Vasotocin Content Research Articles

Plasma Arginine-Vasotocin and Hydroosmotic Status of the Terrestrial Pit ViperBothrops jararaca

Peaks corresponding to arg-vasotocin obtained by HPLC from Sep-Pak C18 column extracts ofBothrops jararacaplasma were identified by radioimmunoassay and amino acid analysis. Plasma vasotocin and protein levels, osmolality, andl-cystine-di-β-naphthylamidase were also compared in snakes under normal hydration conditions with or without chronic administration of vasotocin or in the presence of chronic hydroosmotic challenges. Sep-Pak C18 and radioimmunoassay were validated for the extraction and determination of this peptide, respectively (about 80% recovery). EDTA presented a protective action on this recovery compared to the use of heparin as anticoagulant for snake blood. A reduction of vasotocin content related to the time of incubation of this peptide added to snake plasma was detected by radioimmunoassay. Snake plasma activity also onl-cystine-di-β-naphthylamide indicated that this vasotocin-destroying effect was due to hydrolysis by a cystine-aminopeptidase-like activity. Plasma levels of vasotocin revealed an unexpected dispersion and absent correlation with plasma levels of osmolality. Measurable vasotocin in a large number of snakes associated with lower levels ofl-cystine-di-β-naphthylamidase in acute than in chronic salt loading suggested the role of this enzyme activity in long-term regulation of the vasotocin system in this snake.

Changes in arginine vasotocin content in the pituitary of the medaka ( Oryzia latipes) during osmotic stress

Changes in the arginine vasotocin (AVT) neurons of the medaka, Oryzias latipes, during osmotic stress were studied by means of immunohistochemistry and radioimmunoassay. AVT neurons were identified by their immunoreactivity to anti-arginine vasopressin serum, which crossreacts with AVT. When freshwater (FW)-adapted fish were transferred to seawater (SW), the number of immunoreactive magnocellular neurons decreased, while the cell nuclear size increased. AVT content in the pituitary significantly decreased 2 hr or 1 day after transfer to SW, but returned to approximately the initial level 1 week after transfer. However, when SW-adapted fish were transferred to FW, the number of immunoreactive magnocellular neurons increased from 1 hr after readaptation to FW, but the cell nuclear size failed to show significant changes. AVT content in the pituitary significantly increased 1 or 2 hr after transfer. These results seem to indicate that AVT secretion in the medaka was temporarily accelerated by exposure to SW and inhibited immediately after transfer to FW.

Diel variations in arginine vasotocin content of goldfish brain and pituitary: Effects of photoperiod and pinealectomy

Arginine vasotocin (AVT) content was determined in the telencephalon, the hypothalamus, and the pituitary gland of sham-operated and pinealectomized goldfish subjected to 20° and 12 12LD or 24DD photoperiods in winter or spring. The tissues collected at 1000 or 2200 hr were homogenized and extracted in acetic acid. Hypothalamic and telencephalic AVT content, determined by radioimmunoassay, fluctuated throughout the light-dark cycle; AVT content was higher at 2200 than at 1000 hr under the 12 12LD photoperiod. No fluctuations were detected in pituitary AVT content. Telencephalic AVT did not fluctuate under constant darkness, and hypothalamic AVT increased and pituitary AVT decreased compared to the AVT content detected in the 12 12LD groups. No significant effects of pinealectomy or season on AVT levels in the telencephalon, hypothalamus, and the pituitary were evident. The results indicate that AVT content within the preoptico-neurohypophyseal system of the goldfish fluctuate within 24-hr periods and that photoperiod has an effect on the pattern of these fluctuations. The photoperiodic influences do not seem to be mediated by the pineal organ.

Pineal vasotocin: release into cat cerebrospinal fluid by melanocyte-stimulating hormone release-inhibiting factor.

The intracarotid injection of both synthetic melanocyte-stimulating hormone release-inhibiting factor (MIF) and purified MIF prepared from bovine hypothalami induces arginine vasotocin release into cerebrospinal fluid of cats and significantly decreases the pineal arginine vasotocin content at 5 minutes after the injection. The present results demonstrate an extrapituitary endocrine effect of synthetic and purified bovine MIF.

Pineal Vasotocin: Release into Cat Cerebrospinal Fluid by Melanocyte-Stimulating Hormone Release-Inhibiting Factor

The intracarotid injection of both synthetic melanocyte-stimulating hormone release-inhibiting factor (MIF) and purified MIF prepared from bovine hypothalami induces arginine vasotocin release into cerebrospinal fluid of cats and significantly decreases the pineal arginine vasotocin content at 5 minutes after the injection. The present results demonstrate an extrapituitary endocrine effect of synthetic and purified bovine MIF.

Vasotocin content in the pineal gland of foetal, newborn and adult male rats.

Institute of Endocrinology, Bucharest, Rumania (Received 6 January 1975) We have reported (Pavel, 1971) that the foetal bovine pineal contains about 27 times more arginine-vasotocin (AVT) than adult pineals, as deduced from its hydro-osmotic activities, and we have suggested that pineal AVT is elaborated by secretory ependymal cells. More recently, Pavel, Dorcescu, Petrescu-Holban & Ghinea (1973) have demonstrated that pineal ependymal cells from human foetuses can synthesize an AVT-like peptide when cultured in vitro. Since it has been shown that pineal secretory ependymal cells markedly regress after birth (Palkovits, Gábor & Lukács, 1962; Anderson, 1965), we have investigated whether this regression is accompanied by a corresponding reduction in the pineal AVT content. Foetal (17–19 days post coitum), newborn (1–5 days post partum) and adult, male Wistar rats (each group comprised 30 animals) were used. The pineals, removed within 30 s of decapitation, were defatted in acetone for 24 h, homogenized

Hormonal content and ultrastructure of the disconnected neural lobe of the grass frog ( Rana pipiens)

Based on changes in ultrastructure and vasotocin content, two postoperative phases can be distinguished in the neural lobes disconnected from the hypothalamus. During the first phase (first 2 days after transection) only very few axons start to degenerate, and the vasotocin content does not differ from that of the control glands. Axons filled with tubular formations are more numerous than in the controls. The second phase (6th to 9th postoperative days) is characterized by the degeneration of most of the neurosecretory axons and by a dramatic fall in the vasotocin content of the glands. During this phase, the number of Golgi complexes in the pituicytes increases considerably. Simultaneously, the appearance of well organized canaliculi lined by pituicytes is observed. A second cell type, in addition to pituicytes, is observed in the second phase. These cells have a charteristic nucleus and a cytoplasm mainly occupied by rough endoplasmic reticulum and lipid droplets. The pituicytic reorganization and the appearance of a new type of cell indicate that the chronically disconnected neural lobe is not a dead formation but a structure that may play some unknown functional role. The capillaries of the disconnected neural lobe are characterized by the widening of the endothelial fenestrations and the disappearance of their membrane, which results in a direct communication between the capillary lumen and the perivascular space. White blood cells are densely packed against the capillary walls, and most of these cells have processes that penetrate the endothelial openings and contact the perivascular basement membrane.

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.

Release of vasotocin and oviposition in the hen.

Tanaka & Nakajo (1962) have reported a decrease in the content of vasotocin in the posterior pituitary of hens coincident with oviposition, suggesting that the hormone was released into the blood and causes oviposition. Douglas & Sturkie (1964) assayed vasotocin in the blood of laying hens and found that the concentration of the hormone increased markedly a few minutes before oviposition, returning to resting levels within 10–20 min. after laying. Little is known about the factors involved in the release of vasotocin and this is the principal objective of this study. Vasotocin was assayed on the isolated frog bladder (Rana catesbiana) by a modification of the method of Sawyer (1960). The movement of water across the bladder wall is proportional to log concentration of hormone acting upon it. Oxytocin (Pitocin assayed against synthetic oxytocin) was used as the standard. Three standard points, 2, 10 and 50 m-u. oxytocin/ml. bath solution,