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Evidence for involvement of microtubules in the action of vasopressin in toad urinary bladder. I. Functional studies on the effects of antimitotic agents on the response to vasopressin.

The antimitotic agents colchicine, podophyllotoxin, and vinblastine inhibit the action of vasopressin and cyclic AMP on osmotic water movement in the toad urinary bladder. The alkaloids have no effect on either basal or vasopressin-stimulated sodium transport or urea flux across the tissue. Inhibition of vasopressin-induced water movement is half-maximal at the following alkaloid concentrations: colchicine, 1.8 X 10(-6) M; podophyllotoxin, 5 X 10(-7)M; and vinblastine, 1 X 10(-7)M. The characteristics of the specificity, time-dependence and temperature-dependence of the inhibitory effect of colchicine are similar to the characteristics of the interaction of this drug with tubulin in vitro, and they differ from those of its effect on nucleoside transport. Inhibition of the vasopressin response by colchicine, podophyllotoxin, and vinblastine is not readily reversed. The findings support the view that the inhibition of vasopressin-induced water movement by the antimitotic agents is due to the interaction of these agents with tubulin and consequent interference with microtubule integrity and function. Taken together with the results of biochemical and morphological studies, the findings provide evidence that cytoplasmic microtubules play a critical role in the action of vasopressin on transcellular water movement in the toad bladder.

Animals↗

Effects of peripherally injected vasopressin and des-glycinamide vasopressin on the extinction of a spatial learning task in rats.

An elevated eight-arm radial maze was employed to study the effects of neuropeptide administration on the spatial learning abilities of food-deprived rats. Following 18 days of reinforced training, each animal was briefly exposed to the maze with no food available in any of the eight food-cups. Immediately after this preliminary trial, animals were injected with a single subcutaneous dose of either saline, arginine vasopressin (AVP: 1.0 or 5.0 micrograms/kg), or an AVP analog with only weak endocrinological activity, des-gly-arginine vasopressin (DG-AVP: 1.0, 5.0 or 10.0 micrograms/kg). Additional extinction trials were conducted at 2, 4, 6 and 8 h post-injection. These tests consisted of individually placing an animal on the empty maze and recording the number of arms chosen in a 5-min period. In this situation, animals learn that food is no longer present in the maze and, consequently, extinguish responding. Vasopressin potentiated this radial maze extinction behavior while DG-AVP produced behavioral results directionally opposite to those predicted by a memory facilitation hypothesis. In a subsequent experiment, vasopressin had no effects on unconditioned locomotor activity measured 2 and 4 h post-injection. These results suggest that: vasopressin improved the learning that occurred during extinction of conditioned appetitive behaviors, these vasopressin effects on conditioned behavior were independent of any unconditioned, sedative or non-specific actions of the peptide, and peripheral endocrinological responses may be necessary to demonstrate memory-enhancing effects following peripherally administered AVP.

Animals↗

Conformational studies of oxytocin, lysine vasopressin, arginine vasopressin, and arginine vasotocin by carbon-13 nuclear magnetic resonance spectroscopy.

Oxytocin, arginine vasopressin, lysine vasopressin, arginine vasotocin, as well as their cyclic and acyclic analogs, were studied by carbon-13 nuclear magnetic resonance spectroscopy in deuterium oxide and deuterated dimethylsulfoxide. Fourier-transformed spectra were obtained at 25.16 MHz. The resonances of all carbon atoms have been assigned in both solvent systems; this includes tentative assignments of the carbonyl carbons. The spectra of arginine vasopressin and lysine vasopressin are essentially identical when compared in D(2)O or dimethylsulfoxide, but they differ from those of oxytocin. The spectrum of arginine vasotocin in D(2)O is intermediate between those of oxytocin and the vasopressins. These spectral differences are not only due to variations in constituent amino acids but are also a reflection of conformational differences of oxytocin, arginine vasotocin, and the vasopressins. All hormones are sensitive to changes in hydrogen ion concentration in both solvents; this was not observed with deamino analogs, which lack the terminal amino group.

Arginine↗

Renal response to arginine vasopressin during the oestrous cycle in the rat: comparison of glucose and saline infusion using physiological doses of vasopressin.

The renal response to arginine vasopressin in the rat has been shown to depend on reproductive status. However there is no consensus as to when the kidney is most responsive. The varying results could depend on the protocol and the dose of hormone used. A study has been performed, with physiological doses of vasopressin, comparing the responses during infusion of hypotonic saline and glucose. After an equilibration period of 150 min, conscious rats were infused on each of the four days of the oestrous cycle with either isotonic saline (0.077 M) or 0.14 M glucose for a control period of 45 min. Vasopressin was then infused at 10-40 fmol min(-1) for 1 h, followed by a recovery period of 90 min. Timed urine samples were collected for determination of volume, sodium concentration and osmolality. During the control period urine flow was greatest at oestrus and dioestrus day 2 and sodium excretion on dioestrus day 2 irrespective of the infusate. Vasopressin concentrations achieved lay within the physiological range and no difference was observed between the different days for a given dose. Infusion of vasopressin in both saline and glucose produced a dose-dependent antidiuresis, the greatest responses being seen of pro-oestrus and dioestrus day 2. It was only with the highest rate of infusion that a significant increase in sodium excretion was seen on each day of the cycle and the greatest responses were seen on pro-oestrus and dioestrus day 1 for both infusates. Thus the kidney shows the greatest response to physiological doses of vasopressin at pro-oestrus and dioestrus day 1 irrespective of the infusate employed.

Animals↗

Vasopressin-elicited refractoriness of the response to vasopressin in toad urinary bladder.

Incubation of the urinary bladder of Bufo marinus with high concentrations of vasopressin produces refractoriness to subsequent stimulation of water permeability by low concentrations of vasopressin. Development of refractoriness is directly dependent on concentration of vasopressin and duration of incubation with the hormone. Refractoriness develops in the absence of transepithelial water flow, is evident following a 2-h recovery period of incubation in hormone-free Ringer solution, and is reversed after prolonged incubation in hormone-free Ringer solution. Development and reversal of refractoriness is not altered by actinomycin D or cycloheximide. The steps at which refractoriness develops have been identified partially. Under different conditions, refractoriness involves: 1) reduced vasopressin-sensitive adenylate cyclase activity, 2) reduced epithelial cell cAMP accumulation in response to vasopressin the absence of demonstrable change in vasopressin-sensitive adenylate cyclase activity, cAMP phosphodiesterase activity, or loss of cAMP into the Ringer solution, and 3) refractoriness of water permeability response to exogenous cAMP.

3',5'-Cyclic-AMP Phosphodiesterases↗

Changes in the vasopressin content of discrete brain regions in response to stimuli for vasopressin secretion.

In order to better understand the function of vasopressin-containing axons which project to areas outside the hypothalamus, we measured vasopressin content in hypothalamic and extrahypothalamic brain regions following various periods of oral hypertonic saline or 1 week after pituitary stalk section. The supraoptic and paraventricular nuclei and nearly all of the brain regions examined which are known to receive vasopressin-containing axons from these nuclei showed parallel changes in vasopressin levels in response to both stimuli. In response to hypertonic saline there was an initial rise followed by a fall in vasopressin content. The suprachiasmatic and lateral septal nuclei, as well as the nucleus of the solitary tract, were unaffected by either stimulus. These results indicate that there are at least two functionally different vasopressin systems within the central nervous system, one of which is responsive to osmotic stimulation.

Amygdala↗

Effect of vertebral, carotid and intravenous infusions of lysine vasopressin on plasma vasopressin and cardiovascular function.

The cardiovascular and vasopressin-releasing effects of vertebral artery, carotid artery and intravenous (i.v.) infusions of lysine vasopressin (150 microU/kg X min) were studied in anesthetized dogs. Vertebral and carotid artery infusions of lysine vasopressin led to similar decreases in cardiac output as i.v. infusions. Heart rate, however, decreased to a greater extent with vertebral and carotid artery infusions of lysine vasopressin than i.v. infusions. There were no changes in either mean arterial blood pressure or the plasma vasopressin concentration. The results indicate that peripheral vasopressin: has a central effect to reduce heart rate; has a peripheral effect on the heart to reduce cardiac output, and probably does not feed back to inhibit its own release.

Animals↗

Effects of vasopressin-glycine and vasopressin-glycine-lysine-arginine on renal function in the rat.

The peptides vasopressin-Gly and vasopressin-Gly-Lys-Arg occur as part of the sequence of the vasopressin-neurophysin precursor molecule and may be released from the hypothalamus and/or pituitary. [8-Lysine]-vasopressin-Gly (LVP-Gly) and [8-lysine]-vasopressin-Gly-Lys-Arg were administered i.v. to conscious, water-diuretic rats. The renal effects of the peptides were assessed by comparison with the actions of [8-lysine]-vasopressin (LVP) which was administered to separate groups of rats. LVP-Gly and LVP-Gly-Lys-Arg were weakly antidiuretic. LVP-Gly-Lys-Arg was the more potent of the two peptides, but on a molar basis it only had about 10% of the antidiuretic activity of LVP. LVP-Gly and LVP-Gly-Lys-Arg at 10 pmol/h per 100 g body weight (equivalent to the maximal antidiuretic dose of LVP) slightly decreased (P less than 0.001) urine flow without causing significant changes in urine osmolality. LVP (10 pmol/h per 100 g body weight) promoted a marked natriuresis (P less than 0.001) but LVP-Gly and LVP-Gly-Lys-Arg were not natriuretic, even at the dose which was markedly antidiuretic (100 pmol/h per 100 g body weight). Osmolal output decreased at all doses during administration of the extended peptides, but was not significantly changed in the control group or by LVP. Inulin clearance was decreased by about 30% during administration of both LVP and LVP-Gly-Lys-Arg at 100 pmol/h per 100 g body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Vasopressin-sensitive kidney adenylate cyclase. Structural requirements for attachment to the receptor and enzyme activation: studies with vasopressin analogues.

Several vasopressin analogues were tested on pig kidney membranes for their ability to activate adenylate cyclase and to inhibit the binding of [8-lysine]vasopressin. Both the adenylate cyclase activation and hormonal binding were measured on the same enzyme preparation and under identical were measured on the same enzyme preparation and under identical experimental conditions. A preincubation period in the presence of hormone allowed the binding process to reach equilibrium. Peptide concentrations causing half-maximal adenylate cyclase activation (apparent Km) were, in the order of decreasing affinity:2.5 to 7.0 to 7.0 times 10-10 M [8-lysine] vasopressin, 3.1 to 4.0 times 10-9 M [8-arginine] vasopressin, 2.0 to 3.0 times 10-9 M [I,6-alpha-deaminocystathionine, 8-ornithine]vasopressin, 3.1 times 10-7 M des-9-glycineamide[8-lysine]vasopressin, 0.5 to 1.0 times 10-6 M[1,6-alpha-deaminocystathionine, 2-0-tert...

Adenylyl Cyclases↗

[1,6-alpha-aminosuberic acid,3-(p-azidophenylalanine), 8-arginine] vasopressin as a photoaffinity label for renal vasopressin receptors: an evaluation.

The photoreactive analog of vasopressin [1,6-alpha-aminosuberic acid,3-(p-azidophenylalanine), 8-arginine]vasopressin was labeled with tritium (specific radioactivity: 39 Ci/mmole). In the absence of UV-light, the tritium-labeled ligand retained a high binding affinity to the vasopressin receptor in plasma membranes from bovine kidney inner medulla (apparent dissociation constant KD: 1.4 X 10(-8) M). Renal plasma membranes were irradiated under conditions of a high ratio of specific versus non-specific binding of the reactive ligand. Sodium dodecyl sulfate gel electrophoresis after solubilization and reduction demonstrated the preferential labeling of a polypeptide with an apparent molecular weight of Mr = 32 000. A comparison with stained gels revealed that this protein is a minor constituent of the bovine kidney membrane. Our results suggest the 32 000-dalton polypeptide is either a component of the vasopressin receptor or that it is located in the immediate vicinity of the vasopressin binding protein.

Affinity Labels↗

Vasopressin reduces release from vasopressin-neurons and oxytocin-neurons by acting on V2-like receptors.

The effects of arginine vasopressin (AVP), and of the V2-AVP receptor agonist 1-deamino[8-D-arginine] vasopressin (DDAVP) on release from the vasopressin-neurons and oxytocin-neurons of Long-Evans rats were evaluated using specific radioimmunoassays for rat neurophysins. AVP (1 microgram, 1 nmol) or DDAVP (25 ng, 25 pmol) was administered i.p. to animals 1 h before they received an i.v. infusion of 18% saline at 10 microliters/100 g b. wt./min for 60 min. Both AVP and DDAVP decreased the responsiveness (slope) but not the sensitivity threshold of vasopressin-neurons to acute changes in plasma osmolality. Since the amounts of the peptides giving comparable decreases in responsiveness were directly related to their antidiuretic potencies, it is most probable that this influence is mediated through V2-like receptors. However, while ruling out a significant contribution of V1-type receptors, the data do not exclude involvement of other vasopressin receptors (e.g. V3-type receptors). Both AVP and DDAVP also appeared to have an inhibitory effect on release from oxytocin-neurons, but in this case they significantly altered sensitivity threshold but not responsiveness to acute changes in plasma osmolality. Because AVP produced a shift in sensitivity threshold larger than that by DDAVP when the peptides were used in amounts related to their antidiuretic potencies, our results suggest that the feedback influence of AVP on oxytocin-neurons is largely, although not entirely, exercised through V2-like receptors.

Animals↗

Interaction of a vasopressin antagonist with vasopressin receptors in the septum of the rat brain.

The ability of d(CH2)5-Tyr(Me)-arginine-8-vasopressin, an antagonist of peripheral pressoric (V1-type) vasopressin receptors, to label vasopressin binding sites in the septum of the rat brain was evaluated. Using crude membrane preparations from the septum, 3H-arginine-8-vasopressin (AVP) specifically labels a single class of binding sites with a Kd of 2.9 nM and maximum binding site concentration of 19.8 fmole/mg protein. 3H-Antag also labels a single class of membrane sites but with higher affinity (Kd = 0.47 nM) and lower capacity (10.1 fmole/mg protein) than 3H-AVP. The rank order of potency of various competitor peptides for 3H-AVP and 3H-Antag binding was similar. Oxytocin was 100-1,000 fold less potent than AVP in competing for binding with both ligands. 3H-AVP and 3H-Antag showed similar labeling patterns when incubated with septal tissue slices. Unlabeled Antag also effectively antagonized vasopressin-stimulated phosphatidylinositol hydrolysis in septal tissue slices.

Animals↗

Effects of desglycinamide9, (Arg8) vasopressin and vasopressin antiserum on the acquisition of intravenous cocaine self-administration in the rat.

The effect of the vasopressin neuropeptide desglycinamide9, (Arg8) vasopressin (DGAVP) on the acquisition of intravenous cocaine self-administration was studied. Rats were tested under conditions of reduced body weight in a continuous reinforcement operant procedure, during five daily 3 h sessions. Under these conditions, the rate of self-administration obtained with 0.125 and 0.25, but not 0.063 mg.ml-1 cocaine, exceeded the rate obtained with saline. Daily pretreatment with DGAVP (5 micrograms/rat, s.c.) decreased self-administration of 0.125 and 0.25 mg.ml-1 cocaine to the level obtained with saline, but had no effect on self-administration of 0.063 mg.ml-1 cocaine and saline. Using a similar procedure, it was shown that daily intracerebroventricular pretreatment with vasopressin antiserum significantly increased self-administration of 0.125 mg.ml-1 cocaine, without affecting self-administration of 0.063 and 0.25 mg.ml-1 cocaine and saline. The results support previous findings obtained with vasopressin neuropeptides in drug self-administration studies and suggest that DGAVP decreases the acquisition of cocaine self-administration by attenuating the reinforcing effects of cocaine and that endogenous vasopressin may be involved in the acquisition of cocaine self-administration.

Animals↗

The abnormal quinine drinking aversion in the Brattleboro rat with diabetes insipidus is reversed by the vasopressin agonist DDAVP: a possible role for vasopressin in the motivation to drink.

The Brattleboro rat with hypothalamic diabetes insipidus (BDI) has an abnormal aversion to drinking quinine-adulterated water compared with normal rats of the parent Long Evans (LE) strain. This BDI animal tolerates marked hypovolemia and decreased body weight in preference to drinking the quinine-adulterated fluid, indicative of a reduced motivation to drink. Acute or chronic treatment of BDI rats with desamino-8D arginine vasopressin (DDAVP) restored to normal their drinking response to quinine solution. Partial restoration of fluid turnover in BDI rats with hydrochlorothiazide, which has an antidiuretic effect in diabetes insipidus (when vasopressin is absent), failed to abolish the abnormal drinking response to quinine-adulterated solution in 8 out of 12 animals. In contrast, induction of diabetes mellitus in LE rats, which resulted in a marked polydipsia and polyuria even though vasopressin was still present, did not impair the drinking response to quinine solutions. These results suggest that the abnormal drinking response to quinine-adulterated fluid in BDI rats is reversed by treatment with the vasopressin V2-receptor agonist DDAVP but is unlikely to be a consequence of the restoration of fluid turnover to normal levels by a renal action. A possible central action involving vasopressin and the motivation to drink is discussed.

Animals↗

Short-photoperiod exposure reduces vasopressin (V1a) receptor binding but not arginine-vasopressin-induced flank marking in male Syrian hamsters.

In Syrian hamsters, socially relevant information is communicated with a form of scent marking known as flank marking. There is substantial evidence that arginine-vasopressin acting on V1a vasopressin receptors (V1aR) in the medial preoptic-anterior hypothalamic continuum (MPOA-AH) regulates the expression of flank marking. Previous studies have shown that the expression of flank marking is also influenced by the circulating concentrations of gonadal hormones. In hamsters housed in long 'summer-like' photoperiods (i.e. >12.5 h of light/day), castration reduces flank marking and administration of testosterone restores precastration levels of flank marking. When exposed to short 'winter-like' photoperiods (i.e. <12.5 h of light/day), hamsters undergo gonadal regression and the circulating levels of testosterone decline. Surprisingly, flank marking induced during social encounters is not reduced in hamsters exposed to short photoperiods despite the low circulating concentrations of testosterone. In the present study, it was hypothesized that reductions in testosterone, caused by exposure to short photoperiod, would not reduce the ability of vasopressin to stimulate flank marking by its actions in the MPOA-AH. The amount of flank marking induced by vasopressin injected into the MPOA-AH did not significantly differ between hamsters housed in long and short photoperiods; however, short photoperiod-exposed males had significantly less V1aR binding in the MPOA than long photoperiod-exposed males. These results support the hypothesis that the sensitivity of the MPOA-AH to vasopressin is not reduced in short photoperiod-exposed males, despite decreases in serum testosterone. However, by contrast to our predictions, short photoperiod-exposed males have significantly reduced V1aR binding in the MPOA-AH compared to long photoperiod-exposed males.

Animal Communication↗

Effects of the vasopressin V1 agonist [Phe2,Ile3,Orn8]] vasopressin on regional kidney perfusion and renal excretory function in anesthetized rabbits.

To test whether renal V1-receptors selectively influence blood flow in the renal medulla, we compared the effects of infusion of [Phe2,Ile3,Orn8]vasopressin (3-30 ng/kg/min) by the intravenous, renal arterial, and renal medullary interstitial routes in anesthetized rabbits. Intravenous [Phe2,Ile3,Orn8]vasopressin (30 ng/kg/min) reduced renal medullary perfusion (MBF) by 36 +/- 5% but did not significantly affect cortical perfusion (CBF). MBF was also reduced with the renal arterial (35 +/- 5%) and renal medullary interstitial (40 +/- 7%) routes but, in contrast to the intravenous infusion, CBF was also reduced, by 21 +/- 3% and 15 +/- 3%, respectively. Urine flow and sodium excretion were increased by [Phe2,Ile3,Orn8]vasopressin, and with direct intrarenal administration, this effect was similar for both the infused (left) and noninfused (right) kidneys. After a 20-min renal medullary interstitial infusion of [3H]norepinephrine, radiolabel concentration was approximately fivefold greater in the left medulla than in the left cortex. We conclude that [Phe2,Ile3,Orn8]vasopressin acts on V1-receptors to alter regional kidney blood flow and tubular salt and water handling. The V1-receptors involved are almost certainly within the kidney itself, but given the contrasting effects of the different infusion routes on MBF and CBF, we cannot exclude the possibility that some of the observed effects of [Phe2,Ile3,Orn8]vasopressin are mediated by activation of extra-renal V1-receptors.

Angiotensin II↗

Properties of [3H]1-desamino-8-D-arginine vasopressin as a radioligand for vasopressin V2-receptors in rat kidney.

[3H]1-Desamino-8-D-arginine vasopressin [3H] DDAVP was assessed as a radioligand for vasopressin V2-receptors by studying its membrane-binding characteristics and in vitro autoradiographic localization in rat kidney, a rich source of V2-receptors. [3H]DDAVP bound specifically to a single class of high affinity, low capacity sites in rat medullopapillary membranes. Specific [3H]DDAVP binding at 25 C reached equilibrium after 2 h of incubation and was saturable and linear with protein concentration up to 2.2 mg/ml protein. Saturation analysis gave an equilibrium dissociation constant (Kd) of 0.76 nM. Displacement of [3H]DDAVP binding by unlabeled arginine vasopressin (AVP) and related analogs gave the following order of potency, consistent with that expected for a V2-receptor: DDAVP approximately equal to AVP approximately equal to 1-desamino-AVP greater than lysine vasopressin greater than oxytocin greater than [1-(beta-mercapto-beta, beta-cyclopentamethylene-propionic acid, 2-(O-methyl)tyrosine]AVP. The C-terminal metabolites of AVP, (pGlu4Cyt6)AVP-(4-9), and (pGlu4Cyt6)AVP-(4-8) did not displace [3H]DDAVP binding. No degradation of [3H] DDAVP during incubation could be detected by HPLC analysis. In vitro autoradiography of [3H]DDAVP binding to rat kidney sections showed a very dense localization of displaceable binding over inner and outer medulla, with a much lower density in cortex, consistent with the known major localization of V2-receptors on renal collecting tubules. These studies suggest that [3H]DDAVP is a suitable radioligand for labeling V2-receptors and may be useful in the characterization of vasopressin receptor subtypes in a variety of tissues and in purification of the V2-receptor.

Algorithms↗

The vasopressin receptors colocalize with vasopressin in the magnocellular neurons of the rat supraoptic nucleus and are modulated by water balance.

Activity of the magnocellular neurons that synthesize vasopressin in the supraoptic and paraventricular nuclei of the hypothalamus is modulated by local release of the neuropeptide within the nuclei. V(1a) and V(1b) vasopressin receptor genes are expressed in these cells. The present study reports the localization of V(1a) and V(1b) receptors using multiple labeling immunocytochemistry. Both receptors are mainly located in vasopressinergic magnocellular neurons and colocalized with vasopressin in cytoplasmic vesicles dispersed throughout the cell. Possible functional modifications of the mRNA and protein levels of the V(1a) receptor, the major isoform, were also investigated by semiquantitative in situ hybridization and immunocytochemistry in rats submitted to reduced or increased water intake. V(1a) mRNA and receptor levels varied with water balance. V(1a) mRNA level dropped in rats submitted to high water intake. Conversely, dehydration up-regulated the V(1a) receptor content. These observations suggest that the pathways that regulate the expression of the genes encoding vasopressin and the V(1a) receptor are linked, which fits the present findings that the two partners are colocalized in cytoplasmic vesicles. Colocalization might explain how V(1) autoreceptors are controlled by cell activity and/or local concentration of vasopressin (released locally by the neurons themselves), allowing fine adjustment of magnocellular neuron activity.

Animals↗