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Results for “PITUITARY GLAND, POSTERIOR”

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At least 145 records · Page 8Linked to original sources

PubMed1994

PACAP-27 and PACAP-38: vascular effects in the eye and some other tissues in the rabbit.

The effects of pituitary adenylate cyclase activating polypeptide (PACAP) on regional blood flow in the eye and other tissues were investigated in albino rabbits. Direct determination of the flow from a cannulated vortex vein, in animals pretreated with a vasopressin receptor antagonist, showed that i.v. infusion of either PACAP-27 or PACAP-38 caused a dose-dependent (0.08-0.64 pmol/kg per min) decrease in the uveal vascular resistance. Regional blood flow was determined, with radioactive microspheres, during i.v. infusion of PACAP-27 or PACAP-38 (0.64 pmol/kg per min) in rabbits pretreated with hexamethonium and a vasopressin receptor antagonist. In these experiments, both PACAP-27 and PACAP-38 increased choroidal blood flow by about 50%, whereas there was no effect in the anterior uvea. Nor was there any major effect on blood flow in the anterior uvea after intracameral injection of PACAP-27 or PACAP-38 (3 pmol). The largest blood flow increases, caused by i.v. infusion of PACAP-27 or PACAP-38, were observed in the parotid gland, submandibular gland, eyelids and nictitating membrane. Local blood flow in the choroid plexus, pineal gland, posterior pituitary gland, stomach, kidney and adrenal gland was also significantly increased during the i.v. infusion of PACAP-27. The results of the present investigation indicate that PACAP-27 and PACAP-38 are about 100 times more potent than vasoactive intestinal polypeptide and peptide histidine isoleucine as vasodilators in the rabbit choroid and, possibly, also in many other tissues of the rabbit.

Animals↗

PubMed1991

Binding sites for atrial natriuretic peptide (ANP) on cultured pituicytes: lack of effect of ANP on release of neurohypophysial hormones in vitro.

Receptors for atrial natriuretic peptide (ANP) are known to be present in the posterior pituitary gland and this is a possible site of action of ANP to modulate neurohypophysial hormone release. Pituicytes cultured from adult rat neurohypophyses are shown to possess high affinity binding sites for ANP, suggesting that in vivo a population of neurohypophysial ANP receptors are present on these astrocytic glial cells. alpha-rANP (1-100 nM) did not modulate the basal or electrically stimulated release of oxytocin or vasopressin from the isolated neurohypophysis in vitro. The physiological significance of the glial ANP binding sites thus remains unknown.

Animals↗

PubMed1983

High-protein carboxymethylase activity and low endogenous methyl acceptor proteins in posterior pituitary lobe of rats lacking neurophysin-vasopressin (Brattleboro rats).

The activity of protein carboxymethylase and the endogenous protein methyl acceptor capacity were examined in the posterior, intermediate, and anterior lobes of the pituitaries of homozygous Brattleboro rats with diabetes insipidus and in heterozygous Brattleboro and Long-Evans control rats. Protein carboxyl methylation is selectively altered in the posterior pituitary lobes of homozygous Brattleboro rats. Protein carboxymethylase activity is higher (+40%) and endogenous methyl acceptor protein capacity is lower (-80%) with respect to heterozygous Brattleboro and Long-Evans control rats. This latter change is correlated with decreased methylation of proteins of a molecular weight of approximately 11K daltons, is selective for the posterior pituitary lobe, since it does not occur in the intermediate and anterior lobes, and probably reflects the absence of vasopressin-associated neurophysin in homozygous Brattleboro rats. Our results support a physiological role of protein carboxyl methylation in the neurosecretory process in the posterior pituitary gland.

Animals↗

PubMed1975

Isolation and some observations of the properties of a bovine neurohypophysial milk-ejecting factor.

A substance possessing milk-ejecting activity has been isolated from an acetone powder preparation of bovine posterior pituitary glands by Sephadex G-25 chromatography of the neurophysin-neurohypophysial hormone complex. While the material possessed an oxytocic activity of 2.8 IU/mg as measured on the isolated rat uterus, the milk-ejecting activity was more than three fold greater, 9.6 IU/mg. The peptide had an antidiuretic activity of 0.133 IU/mg and a pressor activity of 0.083 IU/mg. Neither the uterine-stimulating action nor the pressor activity was destroyed by incubating the peptide with 0.01 M sodium thioglycollate at 65 degrees C for 5 min. The oxytocic activity was antagonized neither by 1.4 X 10(-6) M atropine nor 3.3 X 10(-7) M phenoxybenzamine.

Amino Acids↗

PubMed1986

[Phylogeny of neurohypophyseal hormones in birds: microidentification of mesotocin and vasotocin in the ostrich (Struthio camelus)].

Ostrich (Struthio camelus) neurohypophysial hormones have been isolated from 5 freeze-dried posterior pituitary glands. Purification has involved three steps: a first molecular sieving on Sephadex G-75 for eliminating proteins, a second molecular sieving on Bio-Gel P4 for separating the two active principles and a high pressure reverse-phase liquid chromatography (HPLC) on Nova-Pak C 18 with an 10 mM acetate-acetonitrile gradient for isolating each hormone. The active peptides have been identified by their retention time in HPLC and their amino acid composition. Mesotocin and vasotocin have thus been characterized. Although the phylogeny of Ratites is disputed, in particular their possible common origin with Carinates, which include most of the living birds, species of the first sub-class seem to have the same neurohypophysial hormones as those of the second.

Animals↗

PubMed1980