Dopamine does not attenuate phosphoinositide hydrolysis in rat anterior pituitary cells

1986 ◽  
Vol 110 (3) ◽  
pp. 389-393 ◽  
Author(s):  
P. L. Canonico ◽  
W. D. Jarvis ◽  
A. M. Judd ◽  
R. M. MacLeod
Keyword(s):  
Anterior Pituitary ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Pituitary Cells ◽  
Anterior Pituitary Cells ◽  
Marked Diminution ◽  
Inositol Phosphate Production ◽  
Concomitant Reduction ◽  
Potent Agonist ◽  
Hydrolysis Of

ABSTRACT The hydrolysis of membrane phosphatidylinositol to yield [3H]labelled inositol phosphates by anterior pituitary cells was stimulated significantly by angiotensin II, TRH and neurotensin over a broad range of concentrations. These secretagogues also stimulated release of prolactin. Although the coincident incubation of dopamine with these agents resulted in a marked diminution of prolactin release, no concomitant reduction in inositol phosphate production was observed. In addition, bromocriptine, a potent agonist of dopamine, also proved ineffective in blunting stimulated phosphatidylinositol catabolism. Although it slightly inhibited basal rates of inositol tris-, bis- and monophosphate production, these results show that the secretagogue-mediated enhancement of phosphatidylinositol catabolism may be correlated with an increased release of prolactin and that the inhibition of hormone release produced by dopamine is not achieved by reducing basal or secretagogue-mediated inositol phosphate production. J. Endocr. (1986) 110, 389–393

Maitotoxin increases inositol phosphates in rat anterior pituitary cells

1991 ◽  
Vol 6 (1) ◽  
pp. 95-99 ◽  
Author(s):  
M. A. Sortino ◽  
T. M. Delahunty ◽  
T. Yasumoto ◽  
M. J. Cronin
Keyword(s):  
Anterior Pituitary ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Cell Types ◽  
Calcium Stores ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Anterior Pituitary Cells ◽  
Intracellular Ca

ABSTRACT Maitotoxin is a potent marine poison that mobilizes calcium in most vertebrate cell types and accelerates secretion from anterior pituitary cells. It is not known whether voltage-sensitive calcium channels or other mechanisms initiate the effects of maitotoxin on anterior pituitary cells. Changes in intracellular Ca2+ levels may also be achieved by releasing internal calcium stores via inositol trisphosphate (InsP3). Indeed, maitotoxin rapidly increased inositol phosphate accumulation in a concentration-dependent manner. Calcium channel antagonists such as nifedipine and verapamil did not block this response nor did calcium-mobilizing agents (BAYk8644, A23187) mimic this effect. These data suggest that the mechanism by which maitotoxin acts at the pituitary may include the activation of an enzyme that produces the calcium-mobilizing signal InsP3.

Cholinergic Stimulation of Inositol Phosphate Production in Cultured Anterior Pituitary Cells

1987 ◽  
Vol 46 (4) ◽  
pp. 306-311 ◽  
Author(s):  
P. Luigi Canonico ◽  
David Jarvis ◽  
Maria Angela Sortino ◽  
Umberto Scapagnini ◽  
Robert M. MacLeod
Keyword(s):  
Anterior Pituitary ◽  
Inositol Phosphate ◽  
Pituitary Cells ◽  
Cholinergic Stimulation ◽  
Anterior Pituitary Cells ◽  
Inositol Phosphate Production ◽  
Stimulation Of

Kallidin-induced stimulation of inositol phosphate production and prolactin release in rat anterior pituitary cells

1990 ◽  
Vol 123 (1) ◽  
pp. 37-42 ◽  
Author(s):  
T. Hugh Jones ◽  
Barry L. Brown ◽  
Pauline R. M. Dobson
Keyword(s):  
Anterior Pituitary ◽  
Inositol Phosphate ◽  
Prolactin Secretion ◽  
Male Rat ◽  
Pituitary Cells ◽  
Phosphoinositide Metabolism ◽  
Prolactin Release ◽  
Anterior Pituitary Cells ◽  
Inositol Phosphate Production ◽  
Stimulation Of

Abstract. The effect of the kinin, kallidin (lysyl-brady-kinin) on phosphoinositide metabolism and prolactin secretion was examined in male rat anterior pituitary cells in primary culture. Kallidin was found to stimulate both total inositol phosphate production and prolactin release. The stimulation of inositol phosphate was biphasic in nature, similar to that previously reported for bradykinin, although kallidin was approximately 10-fold more potent. Kallidin also stimulated prolactin secretion provoking a maximal stimulation of 193.0±11.1 (sem)% at 1 μmol/l. These findings suggest that kallidin-induced prolactin secretion may be mediated intracellularly by activation of phosphoinositide metabolism. The B2 receptor antagonists had no significant inhibitory effects on kallidin-stimulated phosphoinositide metabolism or prolactin release. The B1 agonist des-Arg9-bradykinin has previously been shown to have no effect on either parameter. As the effects of kinins on anterior pituitary cells do not appear to be mediated by either of the known kinin receptors, they may, therefore, act via a hitherto unrecognised kinin receptor.

Specific oxytocin agonist stimulates prolactin release but has no effect on inositol phosphate accumulation in isolated rat anterior pituitary cells

1993 ◽  
Vol 10 (2) ◽  
pp. 107-114 ◽  
Author(s):  
S E Chadio ◽  
F A Antoni
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Pituitary Cells ◽  
Uterine Tissue ◽  
Prolactin Release ◽  
Anterior Pituitary Cells ◽  
Oxytocin Receptors ◽  
Stimulation Of

ABSTRACT We have previously characterized specific oxytocin receptors in the rat anterior pituitary gland, using a highly selective oxytocin receptor antagonist as radio-ligand. The aim of the present study was to examine whether occupation of these receptors by oxytocin produces a stimulation of prolactin release and a rise in the accumulation of total inositol phosphates in the rat adenohypophysis. Anterior pituitary cells harvested from randomly cycling and diethylstilboestrol (100 μg s.c.)-treated rats were perifused with Dulbecco's minimal essential medium at a rate of 0·3 ml/min. Oxytocin and the specific oxytocin agonist [Thr4-Gly7]-oxytocin (TG-OT) both stimulated a significant prolactin release at concentrations of 10-6 and 10-7 m. Oestrogen treatment did not affect the response to oxytocin, indicating that there is no straightforward correlation between receptor number and prolactin secretory response in the rat pituitary gland. The involvement of phosphoinositide hydrolysis was investigated in dispersed anterior pituitary cells and uterine tissue from randomly cycling rats. Oxytocin and arginine-vasopressin stimulated a significant (P<0·05) and dose-related increase in total inositol phosphates, vasopressin being more potent. The specific oxytocin agonist TG-OT had no effect on total inositol phosphate production in pituitary cells, but when tested in uterine tissue it significantly (P< 0.05) stimulated the accumulation of total inositol phosphate at all concentrations tested (10-5 to 10-9 m). In conclusion, the data show that oxytocin has prolactin-releasing activity, acting on specific receptors in the anterior pituitary gland. Furthermore, although oxytocin receptors in the rat uterus are coupled to the inositol phospholipid cycle, it would appear that this is not a prerequisite for the stimulation of prolactin secretion when specific oxytocin receptors in the rat adenohypophysis are activated.

Substance P stimulation of polyphosphoinositide hydrolysis in rat anterior pituitary membranes involves a GTP-dependent mechanism

1991 ◽  
Vol 130 (1) ◽  
pp. 63-70 ◽  
Author(s):  
S. E. Mau ◽  
T. Saermark
Keyword(s):  
Substance P ◽  
Pertussis Toxin ◽  
Anterior Pituitary ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Sodium Deoxycholate ◽  
Pituitary Cells ◽  
Guanine Nucleotide ◽  
Nk1 Receptor ◽  
Gtp Binding

ABSTRACT Substance P (SP) stimulates polyphosphoinositide breakdown in the rat anterior pituitary through an NK-1 receptor. In the present study we present evidence that the coupling between the SP–NK1 receptor complex and polyphosphoinositide-specific phospholipase C (PI-PLC) in rat anterior pituitary membranes may involve a mechanism consistent with a GTP-binding protein. The formation of inositol phosphates from [3H]myo-inositol-labelled anterior pituitary membranes induced by SP was potentiated by GTP and non-hydrolysable guanine nucleotides. The stimulatory effects of SP alone and SP plus GTP could be blocked by addition of GDP-β-S (guanosine 5-O-(thiodiphosphate)) in excess. Basal and SP plus guanine nucleotide-induced inositol phosphate formation were stimulated by fluoride, whereas the effect of SP alone was inhibited. Pretreatment of anterior pituitary membranes with sodium deoxycholate attenuated the inositol phosphate response elicited by GTP and GTP-γ-S, whereas basal and SP-stimulated inositol phosphate production showed a peak at 1 mg sodium deoxycholate/ml. SP, fluoride and guanine nucleotide stimulatory effects on hydrolysis of polyphosphoinositide (PPI) were unaffected by pretreatment of anterior pituitary cells with cholera or pertussis toxin for 12 h. Treatment of anterior pituitary membranes with cholera and pertussis toxin yielded [32P]ADP-ribosylation of two proteins with molecular masses of 45 and 41 kDa respectively. We conclude that SP coupling to PI-PLC through the NK1 receptor in the rat anterior pituitary involves a GTP-binding mechanism distinct from the G-proteins associated with adenylate cyclase, Gs and Gi. Journal of Endocrinology (1991) 130, 63–70

Oxytocin and vasopressin stimulate inositol phosphate production in human gestational myometrium and decidua cells

1986 ◽  
Vol 6 (7) ◽  
pp. 613-619 ◽  
Author(s):  
Michael P. Schrey ◽  
Alison M. Read ◽  
Philip J. Steer
Keyword(s):  
Arachidonic Acid ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Diacylglycerol Lipase ◽  
Inositol 1 ◽  
Inositol Phosphate Production ◽  
Acid Accumulation ◽  
Free Arachidonic Acid ◽  
Hydrolysis Of ◽  
Related Increase

The involvement of phosphoinositide hydrolysis in the action of oxytocin and vasopressin on the uterus was investigated in gestational myometrium and decidua cells by measuring the production of inositol phosphates. Both peptides stimulated a dose related increase in all three inositol phosphates in myometrium. This may be related to the control of sarcoplasmic Ca++ levels in the myometrium. Oxytocin and vasopressin also stimulated inositol 1-phosphate (IP) production in decidua cells. The hydrolysis of phosphatidylinositol by decidua homogenates exhibited a precursor-product relationship for diacylglycerol and arachidonic acid accumulation. Hence both peptides may mobilise free arachidonic acid, for prostaglandin biosynthesis, from decidua cell phosphoinositides by the sequential action of phospholipase C and diacylglycerol lipase.

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