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PubMed1992

The influence of oxytocin, vasopressin and their analogues on progesterone and testosterone production by porcine granulosa cells in vitro.

Effects of nonapeptide hormones and some of their chemical analogues on progesterone and testosterone production by culture of porcine granulosa cells have been investigated. Oxytocin (0.01-10 IU/ml), arginine-8-vasopressin (0.01-10 micrograms/ml), arginine-8-vasotocin (0.01-10 micrograms/ml) and, in a lesser degree, 2-0-methyl-tyrosine (deamino-1-karba)-oxytocin (0.01-10 micrograms/ml, but no 1-deamino-8-vasopressin (0.01-10 micrograms/ml) stimulated a progesterone surge. Testosterone production was significantly stimulated by oxytocin and inhibited by vasopressin or vasotocin additions. 2-0-methyl-tyrosine (deamino-1-karba)-oxytocin or 1-deamino-8-vasopressin had little or no effect on testosterone secretion. The present results suggest the existence of a direct influence of nonapeptide hormones on porcine ovarian progestagen and androgen production.

Animals↗

PubMedDate not supplied

[The effect of dehydration on the functional activity of the interrenal gland in adenohypophysectomized Rana catesbeiana frogs. A preliminary report].

A significant increase of the content of corticosterone in the blood collected from intravenous cannula or by intracardiac punction has been detected using radioimmunoassay in non-operated and adenohypophysectomized frogs Rana catesbeiana subjected to dehydration in 6.2% mannitol solution during 24 hours. The osmolality of the blood plasma of these animals also increases although less significantly than the growth of plasma corticosterone content. There is a tendency to substantial increase of plasma arginine-vasotocin level prior to the growth of corticosterone level, already after 6 hours of dehydration. Based on the present results and literature data, it is suggested that in adenohypophysectomized frogs lacking endogenous ACTH just the increase of blood arginine-vasotocin level results in a substantial activation of corticosteroid-producing cells of the interrenal gland and in the growth of plasma content of corticosterone.

Animals↗

PubMed1990

[Immunocytochemical study of the hypophyseal neural lobe of Natrix maura in dehydration].

The influence of the dehydration treatment on the hypophysial neural lobe of the water snake Natrix maura, has been investigated. Whereas control animals stayed in fresh water, experimental snakes were immersed in a hypertonic solution of sodium chloride (35%) for 48 h. All specimens were fixed by vascular perfusion with Bouin fluid and the pituitaries embedded in paraffin. The sections were stained through histochemical procedures and immunocytochemistry by means of antisera against bovine neurophysins, vasotocin and mesotocin. The intensity of the immunoreaction was measured by microdensitometry. The osmotic stress significantly decreases the amount of stainable neurosecretory material in the neural lobe as well as the immunoreactivity to antineurophysin and antivasotocin sera. Contrariwise, there is no clear decrease in the immunoreactivity to antimesotocin serum. These results suggest that the osmotic stress in Natrix maura elicited an increase in the release of vasotocin.

Animals↗

PubMed1990

[Efferent projections of "classical" peptidergic neurons of the neurosecretory system of the telencephalon in reptiles (Scincus scincus L. and Chalcides ocellatus Forskal; Lacertilia, Squamata].

In both species of lacertilian reptiles investigated, the peptidergic hypothalamic supraoptic and paraventricular nucleus project with efferents to the telencephalon, to caudal parts of the brain, and to the spinal cord. The marked system of efferents of the "classic" peptidergic neurosecretory nuclei to the telencephalon was mapped. The unlabeled peroxidase-antiperoxidase immunocytochemical procedure revealed at the light microscopical level neurophysin- respectively mesotocin- or vasotocin-containing exohypothalamic fibres in the septal area, in subcortical regions (ventral striatum and hypopallium), and in all layers of the cortical areas (medial, dorsal and lateral cortex). Within the different parts of the brain, there seems to be a characteristically quantitative ratio of the mesotocin and vasotocin fibres. The terminals of the exohypothalamic fibres contact perikarya and processes of neurons of the target regions intimately. In a selected area, peptidergic synapses could be demonstrated at the electron microscopical level using an ultrahistochemical method. It is assumed that the nonapeptides mentioned are released from the fibre terminals and then act as neurotransmitters/neuromodulators influencing different brain functions.

Animals↗

PubMed1989

Vasopressin-induced transfer via light vesicles of receptors and water channels from basolateral to apical membrane of toad bladder.

Toad bladder epithelial cells were homogenized and fractionated by Percoll density-gradient centrifugation. Binding of tritium-labeled vasopressin ([3H]AVP) was measured in surface membranes (SM), microsomes (M), and a 100,000 g (60-min) microsomal supernatant fraction (S). More than two-thirds of the total receptors were in S. Receptors in SM--but not in S--were tightly coupled to G-protein as suggested by inhibition of [3H]AVP binding by GTP. GTP-sensitivity of [3H]AVP binding was not altered by vasotocin (AVT) stimulation, although the distribution of receptors shifted from SM to S. Intact bladders, exposed on the serosal side to 1-desamino, 7-lysine-(4-azidobenzoyl), 8-arginine vasotocin (d7-N3-AVT) in the presence of UV light, exhibited a persistent hydroosmotic response compared to controls stimulated with photoaffinity analog in the dark. Cell fractions from the irradiated bladders showed a reduction in [3H]AVP binding in SM and S. Intact bladders, exposed on the mucosal side to d7-N3-AVT in the presence of UV light (while stimulated from the serosal side with AVP) exhibited a decrease in [3H]AVP binding in SM compared to controls without d7-N3-AVT.(ABSTRACT TRUNCATED AT 250 WORDS)

Affinity Labels↗

PubMedDate not supplied

[A bioassay for the testing of the oxytocic effect of hormone analogs of the neurohypophysis and the pineal body].

An improved bioassay for the testing of oxytocic compounds by the use of myometrium layer preparations has been developed and proved with synthetic oxytocin. The oxytocic activity of synthetic analogues was testes with this bioassay and compared to oxytocin. The myometrial layer preparation was demonstrated to be reliable, the vitality of the tissue is found for more than 8 hours. The sensitivity of the bioassay is found in the region of 10(-11) Mol/l oxytocin, the maximum of the stimulation of muscle strips varied from 5 X 10(-5) IU/ml to 10(-4) IU/ml oxytocin in the organ-bath. The concentration of the myometrium strips showed two different phases. Only the initial phase can be used for this bioassay. The calculation of the results was afforded planimetrically and by measuring of the concentration-maximum during the testing period. The synthetic hormone analogues [1-desamino-4-alpha-aminobutyric acid] lysine-vasotocin (2) and [4 alpha-aminobutyric acid] lysine-vasotocin had oxytocic activity and the myometrium was activated to contractions at 10(-8) Mol/1. The analogue 2 was 5-10 more active than 3. The contraction maximum for both analogues was found between 5 X 10(-6) and 5 X 10(-5) Mol/l. The induction of the concentration for both analogues varied with the factor 10(5).

Animals↗

PubMed1984

Effect of high hydrostatic pressure on sodium transport across toad skin.

The short-circuit current (Isc) was measured as an index of active net sodium transport across the isolated toad skin under various hydrostatic pressures up to 300 ATA. Upon compression, the base-line Isc increased transiently during the first 10 min by 10-15 microA/cm2 (congruent to 20%) and then decreased continuously, leveling off at 40 min under pressure. The latter decrease in base-line Isc (P less than 0.05 at all pressures) was pressure dependent, and its magnitude was 30 microA/cm2 (60% inhibition) at 300 ATA. Similarly, the transepithelial electric potential difference (PD) tended to increase slightly during the early phase of compression and decreased during the steady-state phase of compression. The transepithelial resistance (R), calculated from PD/Isc ratios, generally increased under pressure. The addition of vasotocin to the inside bathing medium resulted in an increase in Isc and PD and a reduction in R at all pressures. The magnitude of peak Isc response to vasotocin was 50-60 microA/cm2 at pressures up to 100 ATA, but decreased to 30 microA/cm2 at 200-300 ATA (0.05 less than P less than 0.10 as compared to the response at 1 ATA). On the other hand the stimulatory effect of 1 mM cyclic adenosine monophosphate (cAMP), added to the inside bathing medium, on Isc was not affected by pressure between 1 and 300 ATA. From these results it is postulated that the inhibition of base-line Na transport under high hydrostatic pressure may be primarily due to a decrease in the outer membrane permeability to Na rather than an inhibition of the Na-K-ATPase.

Animals↗

PubMedDate not supplied

[Hydro-osmotic activity of the cerebrospinal fluid in fetuses, children and adults].

The hydroosmotic activity of the cerebrospinal fluid in 38 persons of different ages and in 2 fetuses was investigated. In the fetal cerebrospinal fluid the hydroosmotic activity was undetectable. The highest hydroosmotic activity was observed in the cerebrospinal fluid of children aged 0 to 3 years (24.320 +/- 3530 microhydroosmotic units (mHOU/ml). The activity significantly decreased in the cerebrospinal fluid of children 7 to 10 years of age (13.184 +/- 2112 mHOU/ml, p < 0.01). The above activity was detected in 40% of the adult patients with different diseases and in all the cases of idiopathic diabetes insipidus. The hydroosmotic activity of both children and adults was sensitive to trypsin digestion. The data obtained suggest the presence of a basic peptide, probably arginine-vasotocin, in the cerebrospinal fluid studied. If this hypothesis is right, vasotocin occurres in the cerebrospinal fluid only after birth and decreases with age, with the exception of some cases of pathology.

Adult↗

PubMed1982

Preliminary results--isolation and identification of pineal neurohypophysial hormone-like activity.

We have initiated a project designed to isolate and identify the neurohypophysial peptides found in the bovine pineal gland. Our principle interest is to provide definitive molecular evidence in order to eliminate the conflict created by the present literature as to the presence of arginine vasotocin in the mammalian pineal gland. The pineals were extracted and chromatographed according to standard methods for the isolation of neurohypophysial peptides. All fractions were assayed for their ability to cause milk ejection using the in vivo assay described by Hadley et al. (1975). However, during the course of the isolation procedure a partially purified fraction was isolated that showed neurohypophysial hormone-like activity. According to tests run on parallel chromatographic columns, the substance responsible for the neurohypophysial hormone-like activity could not be oxytocin, arginine vasotocin or arginine vasopressin.

Animals↗

PubMed1980

Evidence of inactivation of pineal indoleamine N-acetyltransferase by protein thiol:disulfide exchange.

Pineal indoleamine N-acetyltransferase activity in homogenates is rapidly reduced at pH 6.8 by treatment with cystamine or arginine vasotocin. Other disulfides including glutathione disulfide, penicillamine disulfide, and N,N'-diacetylcystamine are either ineffective or less effective. The diamine analogous to cystamine, diaminohexane, is also ineffective. Inactivation by cystamine is accelerated at higher pH and is temperature- and time-dependent. It was also found that cystamine treatment inactivated N-acetyltransferase in intact pineal cells. Treatment with dithiothreitol reactivated the cystamine- or arginine vasotocin-inactivated enzyme formed in broken cell preparations and the cystamine-inactivated enzyme formed in intact cells. These observations indicate that pineal N-acetyltransferase can be inactivated by protein thiol:disulfide exchange; further research is required to ascertain whether this mechanism is of physiological significance.

Acetyltransferases↗

PubMed1999

Innervation and control of the adenohypophysis by hypothalamic peptidergic neurons in teleost fishes: EM immunohistochemical evidence.

Previous light microscopic studies have revealed neuropeptide-immunoreactive neurosecretory fibers in the teleostean neurohypophysis, and ultrastructural work has reported direct innervation of endocrine cells by the terminals of fibers penetrating the adenohypophysis. This paper reviews our recent data from ultrastructural, immunohistochemical, receptor localization, and superfusion studies, which suggest a role for neuropeptides in the control of teleost pituitary secretion. We have used a combination of pre- and post-embedding electron microscopic immunolabeling methods to determine which neuropeptides are present in fibers innervating the pituitaries of three species: Poecilia latipinna, Dicentrarchus labrax, and Clarias gariepinus. Numerous axon profiles with immunoreactivity for the neurosecretory peptides vasotocin and isotocin formed large Herring bodies and terminal-like boutons in contact with corticotropic, growth hormone, thyrotropic, and pars intermedia cells. Numerous melanin-concentrating hormone-immunoreactive fibers and scarcer neurotensin and corticotropin-releasing factor-immunoreactive fibers showed similar distributions, terminating close to pars intermedia and corticotropic cells. Somatostatin, cholecystokinin, galanin, substance P, neuropeptide Y, growth hormone-releasing factor, thyrotropin-releasing hormone, and gonadotropin-releasing hormone-immunoreactivities were found in small calibre fibers penetrating among growth hormone, thyrotropic, and gonadotropic cells. These morphological findings have been supplemented by autoradiographic studies, which showed the distribution of binding sites for vasotocin, isotocin, galanin, and neuropeptide Y ligands over specific groups of pituitary cells, and superfusion studies that showed growth hormone release was stimulated by growth hormone-releasing factor and thyrotropin-releasing hormone, but inhibited by somatostatin. The implications of these results for neuropeptidergic control of teleostean pituitary secretions are discussed.

Animals↗

PubMed1985

Pharmacological characterization of two specific binding sites for neurohypophyseal hormones in hippocampal synaptic plasma membranes of the rat.

Synaptic plasma membranes containing binding sites for tritiated oxytocin and arginine vasopressin were isolated from rat hippocampus. The binding parameters for oxytocin and vasopressin sites were determined and statistically analysed. The fitted curve for oxytocin binding was compatible with a model where the ligand interacts with two classes of receptors with different capacities and affinities. The sites with low binding capacity had an apparent dissociation constant at equilibrium of 1.8 nM and a maximal binding capacity of 17 fmol/mg protein. By contrast, the Scatchard plot failed to reveal a marked heterogeneity in the population of sites labelled with [3H]vasopressin with an affinity of 1.5 nM and a maximal binding capacity of 39 fmol/mg protein. The specificity of these binding sites, tested in competition experiments, revealed that these neurohypophyseal hormones labelled two distinct populations of sites. One population with a high affinity for vasopressin, oxytocin and vasotocin, the other population with a high affinity for vasopressin and vasotocin and a low affinity for oxytocin. Adenylate cyclase activity was not affected by arginine-vasopressin or oxytocin. These receptors are compared with previously characterized peripheral receptors.

Animals↗

PubMed1984

Renal handling of sodium chloride and its control in birds.

Avian kidneys show features of both mammalian and non-mammalian kidneys, possessing cortical reptilian-type (RT) and medullary mammalian-type (MT) nephrons, blood supplies from renal arterial and renal portal systems, and a primitive macula densa. To determine how these morphological characteristics contribute to unique renal functions, we examined first a possible functional link between the renal tubules and the preglomerular vasculature and, second, the function of the loop of Henle of the MT nephrons. Infusion of 5% NaCl (2.0 ml/kg/h) into the renal portal system of the pullet Gallus domesticus caused diuresis and natriuresis in the infused side, whereas infusion of the same dose into the systemic circulation showed no effect. Infusion of 10% NaCl at a higher flow rate into either the renal portal or systemic routes caused hypernaturemia and a prolonged antidiuresis, presumably due to a release of arginine vasotocin. Plasma renin activity (PRA) decreased during renal portal infusion of hypertonic saline, suggesting that increases in intratubular or peritubular NaCl levels may suppress PRA. The thick limb of the loop of Henle (TLH) isolated from the MT nephron of the quail Coturnix coturnix revealed a lumen-positive, furosemide-sensitive transepithelial voltage (Vt) that requires the presence of both Na and Cl. Net water flux (Jv) was nearly zero when the TLH was perfused and bathed with isosmotic solution. Net water flux increased only slightly and osmotic water permeability (Lp) was low when the osmotic gradient was imposed. Vasotocin altered neither Vt, Jv, nor Lp. Chloride efflux was higher than Cl influx, and net Cl absorption was comparable to that of the TLH of the mammalian kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Carrier-mediated transport of vasopressin across the blood-brain barrier of the mouse.

A brain to blood carrier-mediated transport system for arginine vasopressin (AVP) was investigated in mice after intraventricular injection of iodinated AVP and varying amounts of unlabeled material or candidate inhibitors. Residual activity in the brain detected after decapitation was used as the main determinant of transport activity. The half-time disappearance of iodinated AVP from the brain was 12.4 min, the Vmax was 1.41 nmol/g-min, and the apparent Km was 28.7 nmol/g. A 30-nmol dose of AVP, mesotocin, arginine vasotocin, pressinoic amide, pressinoic acid, tocinoic acid, and lysine vasotocin, but not oxytocin, lysine vasopressin, AVP free acid, tocinoic amide, Tyr-MIF-1, or cyclo Leu-Gly, significantly (P less than 0.05) inhibited the transport of iodinated AVP out of the brain. The 30 nmol dose of AVP had no effect on the transport of iodide or iodotyrosine out of the brain. High-performance liquid chromatography showed that 59.2% of the radioactivity found in the blood 2 min after an i.c.v. injection of labeled AVP eluted at the same position as labeled AVP compared with 68.8% of radioactivity eluting at that position after material was infused i.v. for 2 min. This indicates that intact peptide is transported across the blood-brain barrier and that most of the degradation of AVP occurs during circulation in the blood. Calculations based on the appearance of radioactivity in the periphery showed that 56.2% of the material injected centrally would have been transported into the periphery by 10 min. This appearance of material in the periphery was inhibited by the simultaneous injection of an excess of unlabeled peptide. Water loading significantly decreased the brain to blood transport rate of AVP by 40%. It is concluded that a saturable system exists for brain to blood transport of AVP and some structurally similar peptides.

Animals↗

PubMed1998

Identification of neurohypophysial hormone receptor domains involved in ligand binding and G protein coupling.

Chimeric vasopressin V2/OT receptors were constructed and investigated to identify receptor regions involved in ligand binding or G protein coupling. The fusion sites for one series of hybrid receptors were either located at the C-terminal end of the third extracellular domain or in the centre of the third transmembrane helix, respectively. In each pair of the resulting symmetrical hybrids only one receptor was able to bind arginine vasopressin (AVP) and/or oxytocin (OT). In both cases a major part of the vasopressin V2 receptor (V2R) was needed for ligand binding. A chimeric OT/V2 receptor including OT receptor (OTR) sequences from its N-terminus to the middle of transmembrane region three showed both high-affinity OT binding (Ki = 3 nM) and activation of the adenylyl cyclase. In contrast, a hybrid containing OTR sequences reaching from transmembrane helix five to its C-terminus showed the V2 receptor's ligand binding profile and was unable to couple to G alpha s. These results indicate (i) that the third and/or the fourth intracellular domain of the V2R are involved in G protein coupling and (ii) for high-affinity OT binding the N-terminal third of the OTR plays an important role. By detailed binding studies on a second series of chimeric V2/OT receptors with AVP, OT and the two hybrid hormone derivatives arginine vasotocin and oxypressin it was further demonstrated that the first two extracellular domains of the OTR are involved in binding to the C-terminal tripeptide of OT. Moreover, the third extracellular domain of the OTR is able to contact the cyclic part of OT and the fourth outer domain does not interact with the two variable amino acid residues of AVP and OT. Thus, the first three extracellular domains of the OTR provide an essential part of the OT binding site. The other part is most probably contributed by the OTR's transmembrane helices 3 and 4. Photoaffinity labeling and ligand binding studies demonstrated that the binding site for the OT antagonist d(CH2)5[Tyr(Me)2, Thr4, Orn8, Tyr9]vasotocin is located in the helices 1, 2 and 7. Our results provide evidence for the existence of separate domains of a peptide hormone receptor involved in binding and selectivity for agonists and peptide antagonists.

Animals↗

PubMed1984

Divergent neuropeptide evolutionary drifts between American and Australian marsupials.

Present-day marsupials, which are supposed to have arisen from a single stem diverging from the placental stem some 130 million years ago, exist only in the American and Australian continents. Comparison of the homologous genes and their protein products, which evolved under different environmental conditions, may provide arguments for either selective or neutral evolution. In contrast to Australian Macropodidae, which have peculiar neurohypophysial peptides, namely mesotocin and two pressor peptides, lysine vasopressin and phenypressin, the South American oppossum, Didelphis marsupialis, has oxytocin, lysine vasopressin, and arginine vasopressin. Because placental mammals have oxytocin and usually arginine vasopressin, and nonmammalian tetrapods have mesotocin and arginine vasotocin, it is assumed that (1) selective change of arginine vasotocin into arginine vasopressin occurred in mammalian ancestors and a subsequent gene duplication in the marsupial line gave rise to two pressor peptides with divergent neutral drifts in American and Australian groups, and (2) mesotocin of nonmammalian tetrapods has been preserved in Australian marsupials and reclaimed for milk-ejecting function whereas it has been converted into oxytocin in South American oppossums. The change of mesotocin into oxytocin seems neutral rather than selective.

Amino Acid Sequence↗

PubMed1989

Evidence that apomorphine induces penile erection and yawning by releasing oxytocin in the central nervous system.

Oxytocin (10 and 30 ng) injected into a lateral ventricle (i.c.v.) or the dopamine agonist apomorphine (40 and 80 micrograms/kg) injected subcutaneously induced repeated episodes of penile erection and yawning in male rats. The concomitant administration of the two substances did not produce any further increase in the number of penile erection and yawning episodes. Penile erection and yawning induced by either oxytocin or apomorphine were antagonized in a dose-dependent manner by i.c.v. pretreatment with the oxytocin antagonists [d(CH2)5Tyr(Me)-Orn8]vasotocin, [Pen1,Phe(Me)2,Thr4,Orn8]oxytocin and [d(CH2)5Tyr(Me)-Arg8]vasopressin, with a rank order of potency that follows their antioxytocic activity. (i.e. [d(CH2)5Tyr(Me)-Orn8]vasotocin congruent to [Pen1,Phe(Me)2,Thr4,Orn8]-oxytocin greater than [d(CH2)5Tyr(Me)-Arg8]vasopressin). The results suggest that apomorphine induces penile erection and yawning by releasing oxytocin in the central nervous system.

Animals↗

PubMed1970

Molecular evolution of the neurohypophysial hormones: The active peptides of a primitive bony fish Polypterus bichir.

Neurohypophysial hormones have been so far identified in Neopterygii and Crossopterygii but not in species of the bird sub-class of bony fishes, the Palaeopterygii. Isolation and chemical characterization of the active principles of a primitive bony fish, Polypterus bichir, have been performed. Isotocin (Ser(4)-Ile(8)-oxytocin) and arginine vasotocin (Arg(8)-oxytocin) have been identified. Because the same peptides were found in the recent Neopterygii, it can be deduced that neurohypophysial hormones have displayed a peculiar stability in the course of the evolution of bony fishes. However isotocin and vasotocin are replaced by oxytocin and vasopressins in mammals and therefore might be regarded as "old" molecules.

Journal Article↗