonist radioligand. Following castration, plasma testosterone levels fell and AVP immunoreactivity was reduced in the lateral septum and bed nucleus of the stria terminalis. With testosterone supplementation in castrated animals, the immunoreactivity in these regions was restored to a higher degree than in sham-operated animals. Central and peripheral V1 AVP receptor binding (as determined using the selective AVP V1 antagonist radioligand [125I](d(CH2)5,sarcosine7)AVP was not changed in any of the brain regions studied or in liver or kidney membranes from the three groups. This study demonstrates that there is no change in brain AVP receptor binding despite changes in regional AVP immunoreactivity in the brain, and excludes any confounding interaction with changes in oxytocin receptors.

Testosterone effects on paternal behavior and vasopressin immunoreactive projections in prairie voles ( Microtus ochrogaster)

Castration reduced paternal responsiveness of male prairie voles ( Microtus ochrogaster). Castration also reduced the number of vasopressin immunoreactive (AVP-ir) cells in the bed nucleus of the stria terminalis (BST) and medial amygdaloid nucleus (MA), as well as the density of AVP-ir fibers in the lateral septum. Testosterone treatment of castrated voles prevented these changes. The similarities in the effects of the hormonal manipulations on paternal responsiveness and AVP immunoreactivity provide further support for the hypothesis that AVP-ir projections of the BST and MA are implicated in paternal behavior.

Effect and Content of Arginine Vasopressin in Normal and Obstructed Rat Urinary Bladder: An in Vivo and in Vitro Investigation

The present investigation was performed to evaluate the possible role of arginine vasopressin (AVP) in detrusor instability in the obstructed rat urinary bladder. The effect of AVP on normal and obstructed rat detrusor smooth muscle was tested in vivo and in vitro. Arginine vasopressin given as a closed intraarterial injection to the bladder transiently decreased micturition volume and increased micturition frequency during cystometry in control rats. In rats with infravesical outlet obstruction the effect of AVP on cystometrical parameters was negligible. In accordance with this finding, the efficacy of AVP in contracting detrusor muscle in vitro was much lower for obstructed bladders than for controls. The EC50 values were, however, similar. Arginine vasopressin added to the bath had no effect on nerve-mediated contractile responses. Obstruction led to a transient decrease in immunoreactive AVP concentration, but the total amount of AVP per bladder increased significantly after 6 weeks of obstruction as a consequence of the 14-fold increase in bladder weight. The decreased excitatory effect of AVP in obstructed bladder makes a role for this peptide in the development of detrusor instability less likely.

Estradiol increases the behavioral response to arginine vasopressin (AVP) in the medial preoptic-anterior hypothalamus

Flank marking, a form of hamster scent marking controlled by arginine vasopressin (AVP) in the medial preoptic-anterior hypothalamus (MPOA-AH), is altered by circulating levels of gonadal hormones. We hypothesized that gonadal hormones influence flank marking either by altering the availability of AVP for release in the MPOA-AH or by altering the sensitivity or responsiveness of MPOA-AH neurons to AVP. We examined the levels of AVP immunoreactivity (AVP-IR) over the estrous cycle in the MPOA-AH and other areas. Arginine vasopressin immunoreactivity did not vary in the areas examined as a function of the stage of the estrous cycle. In Experiment 2 we measured flank marking after MPOA-AH microinjection of AVP in ovariectomized hamsters receiving estradiol or empty Silastic capsules. Hamsters implanted with estradiol capsules marked significantly more in response to AVP than did hamsters receiving no hormone replacement. These results support the hypothesis that estradiol influences flank marking by altering the sensitivity or responsiveness of the MPOA-AH or its efferents to AVP. Additionally, we observed an unexpected effect of AVP in estradiol-treated hamsters. After microinjection with 90 μ M AVP, lordosis occurred spontaneously in 60% of the hamsters even though no male was present. We suggest that female hamsters may be a useful model to further investigate the role of AVP and AVP-like peptides in female sexual behavior.

The Sites and Consequences of Melatonin Binding in Mammals

SYNOPSIS. Melatonin, a hormone of the pineal gland, exerts multiple effects upon the brain-pituitary axis of vertebrates. Among mammals, the best documented physiological roles of melatonin involve the photoperiodic induction of reproductive and other seasonal adjustments. Daylength regulates the effects of gonadal steroids upon gonadotropin secretion and sexual behavior as well as the frequency of a neural generator of GnRH pulses. In hamsters, these effects are paralleled by changes in GnRH, AVP and beta-endorphin immunoreactivity, and in opiate receptor density in the medial amygdala. Autoradiographic studies indicate a high concentration of 2[125I]-iodomelatonin binding sites in the suprachiasmatic nuclei of some photoperiodic mammals but not in others. In contrast, such binding sites have been found in the pars tuberalis of all seasonally breeding mammals studied to date.

Testosterone Induces an All-or-None, Exponential Increase in Arginine Vasopressin mRNA in the Bed Nucleus of Stria Terminalis of the Hypogonadal Mouse

The bed nucleus of the stria terminalis (BNST) in rodents contains arginine vasopressin (AVP) neurons which project to the lateral septum (LS) and habenula (LH) and are thought to be important for social recognition or memory. In previous studies we demonstrated that AVP immunoreactivity in the LS and LH is absent in the hypogonadal ( hpg) mouse and that AVP immunoreactivity in the LH and LS of this mutant can be induced by testosterone. The aim of the present study was to determine whether this action of testosterone was due to the induction of AVP gene expression in BNST neurons and if so the time taken for testosterone to exert its effect. We found that exposure to supraphysiological concentrations of testosterone for 6-12 days caused an exponential, 50-fold increase in the number of cells that expressed AVP mRNA in the BNST in hpg mice. The action of testosterone is "all-or-none" in that the level of AVP mRNA in the AVP-positive cells was similar at all times after testosterone implantation and also similar or less than that in the few AVP-positive cells in animals not treated with testosterone. The relatively long time taken for testosterone to exert its effect on AVP mRNA in BNST neurons is comparable to its effects on AVP immunoreactivity in the LH and LS and on behaviour and suggests that the action of testosterone may be mediated by indirect or slow intracellular transduction mechanisms.

Urinary excretion of angiotensin I, II, arginine vasopressin and oxytocin in patients with anaphylactoid reactions.

Human urine samples, purified on octadecasilyl-silica cartridges, contained immunoreactive angiotensin I, II, arginine vasopressin and oxytocin. The daily excretion of these peptides in healthy volunteers was 190.00 +/- 38.43 (n = 12), 17.48 +/- 3.09 (n = 12), 63.43 +/- 14.84 (n = 8) and 13.52 +/- 1.42 (n = 7) pmol/24 hr, respectively (mean +/- s.e.m.). Patients with a history of anaphylactoid reactions to drugs or food additives showed clinical symptoms such as urticaria, flush, nausea, dizziness and hypotension after oral provocation with cyanocobalamine, propyphenazone, acetylsalicylic acid and sodium benzoate. In five of the seven patients, angiotensin I and II were increased several fold in the urine fractions after symptoms were reported. The average increase in the urine concentration of both peptides was fourfold and 5.5-fold. In three out of five patients, the mean excretion of arginine vasopressin and oxytocin immunoreactive material was also elevated by a factor of 5.7 and 4.4, respectively. Oral provocation with a placebo failed to elicit anaphylactoid symptoms or an increase in the urine levels of angiotensin I or angiotensin II. Angiotensin I and angiotensin II-like immunoreactivity could be characterized on HPLC as Ile5-angiotensin I, Ile5-angiotensin II and angiotensin II metabolites. HPLC characterization of immunoreactive arginine vasopressin and oxytocin in two different gradient systems showed retention times different than the retention times of the corresponding synthetic standard peptides indicating that both peptides are not authentic AVP and OXT. These results suggest that angiotensin I and angiotensin II may be involved in the clinical events observed during some forms of anaphylactoid reactions.

Contractile effect and tissue content of arginine vasopressin in the urinary bladder of Brattleboro rats with hereditary diabetes insipidus

1. 1. Urinary bladders from male rats of the Brattleboro strain with hereditary diabetes insipidus (DI) were analyzed for presence of immunoreactive arginine vasopressin (ir-AVP). Healthy rats were used as controls. 2. 2. Bladders from the DI rats were heavier than controls. Concentration of ir-AVP was lower in DI bladders, but total amount of ir-AVP was similar to that in controls. 3. 3. EC 50 values for the AVP concentration-response relations were similar for control and DI bladder strips. Maximum response to AVP relative to response to K + high solution was lower in the DI group. 4. 4. An AVP receptor antagonist that significantly blocked response to exogenous AVP had no effect on response to field stimulation. 5. 5. We suggest that AVP is synthetized locally and that AVP is not the non-adrenergic non-cholinergic transmitter responsible for the atropine resistant contraction in rat bladder.

Characterization of a vasopressin-like peptide in rat and bovine blood vessels.

The present study examined the possibility that blood vessels of the rat and cow contain arginine vasopressin (AVP) and that the vascular stores of this potent vasoconstrictor are of local, rather than blood-borne, origin. Vessels from rat or cow were homogenized in acid, and the supernatants were assayed for AVP by radioimmunoassay. AVP immunoreactivity was detected in all vessels taken from the rat including aorta, mesenteric artery, renal artery, vena cava, and renal vein, as well as atria of the heart and also in cow aorta. Blood vessels from hypophysectomized and Brattleboro rats also contained AVP at levels similar to those of intact control rats. Further characterization of this immunoreactive material showed that, in both radioimmunoassay and radioreceptor assay, vascular extracts produced competition curves, which were parallel to those of synthetic AVP. Additionally, immunoreactive AVP in aortic extracts comigrated with synthetic AVP and pituitary extract on both high-pressure liquid chromatography and Sephadex G-25 chromatography. Furthermore, intravenous administration of the aortic extract produced pressor responses in conscious rats, and these responses were significantly attenuated by pretreatment with a specific AVP V1-receptor antagonist. These data demonstrate that blood vessels contain an AVP-like peptide that appears indistinguishable from authentic AVP and further suggest that this vascular peptide is of local origin.

Plasma immunoreactive atrial natriuretic peptide and vasopressin after ethanol intake in man.

To study the mechanisms of alcohol-induced diuresis, the plasma concentration of immunoreactive atrial natriuretic peptide and arginine vasopressin, serum sodium and osmolality, plasma renin activity and aldosterone, urinary sodium and volume, free water clearance, blood pressure and heart rate were measured in seven healthy men after oral intake of ethanol (1.5 g kg-1 in 6 h). Serum ethanol levels increased to 27 +/- 4 mmol l-1 (mean +/- SD) in 30 min and remained detectable for 14 h. Serum osmolality rose from 280 +/- 10 to 340 +/- 4 mosm kg-1 in 2 hours (P less than 0.01) and was 300 +/- 4 at 14 h (P less than 0.01). Formation of hypotonic urine began after the alcohol intake and resulted in a net loss of 0.9 +/- 0.1 kg water in 2 h. Free water clearance increased from -3.4 +/- 1.4 to 2.8 +/- 1.5 ml min-1 in 2 h (P less than 0.01). Plasma immunoreactive arginine vasopressin decreased from 5.7 +/- 2.1 to 3.3 +/- 1.3 ng l-1 (P = 0.05) in 30 min and increased to 17 +/- 25 and 12 +/- 10 ng l-1 at 6 and 12 h, respectively (P less than 0.05 for both). Plasma immunoreactive atrial natriuretic peptide levels decreased from 17 +/- 9 to the minimum of 11 +/- 3 ng l-1 in 2 h (P less than 0.01) and returned to the initial levels in 6 h. Serum sodium, plasma renin activity and plasma aldosterone increased maximally by 4 +/- 2, 165 +/- 153 and 143 +/- 101% (P less than 0.01 each) during 1-6 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic peptide during water deprivation or hemorrhage in rats. Relationship with arginine vasopressin and osmolarity

The concentrations of atrial natriuretic peptide (ANP) in atria, hypothalami and plasma were investigated in relation to the variations of the plasma endogenous immunoreactive arginine vasopressin (Ir-AVP) during water deprivation or hemorrhage in normal conscious Wistar rats. Furthermore, the in vitro and in vivo effect of extracellular hyperosmolarity on ANP release from right atrium and hypothalamus was examined. Water deprivation elevated circulating immunoreactive ANP (Ir-ANP : pg/ml) to 153 ± 7 (24 h); 174 ± 1 (48 h) from the control level (109.6 ± 7.8). This increase in Ir-ANP concentration which correlated with atrial ( r = −0.93) or hypothalamic ( r = −0.87) Ir-ANP content decrease, was associated with significantly enhanced levels of plasma Ir-AVP, plasma sodium, osmolarity and hematocrit. An acute volume depletion by hemorrhage significantly reduced plasma Ir-ANP (67 ± 8.4 pg/ml). Plasma Ir-AVP was elevated dramatically (207.4 ± 53.4 pg/ml) compared with the sham operated level (8.8 ± 2.6 pg/ml). These results, indicating the lack of correlation between plasma Ir-ANP and Ir-AVP in vivo, suggest that the ANP secretion, which is regulated mainly by plasma volume, may be modulated by a change in plasma osmolarity. Extracellular hyperosmolarity stimulated the ANP release from superfused sliced normal rat atria and hypothalami.

Effect of V2 antagonist on clearance of arginine vasopressin by isolated perfused rat kidneys

Isolated rat kidneys were perfused with Krebs-Henseleit-bovine serum albumin solution at a mean pressure of 99 +/- 2.6 mmHg. After control periods, arginine vasopressin (AVP) was added to the perfusate at a final calculated concentration of 25 pg/ml (2.5 x 10(-11) M). Urine and perfusate samples were collected at 15-min intervals for the following 60 min to measure kidney function and the renal clearance of immunoreactive AVP (irAVP). At 15-30 min after the addition of AVP, total renal clearance of irAVP was 1,623 +/- 190 microliters.min-1.g kidney wt-1. Glomerular filtration accounted for 35 +/- 3.0% of the total clearance, and 65 +/- 10.3% was cleared by peritubular pathways. Of the filtered irAVP, 48 +/- 4.8% was recovered in the urine. To investigate the importance of V2 receptors in the metabolism of AVP, clearance measurements were made in the presence of the V2 antagonist [d(CH2)5,D-Ile2,Ile4,Arg8]AVP (5 x 10(-9) M). Total renal clearance of irAVP was reduced by 48% to 848 +/- 79 microliters.min-1.g-1. This reduction was entirely accounted for by the complete inhibition of peritubular clearance of irAVP. In the presence of the V2 antagonist, irAVP was cleared only by filtration. The proportion of filtered AVP recovered in the urine (53 +/- 8.7%) was not significantly altered by the presence of the V2 antagonist. We conclude that a major component of the renal clearance of AVP depends on receptor-mediated uptake of AVP in the kidney cells.

Novel Vasopressin Gene-Related Transcripts in Rat Testis

Although the arginine vasopressin (AVP) gene is predominantly expressed in specific hypothalamic neurons, immunoreactive AVP (irAVP) has also been identified in peripheral tissues, including testis. To determine whether hypothalamic and testicular ir-AVPs derive from the same or different transcripts, we examined testicular AVP gene-related transcripts by Northern blot analysis, polymerase chain reaction (PCR), and RNase mapping. We show that the testis contains three distinct AVP gene-related transcripts of 0.67, 0.83, and 2.0 kilobases (kb) which differ in size from the 0.81-kb hypothalamic AVP mRNA. As demonstrated by deadenylation, this size heterogeneity is not due to differences in the length of the poly(A) tails. By the use of exon-specific probes we determined that the 0.67- and the 0.83-kb transcripts contain exons B and C, but not A. In contrast, the 2-kb transcript is the only testicular transcript that contains an exon A-related sequence. By application of the PCR technique, we confirm the existence of testicular transcripts in which exons B and C are spliced together, but exon A is excluded. Our findings indicate that the 0.67- and 0.83-kb mRNA results from a differential splicing event that excludes exon A and that the 2-kb mRNA probably originates from the expression of an AVP-related gene. Since the nonapeptide AVP is encoded by exon A, testicular irAVP cannot arise from the translation of any of the exon B- and C-containing transcripts, and any mRNA that has so far been identified by AVP exon C probes is unrelated to the biosynthesis of AVP-immunoreactive products.(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine-vasopressin immunoreactivity is not altered by photoperiod or gonadal hormones in the Syrian hamster ( Mesocricetus auratus)

The present study examined whether gonadal hormones or photoperiodic control influence arginine-vasopressin (AVP) immunoreactivity in the Syrian hamster ( Mesocricetus auratus) as has been reported in several other rodent species. Male hamsters were castrated or sham-castrated and exposed to LD 14/10 or LD 6/18 for 13 weeks. Photoperiod and castration significantly altered body weight and the levels of circulating testosterone. In sham-castrates, testis width was significantly reduced in hamsters housed in LD 6/18. In contrast, photoperiod and castration produced no detectable alterations in AVP immunoreactivity in various CNS sites including the bed nucleus of the stria terminales, the lateral septum and medial preoptic-anterior hypothalamus when measured by immunocytochemistry and radioimmunoassay of tissue punches. These data provide no evidence that AVP is regulated by either gonadal hormones or photoperiodic mechanisms in the Syrian hamster.

Peptidergic transmission in the brain. III. Hippocampal inhibition by the amygdala

The mechanism of arginine vasopressin (AVP) action in the rat hippocampus has been determined. The peptide activates inhibitory interneurons and constricts cerebral microvessels. In the whole animal, each of these direct actions has secondary consequences for the excitability of pyramidal cells. Recent studies have shown that a peptide similar to AVP mediates endogenous neurotransmission in the hippocampus. Here we report experiments showing that the endogenous peptide activates the same mechanisms as exogenously applied AVP. The endogenous AVP-like peptide has no effect on the presynaptic fiber volley, or on pure somatic and dendritic postsynaptic potentials. These results are taken to exclude presynaptic mechanisms as explanations for the peptide's action. The endogenously released peptide inhibits individual pyramidal cells in single unit recording and excites presumed interneurons, just as AVP itself is known to act. The endogenous peptide is released only by stimuli applied to a nucleus that contains immunoreactive AVP and projects to the hippocampus.

Intratesticular Control Of Steroidogenesis

Men are men because of testosterone, and the effects of this hormone are evident in virtually every organ or tissue in a normal adult man. Because testosterone is a classical endocrine hormone with effects throughout the body, many endocrinologists will have failed to realize that, in terms of its effects on fertility, the primary role of testosterone is not endocrine but paracrine, as it is the local action of testosterone on spermatogenesis which determines fertility. When looked at from this perspective it is logical to question the traditional endocrine teaching which states that testosterone secretion is controlled solely by pituitary luteinizing hormone (LH). Certainly, the levels of testosterone and LH in peripheral blood show a close relationship, but it is not the level of testosterone in peripheral blood which determines fertility. If the primary role of testosterone is within the testis, then it is not unreasonable to expect that local mechanisms may exist to regulate the intratesticular levels of this steroid. The object of this review is to examinecritically the evidence for such mechanisms, their possible nature and their physiological and clinical significance (if any). Before reviewing the data on intratesticular control of steroidogenesis it is essential to place it in perspective. To do this, three principal questions need to be answered: (I) Why might intratesticular mechanisms for local control of testosterone production be required? (2) What is the role (or roles) of testosterone within the testis? A proper understanding of how testosterone controls spermatogenesis is essential if the local regulation of testosterone production is to be evaluated from a physiological perspective. (3) What are the constraints or problems relating to studies on the intratesticular control of steroidogenesis? It is essential to understand the potential limitations of studies on this subject so that a reasoned interpretation of the results can be made. Most relevant data is derived from studies in uitro, and the relationship of such data to the situation in uivo is often difficult to establish.

Positive Feedback of Vasopressin on its Own Release in the Central Nervous System: in vitro Studies

Abstract In this paper evidence is shown that synthetic arginine vasopressin (AVP) can evoke marked in vitro release of endogenous immunoreactive AVP (I-AVP) from male rat septal and hypothalamic tissue superfused in vitro. The stimulatory action was dosedependent with a maximal amplification factor of 2.3 when using 14 pg of synthetic AVP as the stimulus. It was highly specific since only AVP was effective and not three closely related substances such as lysine vasopressin, oxytocin and a 4-9 C fragment of AVP. This reproducible effect of AVP required, however, effective concentrations of bacitracin (10(-4) to 10(-5) M) in the superfusion medium to inhibit aminopeptidase(s) capable of inactivating AVP. Lastly, the stimulatory action of AVP on its own release was not blocked by a V(1)-receptor antagonist of AVP but was blocked by a V(2)-antagonist. It is proposed that this novel and robust positive feedback of AVP on its own release may be involved in the mechanism of memory consolidation of certain behavioral tasks known to be affected by AVP.

Sex differences in hormonal responses of vasopressin pathways in the rat brain

Vasopressin (AVP) immunoreactivity in cells and projections of the bed nucleus of the stria terminalis (BST) and medial amygdaloid nucleus (MA) depends on gonadal steroids. In addition, the AVP projections from the BST show denser fiber staining in males than in females. To study whether these differences depend on different hormone levels in adulthood, male and female rats were gonadectomized and similarly treated with testosterone for 4 weeks prior to sacrifice. Immunocytochemistry showed that males had significantly more AVP-immunoreactive (AVP-IR) cells in the BST and significantly denser AVP-IR projections from this nucleus to the lateral septum, lateral habenular nucleus, and periaqueductal central gray than did females. The number of AVP-IR cells in the MA nucleus was not statistically different, but denser AVP-IR fiber networks were found in the MA and ventral hippocampus, which receives its input from the MA. No differences were found in the anteroventral portion of the periventricular nucleus and the dorsomedial nucleus of the hypothalamus that receive their AVP innervation from the suprachiasmatic nucleus. These results indicate that the sex difference in the steroid-sensitive AVP pathways depends on other factors besides circulating hormone levels in adulthood.

Content and contractile effect of arginine vasopressin in rat urinary bladder

The contractile response of normal male rat urinary bladders to exogenous arginine vasopressin (AVP) and the AVP content of normal and denervated bladders were investigated, In isolated detrusor strips, the maximal response to AVP was about 12% of the contraction elicited by KC1 (124 mM), and the EC 50 value was 1.03 ± 0.13 × 10 −8 M. The response to transmural nerve stimulation was not affected by the presence of AVP. Addition of an AVP receptor antagonist strongly reduced the response to exogenous AVP, but did not affect contractions in response to nerve stimulation. In normal bladders, the concentration of immunoreactive (ir) AVP was 29 ± 6.0 × 10 −15 mol/g. Three days after denervation the bladders had increased 2.4-fold in weight. At this time, the concentration of irAVP was not different from the control value, but the total content had increased significantly. Characterization of bladder irAVP by reverse-phase HPLC revealed that 66.5% of the total immunoreactivity eluted in the position of synthetic AVP. The results suggest a non-neuronal localization of bladder irAVP.

Vasopressin antagonist in early postoperative diabetes insipidus

23 patients without diabetes insipidus before transfrontal (hypothalamic) or trans-sphenoidal (pituitary) surgery were studied prospectively to investigate the pathogenesis of early postoperative diabetes insipidus. 12 patients who underwent trans-sphenoidal surgery and who did not develop diabetes insipidus were used as controls. All received prophylactic corticosteroid replacement. Blood samples were obtained immediately after operation, at the onset of diabetes insipidus, and 24 h later. Immediately after trans-sphenoidal pituitary surgery, plasma vasopressin (AVP) was raised but had fallen to subnormal concentrations by the onset of diabetes insipidus. After transfrontal hypothalamic surgery diabetes insipidus occurred sooner and was associated with high plasma AVP immunoreactivity—but the plasma showed no antidiuretic bioactivity and greatly attenuated the antidiuretic response to standard AVP. Early diabetes insipidus after hypothalamic surgery is associated with release of a substance, presumably an analogue, from the damaged hypothalamo-neurohypophyseal system, which acts as an antagonist to normal AVP activity; after trans-sphenoidal operations diabetes insipidus seems to be caused by failure of AVP release.