scholarly journals Thyroliberin action in pituitary cells is not inhibited by pertussis toxin

1986 ◽  
Vol 237 (1) ◽  
pp. 181-186 ◽  
Author(s):  
P M Hinkle ◽  
E L Hewlett ◽  
M C Gershengorn
Keyword(s):  
Growth Hormone ◽  
Pertussis Toxin ◽  
Inositol Phosphate ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Pituitary Tumour ◽  
Pituitary Cells ◽  
Guanine Nucleotide ◽  
Muscarinic Agonists ◽  
Prolactin Synthesis

The effects of pertussis toxin on the responses of rat pituitary-tumour (GH) cells to thyrotropin-releasing hormone (thyroliberin, TRH) were examined. Treatment of cells with pertussis toxin did not alter the affinity or concentration of TRH receptors, or the sensitivity of the TRH receptor to inhibition by guanine nucleotides. TRH caused an increase in low-Km GTPase activity in membrane-containing fractions from both control and pertussis-toxin-treated cells. TRH stimulation of inositol phosphate formation was insensitive to pertussis toxin. TRH caused a biphasic increase in the concentrations of cytosolic free Ca2+ as monitored by intracellularly trapped Quin 2, and this increase was the same in control and toxin-treated cultures. The toxin did not alter the increase in prolactin and growth-hormone (somatotropin) release stimulated by TRH or shift the TRH dose-response curve, and it did not affect the TRH-induced rise in prolactin synthesis measured over 24 h. However, pertussis toxin did block the ability of somatostatin and muscarinic agonists to inhibit prolactin and growth-hormone secretion stimulated by vasoactive intestinal peptide when analysed under the same conditions as those in which the TRH system was unaffected. These data indicate that the guanine nucleotide effects on TRH binding and activity are not mediated by Ni, but possibly by another member of the family of guanine-nucleotide-dependent regulatory proteins.

Influence of catecholamines, prostaglandins and thyroid hormones on growth hormone secretion by chicken pituitary cells in vitro

1990 ◽  
Vol 7 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Dan J. Donoghue ◽  
Frank M. Perez ◽  
Bruce S.A. Diamante ◽  
Sasha Malamed ◽  
Colin G. Scanes
Keyword(s):  
Growth Hormone ◽  
Thyroid Hormones ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Pituitary Cells

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

GRF elevates cytosolic free calcium concentration in rat anterior pituitary cells

1987 ◽  
Vol 253 (5) ◽  
pp. E591-E594
Author(s):  
C. Schofl ◽  
J. Sandow ◽  
W. Knepel
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Calcium Concentration ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Free Calcium ◽  
Pituitary Cells ◽  
Maximal Increase ◽  
Anterior Pituitary Cells ◽  
Free Calcium Concentration

The effect of human growth hormone-releasing factor (GRF) on intracellular free calcium concentration ([Ca2+]i) was examined in rat anterior pituitary cells. The [Ca2+]i was monitored directly by means of the intracellularly trapped fluorescent indicator, fura-2. GRF rapidly elevated [Ca2+]i, reaching a new plateau within approximately 30 s. The half-maximally effective concentration of GRF was approximately 130 pM. GRF produced a maximal increase in [Ca2+]i by approximately 120 nM. The GRF (2 nM)-induced elevation of [Ca2+]i was abolished by removal of extracellular calcium (Ca2+ omitted, 2 mM EGTA). The GRF (2 nM)-caused rise in [Ca2+]i was largely reduced in the presence of the calcium channel blockers Mg2+ (31.2 mM) or nifedipine (1 microM). An increase in [Ca2+]i by approximately 60 nM was elicited by the addition of prostaglandin E2 (1 microM), which can stimulate growth hormone secretion independent of GRF receptors. These data indicate that GRF elevates the [Ca2+]i, possibly in somatotrophs; this GRF-induced increase in [Ca2+]i may depend on an influx of extracellular Ca2+, largely through Mg2+- and nifedipine-sensitive calcium channels.

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