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PubMed1991

Oxytocin receptors in the mammary gland and reproductive tract of a marsupial, the brushtail possum (Trichosurus vulpecula).

Previous studies of marsupial lactation have shown that the milk-ejection reflex changes in sensitivity, being greater in small mammary glands sucked by small pouch young and lesser in larger glands supplying milk to larger young. The involvement of oxytocin receptors in these changes was examined in the brushtail possum Trichosurus vulpecula. Oxytocin receptors were measured in the mammary glands, uterus, and medial vaginal sacs by radioreceptor assay, using [3H]oxytocin as radioligand. In the mammary gland, a single oxytocin binding site was found with an affinity and receptor concentration of 0.81 +/- 0.41 l/nmol and 10.2 +/- 4.8 pmol/g tissue respectively (SD, 10 possums). Competitive displacement curves with related peptides and analogs showed the following order of specificity: d(CH2)5[Tyr(Me)2,Thr4,Tyr9-NH2]-vasotocin much greater than vasotocin greater than oxytocin = Arg-vasopressin greater than mesotocin greater than [Thr4,Gly7]-oxytocin = Lys-vasopressin greater than [deamino-Pen1, O-methyl-Tyr2, Arg8]-vasopressin greater than isotocin much greater than [d(CH2)5, D-Phe2, Ile4, Ala9-NH2]-AVP. [3H]Oxytocin did not bind to vasopressin receptors in the thoracic aorta. The concentration of oxytocin receptors was very high in small mammary glands (18.6 pmol/g tissue in a 2-g gland) and decreased logarithmically as the size of the mammary gland increased. It is suggested that the changes in the sensitivity of milk ejection to oxytocin is related to the concentration of mammary oxytocin receptors. The presence of oxytocin receptors in both uterus and median vaginal sacs extends previous observations and supports the hypothesis that in marsupial parturition, the uterus and medial vaginal sacs respond as a single functional unit to oxytocin.

Animals↗

PubMed1990

Non-mammalian "big" neurophysins--complete amino acid sequence of a two-domain MSEL-neurophysin from goose.

Vasotocin-associated neurophysin (MSEL-neurophysin) has been purified from goose neurohypophysis through molecular sieving and high-pressure reverse-phase liquid chromatography (HPLC). The protein has a molecular mass (measured by SDS-polyacrylamide gel electrophoresis) of 17 kDa in contrast to 10 kDa found for the mammalian MSEL-neurophysins. Complete amino acid sequence (131 residues) has been determined mainly through tryptic or staphylococcal proteinase peptides derived from carboxyamidomethylated neurophysin, isolated by HPLC and microsequenced. N- and C-terminal sequences have been established by Edman degradation or action of carboxypeptidase Y, respectively, applied on the native protein. Goose MSEL-neurophysin is homologous to the two-domain "big" MSEL-neurophysin previously identified in the frog. It appears that in non-mammalian tetrapods, namely birds and amphibians, the proteolytic processing of the pro-vasotocin involves only one cleavage, releasing the hormone moiety and a "big" neurophysin with two domains homologous to mammalian MSEL-neurophysin and copeptin, respectively. Comparison of the avian protein with its mammalian and amphibian counterparts reveals that the first half of the polypeptide chain is evolutionarily much less variable than the second and that the goose protein resembles the frog protein much more than the mammalian one.

Amino Acid Sequence↗

PubMed1996

Cloning and functional characterization of the amphibian mesotocin receptor, a member of the oxytocin/vasopressin receptor superfamily.

Mesotocin is the oxytocin-like hormone found in most terrestrial vertebrates from lungfishes to marsupials, which includes all non-mammalian tetrapods (amphibians, reptiles, and birds). It has the largest distribution in vertebrates after vasotocin found in all non-mammalian vertebrates and isotocin identified in bony fishes. In this study, we report the cloning and functional characterization of the cDNA for the mesotocin receptor (MTR) from the urinary bladder of the toad Bufo marinus. The cloned cDNA encodes a polypeptide of 389 amino acids that shows the greatest similarity to the teleost fish isotocin receptor and to mammalian oxytocin receptors with mutations in extracellular loops which are involved in ligand binding. When expressed in COSM6 cells, MTR exhibits the following relative order of ligand affinity: mesotocin > vasotocin = oxytocin > vasopressin > hydrin 1, isotocin, hydrin 2. Injection of MTR cRNA into Xenopus laevis oocytes induces membrane chloride currents in response to mesotocin, which indicates the coupling of the mesotocin receptor to the inositol phosphate/calcium pathway. This response is inhibited by an oxytocin antagonist, but not by a vasopressin antagonist specific for V2 vasopressin receptors. MTR mRNA is not only found in toad urinary bladder, but also in kidney, muscle, and brain tissue of the toad as revealed by northern blot analysis and reverse-transcriptase PCR. The results suggest a variety of function for mesotocin and its receptor including, in particular, an involvement in the regulation of water and salt transport.

Amino Acid Sequence↗

PubMedDate not supplied

A chemical method to isolate hypothalamic nonapeptides by coupling cyst(e)in with bimane.

Vasopressin, oxytocin as well as other active nonapeptides (vasotocin, etc) are difficult to isolate from tissues. Traditionally they were identified using cumbersome biological assays or immunoassays, commercially unavailable, and with some cross reactivity. Based on the fact that all these peptides have two Cysteines in their molecules we developed a simple, sensitive and specific method to detect them by HPLC after pre-column fluorescent derivatization with monobromobimane (mBBr). The peptides were separated on a Vydac C18 column after reduction with Tris (2-carboxyethyl) phosphine (TCEP) and derivatization with mBBr for 5 minutes in dark. Using this method we were able to detect specific peaks for arginine-, lysine-vasopressin, and vasotocin at levels as low as 10 pmol. The method can be used to detect other active peptides with cyst(e)ins in their molecule, as well.

Arginine Vasopressin↗

PubMed1970

Effect of neurohypophysial hormones on fluid movement across isolated bladder of Rana cancrivora, Rana temporaria and Bufo melanostictus.

1. The rate of fluid movement across the wall of isolated amphibian urinary bladder was estimated using hemi-bladders of the tropical euryhaline Rana cancrivora, the temperate R. temporaria and the tropical Bufo melanostictus.2. The rate of water outflow across the bladder walls was: Rana cancrivora, 4.8 mul./cm(2).hr; R. temporaria, 7.2 mul./cm(2).hr; Bufo melanostictus, 3.7 mul./cm(2).hr.3. When neurohypophysial peptides were added to the serosal solution the rates of water outflow were increased; dose-response curves were prepared relating the augmented rate of fluid movement to the concentration in the bathing fluid of vasopressin, oxytocin or vasotocin.4. The potencies of the peptides in respect of bladders of each species were:Vasopressin, B. melanostictus:Rana temporaria:R. cancrivora, 500:20:1.Oxytocin, R. temporaria:B. melanostictus:Rana cancrivora, 100:5:1.5. The ratio of sensitivity of the bladder of each species to the presence of the different peptides was:R. cancrivora, vasotocin:oxytocin:vasopressin, 1000:5:1.R. temporaria, oxytocin:vasopressin, 15:1. Bufo melanostictus, oxytocin:vasopressin, 1:30.6. The effect of extract of the pituitary gland of Rana cancrivora was examined on R. cancrivora bladder. It had a dose-response curve similar to the dose-response curve of vasotocin.7. The vasotocin content of the pituitary gland of R. cancrivora was estimated(a) from the dose-response curves using R. cancrivora bladder,(b) by a three-point assay using R. cancrivora bladder and(c) by its effect on water uptake across the skin of Bufo melanostictus. One pituitary gland of Rana cancrivora was found to contain about 0.1 mug vasotocin.8. The urinary bladder of R. cancrivora was less responsive to neurohypophysial peptides than the bladder of R. temporaria or Bufo melanostictus.9. The hormonal content of the pituitary gland of Rana cancrivora was smaller than that found in other amphibians.

Animals↗

PubMed1984

Electrophysiological evidence for facilitatory control of oxytocin neurones by oxytocin during suckling in the rat.

Antidromically identified paraventricular neurones were recorded simultaneously with intramammary pressure in urethane (1.2 g/kg) anaesthetized rats during suckling. The correlation of the firing pattern of these neurones with milk ejection enabled distinction between oxytocin and vasopressin neurones. Oxytocin neurones displayed a short (2-6 s) characteristic high-frequency burst of spikes. This activation probably occurred simultaneously in all oxytocin neurones 12-18 s before milk ejection and was regular in both frequency and amplitude (total number of spikes). The role of neurohypophysial peptides and analogues in the control of these characteristics was studied. Injecting 10 pg, 100 pg and 1 ng of oxytocin into the 3rd ventricle increased background activity of slow-firing oxytocin neurones (less than 3 spikes/s) and had a strong dose-dependent facilitatory effect on the milk ejection reflex, increasing both the amplitude and frequency of neurosecretory bursts. No effect was observed on non-neurosecretory neurones. Such injection also triggered the milk ejection reflex when it had not appeared an hour after suckling began. Oxytocin did not itself induce neurosecretory activation, which only appeared if the young rats were sucking. Injecting oxytocin into the lateral ventricle was less effective than into the 3rd ventricle. No effect was observed after injection into the venous blood or into the 4th ventricle, which suggested that oxytocin acts in the hypothalamus. Injecting mesotocin or isotocin into the 3rd ventricle had a facilitatory effect similar to that of oxytocin but vasopressin, vasotocin, MIF I (pro-leu-gly-NH2, terminal triplet oxytocin) or bovine neurophysins I and II did not modify neurosecretory activation or the milk ejection pattern. Injecting an oxytocin antagonist, ([1(beta-mercapto-beta, beta cyclopentamethylene propionic acid), 8-ornithine] vasotocin, d(CH2)5OVT) into the 3rd ventricle decreased milk ejection frequency and considerably delayed the reappearance of the first milk ejection. This resulted from a decrease in both frequency and amplitude of neurosecretory bursts, which were too small to induce detectable oxytocin release. Moreover, d(CH2)5OVT suppressed the facilitatory effect of exogenous oxytocin. Under normal conditions, endogenous oxytocin seemed to be involved in the control of neurosecretory activation. Injecting 1 ng oxytocin or 1 or 10 ng vasopressin into the 3rd ventricle did not modify the firing pattern of vasopressin neurones whether activated by hyperosmotic stimulation (1 ml NaCl, 9% solution (w/v) I.P.) or not.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗

PubMed1980

Comparison of transcutaneous permeability in skins of larval and adult salamanders (Ambystoma tigrinum).

The electrical properties and transcutaneous movements of Na, Cl, and water were compared (in vitro) in skins of larval and adult forms of Ambystoma trigrinum. Larval skin had a mean transcutaneous potential difference of 6 mV (inside positive) in adults it was 50 mV. Short-circuit current (Isc) was, respectively, about 2 microA x cm-2 and 20 microA x cm-2. Electrical resistances were similar. Passive effluxes of Na and Cl were similar in both forms but Na influx (active direction) was much greater in the adult. Diffusional permeability to water was less in the larval salamander skin. Influx of Na and Isc were increased by vasotocin in the adult but not larval skin. Water permeability was unaffected by vasotocin in either form. The properties of the premetamorphic skin are compared to those of two other urodele amphibians.

Age Factors↗

PubMed1987

Hormonal regulation of hepatic glycogenolysis in the carp, Cyprinus carpio.

Carp (Cyprinus carpio) liver maintained normal glycogen content and enzyme complement for several days in organ culture. Epinephrine-stimulated glycogenolysis, phosphorylase activation, and cyclic AMP (cAMP) accumulation in a concentration-dependent manner with EC50s of 100, 100, and 500 nM, respectively. These actions were blocked by the beta-adrenergic antagonist, propranolol, but not by the alpha-adrenergic antagonist phentolamine. Glycogenolysis and tissue cAMP were uninfluenced by 10(-6) M arginine vasotocin, arginine vasopressin, lysine vasotocin, lysine vasopressin, mesotocin, or oxytocin, but were slightly increased by 10(-5) M isotocin and slightly decreased by 10(-6) M angiotensin II. [125I]-iodocyanopindolol (ICP), a beta-adrenergic ligand, bound to isolated carp liver membranes with a KD of 83 pM. Maximum binding of 45 fmol/mg protein was at 600 pM. Propranolol, isoprenaline, epinephrine, phenylephrine, norepinephrine, and phenoxybenzamine displaced ICP with KDs of 100 nM, 2, 20, 20, 60, and 200 microM, respectively. The alpha-adrenergic antagonists, yohimbine and prazosin, showed no specific binding. These data provide evidence that catecholamines act via beta-adrenergic receptors in carp liver and that alpha-adrenergic receptors are not present. Vasoactive peptides play no significant role in regulation of carp liver glycogenolysis.

Alanine Transaminase↗

PubMed1992

Pharmacological characterization of V1a vasopressin receptors in the rat cortical collecting duct.

Vasopressin receptors in distal segments of the rat nephron were identified in isolated tubules using two labeled ligands: the [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine,4-threonine,8-ornithine,9-125I-tyrosylamide]- vasotocin [125I-d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT] and the linear analogue, Phaa1,D-Tyr(Me)2,Phe3,Gln4,Asn5,Arg6, Pro7,Arg8,125I-Tyr-NH2(9) [125I-Tyr-NH2(9)-linear antagonist (LA)-V1a)]. Specific 125I-d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]-OVT binding to cortical collecting ducts (CCD) was saturable with incubation time and dose, reversible after elimination of free ligand, and characterized by the following rank order for recognition of vasopressin analogues: desGly9-d-(CH2)5-[Tyr(Et)2,Val4]arginine vasopressin (AVP) greater than or equal to d(CH2)5[Tyr-(ET)2,Val4]AVP greater than or equal to AVP greater than or equal to d(CH2)5[Tyr(Me)2]AVP = 1-desamino-8-D-arginine vasopressin (DDAVP) greater than or equal to Tyr-NH2(9)-LA-V1a greater than [8-arginine]vasotocin (AVT) greater than d(CH2)5[Tyr(Me)2, Thr4,Tyr-NH2(9)]OVT greater than oxytocin (OT) greater than [Phe2,Orn8]VT much greater than [Thr4,Gly7]-OT. Scatchard plots of dose-dependent 125I-Tyr-NH2(9)-LA-V1a binding to medullary thick ascending limbs (MTAL), CCD, and outer medullary collecting ducts (OMCD) revealed the presence of high- and low-affinity binding sites corresponding to V1a and V2 vasopressin receptors, respectively; the densities of V1a receptors are approximately 20% of the total number of vasopressin receptors in CCD and 5% in MTAL and OMCD.

Animals↗

PubMed1994

Prolactin-releasing activity of neurohypophysial hormones: structure-function relationship.

Oxytocin (OT) and arginine vasopressin (AVP) have been reported to release PRL both in vivo and in vitro. The objectives of this study were 1) to compare the potencies of the PRL-releasing activities of OT and TRH using cultured anterior pituitary (AP) cells, and 2) to assess the PRL-releasing activity of naturally occurring neurohypophysial hormones and selected analogs. AP cells were incubated with peptides for 15 min, and medium PRL concentrations were determined by enzyme-linked immunosorbent assay. OT at 25, 100, and 400 nM increased PRL release by 110%, 175%, and 270%, respectively; higher concentrations (1600 and 6400 nM) did not cause a further increase in PRL release. TRH was 5-10 times more potent than OT on a molar basis. GH3 cells, a somatommamotroph tumor cell line, did not respond to OT and related compounds, but showed a similar responsiveness to TRH as AP cells. Twelve neurohypophysial peptides and selected analogs were incubated with AP cells, and their relative PRL-releasing activities were compared. OT and arginine vasotocin (AVT) showed the highest PRL-releasing activity. T4-G7-oxytocin, mesotocin, isotocin, lysine vasotocin, and AVP showed a moderate PRL-releasing activity, whereas, lysine vasopressin, desmopressin, tocinoic acid, pressinoic acid, and oxytocin free acid showed very low or no PRL-releasing activity. Coincubation of OT, AVT, or AVP with a specific OT receptor antagonist abolished their PRL-releasing activity. We conclude that 1) OT and related peptides are capable of stimulating PRL release in vitro, but their potencies are significantly lower than that of TRH; 2) unlike primary AP cells, GH3 cells are unresponsive to OT and related peptides; 3) AVT and AVP probably stimulate PRL release by acting via an OT receptor; and 4) the amino acid residues in positions 3 and 8 in the peptide chain and an amidated C-terminus are critical for the PRL-releasing activity of the neurohypophysial peptides.

Amino Acid Sequence↗

PubMed1989

Gonadotrophin-releasing activity of neurohypophysial hormones: II. The pituitary oxytocin receptor mediating gonadotrophin release differs from that of corticotrophs.

Neurohypophysial hormones stimulate gonadotrophin release from dispersed rat anterior pituitary cells in vitro, acting through receptors distinct from those which mediate the secretory response to gonadotrophin-releasing hormone (GnRH). The LH response to oxytocin was not affected by the presence of the phosphodiesterase inhibitor, methyl isobutylxanthine, but was diminished in the absence of extracellular calcium and was progressively increased as the calcium concentration in the medium was raised to normal. In addition, the calcium channel antagonist, nifedipine, suppressed oxytocin-stimulated secretion of LH. It is likely that the mechanisms of LH release induced by GnRH and neurohypophysial hormones are similar, although stimulation of gonadotrophin secretion is mediated by separate receptor systems. Oxytocin was more active than vasopressin in releasing LH, but less active in releasing ACTH. The highly selective oxytocin agonist, [Thr4,Gly7]oxytocin, elicited concentration-dependent secretion of LH but had little effect on corticotrophin secretion. The neurohypophysial hormone antagonist analogues, [d(CH2)5Tyr(Me)2]vasopressin, [d(CH2)5Tyr(Me)2,Orn8]vasotocin and [d(CH2)5D-Tyr(Et)2Val4,Cit8]vasopressin, inhibited the LH response to both oxytocin and vasopressin. However, [d(CH2)5Tyr(Me)2]vasopressin was much less effective in inhibiting the ACTH response to the neurohypophysial hormones, and [d(CH2)5Tyr-(Me)2,Orn8]vasotocin and [d(CH2)5D-Tyr(Et)2,Val4,Cit8]vasopressin exhibited no inhibitory activity against ACTH release. Thus, agonist and antagonist analogues of neurohypophysial hormones display divergent activities with regard to LH and ACTH responses, and the neuropeptide receptor mediating gonadotroph activation is clearly different from that on the corticotroph. Whereas the corticotroph receptor is a vasopressin-type receptor an oxytocin-type receptor is responsible for gonadotrophin release by neurohypophysial hormones.

1-Methyl-3-isobutylxanthine↗

PubMed2000

[Ultrastructure and elemental composition of frog bladder granular epithelial cells in normal state and upon stimulation of water transport].

Changes in the frog urinary bladder granular cell ultrastructure were analysed in parallel with those in element composition of these cells after induction of water transport across the urinary bladder wall. Two ultrastructural (ultrathin section and freeze-fracture) methods were used in addition to two methods of object preparation for electron microprobe analysis--freeze-drying and freeze-substitution. It has been shown that arginin-vasotocin stimulation of osmotic water flow across the urinary bladder wall causes certain morphological changes in the granular cells: decrease in electron density of the cytoplasm, depolymerization of the apical submembrane layer of actin microfilaments, increase in the number of sites of specific granules and apical membrane fusion, emergency of intramembrane particle aggregates in the apical membrane P-face. The quantitative electron microprobe analysis made it possible to reveal a statistically significant increase in sodium and calcium concentration and fall in that of potassium and chlorine in granular cells after water transport stimulation. A concentration gradient of sodium and potassium ions was seen to appear along the apical-basal axis in the cytoplasm of granular cells. Possible association between the obvious morphological transformations in granular cells and changes in their elemental composition has been discussed, in addition to some regulatory significance of calcium concentration increase in granular cells after arginin-vasotocin-induced osmotic water transport.

Animals↗

PubMed1985

[Vasopressin and oxytocin receptors in the central nervous system of the rat].

Synaptic plasma membranes containing binding sites for (3H) oxytocin and (3H) arginine vasopressin were isolated from rat amygdala, olfactory bulb and hippocampus. In the hippocampus, two specific binding sites have been characterized: an "oxytocic" binding site, which has a high affinity for oxytocin, arginine vasopressin and arginine vasotocin, and a "vasopressic" binding site, which has a high affinity for arginine vasopressin, arginine vasotocin and a low affinity for oxytocin. The specificity of these binding sites were tested in competition experiments. The affinity of different antidiuretic and vasopressic analogues for the vasopressic site was similar to that observed for the V1 type of vasopressin receptors present in the hepatocytes and vascular smooth muscle cells. The affinity of several analogues for the oxytocic site shows some similarities with their corresponding relative activities in increasing the firing rate of non pyramidal neurones in hippocampal slices. Arginine vasopressin and oxytocin did not change the activity of adenylate cyclase present in the hippocampal synaptic plasma membranes. The properties of these specific binding sites for the neurohypophyseal hormones are compared with the receptors present on the peripheral targets.

Adenylyl Cyclases↗

PubMed1986

Mechanism of action and structural requirements of vasopressin analog inhibition of transepithelial water flux in toad urinary bladder.

Vasopressin, vasopressin analogs, forskolin and 8-bromo-cyclic AMP (8Br-cAMP) were studied for their effects on transepithelial water flux in toad urinary bladder. Arginine vasopressin, arginine vasotocin, oxytocin, desamino-8-D arginine vasopressin, forskolin and 8Br-cAMP stimulated hydro-osmotic water flux in a dose-dependent fashion. The rank order of potency was arginine vasotocin greater than arginine vasopressin greater than oxytocin greater than desamino-8-D-arginine vasopressin greater than forskolin greater than 8Br-cAMP. The vasopressin analogs [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-methyl)tyrosine,8-arginine]vasopressin (SK&F 100273), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-methyl)tyrosine,4-valine,8-arginine]vasopressin (SK&F 100501), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-D-tyrosine,4-valine,8-arginine]vasopressin (SK&F 100885), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-ethyl)tyrosine,4-valine,8-arginine]vasopressin (SK&F 100398), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-D-isoleucine,4-valine,8-arginine]vasopressin (SK&F 101485), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-ethyl)-tyrosine,4-valine,8-arginine]vasopressin (SK&F 101498), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-ethyl)D-tyrosine,4-valine,8-arginine,9-desglycine]vasop ressin (SK&F 101926) and [1-(beta-mercapto-beta-beta-cyclopentamethylene propionic acid),2-D-phenylalanine,4-valine,8-arginine] vasopressin (SK&F 101071) antagonized arginine vasopressin-stimulated water flux and displaced the agonist dose-response relationship to the right in a parallel fashion. The most potent antagonists were those having the (O-ethyl)-D-tyrosine substitution at position 2. None of the antagonists tested had any effect on 8Br-cAMP-stimulated water flux at concentrations up to 10(-6)M.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗

PubMedDate not supplied

Effects of melatonin on maturational indices of the brain in rats.

In order to investigate the effects of the pineal indole melatonin upon the brain maturation, groups of 40 Wistar rats were treated (for 6 days) either with melatonin (100 micrograms/0.1 ml) or with diluent alone (0.1 ml). The brain development was investigated by following the weight, total lipids as well as the water content of the brain in rats of 12, 30, 40 days or of adult age. Whether in rats of 12 days of age, melatonin produced no significant effects on brain maturation, beginning with the 30th day of age, it increases the weight, total lipids as well as the water content of the brain. It is concluded that, since these effects are opposite to those reported for the pineal hormone arginine vasotocin, not only as aspect but also in the age of their appearance, the maturation of the rat brain could be under a double tonic control, one inhibitory (the fetal and neonatal pineal arginine vasotocin) and another stimulatory (the postnatal pineal melatonin).

Animals↗

PubMed1985

Regulation of lymphokine production by arginine vasopressin and oxytocin: modulation of lymphocyte function by neurohypophyseal hormones.

The neurohypophyseal hormones arginine vasopressin (AVP) and oxytocin are capable of replacing the interleukin 2 (IL 2) requirement for T cell mitogen induction of gamma-interferon (IFN-gamma) in mouse spleen cell cultures. The structural basis for the helper signal by these hormones resides in the six N-terminal amino acids of AVP based on the relative ability of AVP, oxytocin, vasotocin, and pressinoic acid (AVP six N-terminal amino acid peptide) to help in IFN-gamma induction. AVP and pressinoic acid provide maximal help at 10(-10) M, while oxytocin and vasotocin with isoleucine at position three in place of phenylalanine are 10-fold less effective. An AVP competitive antagonist of vasopressor activity blocks the AVP helper signal for production of IFN-gamma, while having no effect on IL 2 help. This suggests that the AVP helper signal operates via binding to an AVP vasopressor-type receptor on lymphocytes.

Animals↗

PubMed1963

STRUCTURAL REQUIREMENTS FOR THE ACTION OF NEUROHYPOPHYSEAL HORMONES UPON THE ISOLATED AMPHIBIAN URINARY BLADDER.

The response of the isolated amphibian urinary bladder to thirty-four structural analogs of arginine vasotocin was determined in an effort to define the physiological significance of specific structural groups on the hormone molecule. All but one of the analogs tested possessed full intrinsic activity in this system but varied greatly in their affinity for the receptor site. An analysis of the effect of changes in hydrogen ion concentration upon the response of the bladder to oxytocin was performed in order to determine the number and nature of the ionizable groups involved in hormone receptor interaction. Two ionizable groups with apparent pK's of 7.1 and 7.75 were found to be important in determining the magnitude of the hormonal response. On the basis of the results it was postulated that hormone-receptor interaction can be considered a two-step process: (a) The binding or attachment of hormone to receptor site through ionic, hydrogen, and hydrophobic bonds and (b) a disulfide interchange reaction between hormonal disulfide and receptor sulfhydryl. The latter step is considered to be the reaction which initiates the chain of events leading to the observed change in permeability.

Amphibians↗

PubMed1999

Development of sexually dimorphic vasotocinergic system in the bed nucleus of stria terminalis in chickens.

The bed nucleus of stria terminalis (BnST) of the domestic fowl contains two groups of parvicellular vasotocinergic neurons that are sexually dimorphic. In adult cockerels, arginine vasotocin (AVT) synthesis is well expressed in the dorsolateral and ventromedial portions of the BnST, whereas in corresponding brain areas of hens, AVT synthesis is completely lacking. In the present study, in situ hybridization and immunocytochemical methods were used to compare the ontogeny of sexually dimorphic AVT gene expression in the BnST of male and female chickens from day 12 of embryonic development (E12) until the onset of sexual maturation. By E12, both parvicellular groups of AVT-immunoreactive (AVT-ir) perikarya in the developing BnST can be distinguished in some males, whereas in females their presence is questionable. A quantitative analysis, beginning at E14, showed that the parvicellular dorsolateral portion of the BnST of male embryos had more AVT perikarya compared with females. In contrast, no evident sex difference in distribution pattern and number of AVT mRNA containing neurons in this BnST portion was observable by in situ hybridization at E15. At E18, as well as on the first and second days posthatch (D1 and D2), no differences in the number of AVT synthesizing cells and intensity of immunoreactive staining in male versus female chickens were found. Between D2 and D7, the number of AVT-ir cells in the BnST declined rapidly in both sexes until it disappeared completely in females before D35. In males, another increase in sexually dimorphic AVT-ir cells and innervation of the lateral septum was associated with the onset of puberty and fully matched a pattern observed in adult fowls. These results demonstrate that the sexually dimorphic part of the AVT system undergoes sexual differentiation during early stages of ontogeny.

Animals↗