Carbachol stimulation of inositol phosphate accumulation in rat submandibular gland fragments is not modified by VIP

1989 ◽  
Vol 135 (3) ◽  
pp. 263-269 ◽  
Author(s):  
O. LARSSON ◽  
B.B. FREDHOLM
Keyword(s):  
Submandibular Gland ◽  
Inositol Phosphate ◽  
Phosphate Accumulation ◽  
Inositol Phosphate Accumulation ◽  
Rat Submandibular Gland ◽  
Stimulation Of

Adrenergic stimulation of inositol phosphate accumulation in tracheal epithelium

1989 ◽  
Vol 66 (1) ◽  
pp. 504-508 ◽  
Author(s):  
T. Bainbridge ◽  
R. D. Feldman ◽  
M. J. Welsh
Keyword(s):  
Adrenergic Receptor ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Second Messengers ◽  
Receptor Activation ◽  
Adrenergic Stimulation ◽  
Cl Secretion ◽  
Phosphate Accumulation ◽  
Inositol Phosphate Accumulation ◽  
Stimulation Of

To determine whether inositol phosphates are important second messengers in the regulation of Cl- secretion by airway epithelia, we examined the relationship between inositol phosphate accumulation and Cl- secretion in response to adrenergic agonists. We found that epinephrine stimulated Cl- secretion and inositol phosphate accumulation with similar concentration dependence. Although isoproterenol stimulated Cl- secretion, there was no effect of beta-adrenergic receptor activation on inositol phosphate accumulation. In contrast, alpha 1-adrenergic receptor activation stimulated inositol phosphate accumulation but failed to induce Cl- secretion. Another Cl- secretagogue, prostaglandin E1, also failed to stimulate inositol phosphate accumulation. These data suggest that inositol phosphate accumulation is neither sufficient nor required for stimulation of Cl- secretion in cultured canine tracheal epithelial cells.

scholarly journals Exposure of cultured hepatocytes to cyclic AMP enhances the vasopressin-mediated stimulation of inositol phosphate production

1989 ◽  
Vol 257 (2) ◽  
pp. 455-460 ◽  
Author(s):  
R A Pittner ◽  
J N Fain
Keyword(s):  
Cyclic Amp ◽  
Inositol Phosphate ◽  
Rat Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
Phosphate Accumulation ◽  
Primary Monolayer Culture ◽  
Inositol Phosphate Production ◽  
Inositol Phosphate Accumulation ◽  
Primary Monolayer ◽  
Stimulation Of

Isolated rat hepatocytes in primary monolayer culture were maintained for 18-24 h in the presence of 10% (v/v) serum and [3H]inositol. Vasopressin (100 nM) stimulated the production of inositol mono-, bis- and tris-phosphates (IP1, IP2, and IP3). Prior exposure of hepatocytes to 8-bromo cyclic AMP (8Br-cAMP; 100 microM), but not 8-bromo cyclic GMP, enhanced the vasopressin-mediated stimulation of inositol phosphate accumulation, but had no significant effect on their formation in the absence of vasopressin. The effect of the cyclic AMP analogue was mimicked by glucagon (10 nM), and was seen whether cyclic AMP or glucagon was added 5 min or 12 h before the addition of vasopressin. An 8 h incubation with dexamethasone (100 nM) enhanced the accumulation of IP3, but not that of IP2 or IP1, in the presence of 8Br-cAMP and vasopressin. Cycloheximide or actinomycin D had little effect on the vasopressin stimulation of inositol phosphate accumulation, after an 8 h incubation in the presence or absence of 8Br-cAMP.

G protein in stimulation of PI hydrolysis by CCK in isolated rat pancreatic acinar cells

1988 ◽  
Vol 255 (5) ◽  
pp. E652-E659 ◽  
Author(s):  
T. Matozaki ◽  
C. Sakamoto ◽  
M. Nagao ◽  
H. Nishizaki ◽  
S. Baba
Keyword(s):  
G Protein ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Secretory Rate ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Phosphate Accumulation ◽  
Maximal Stimulation ◽  
Inositol Phosphate Accumulation ◽  
Stimulation Of

To clarify the possible role of a guanine nucleotide-binding protein (G protein) in the signal transducing system activated by cholecystokinin (CCK), actions of CCK on rat pancreatic acini were compared with those of fluoride, a well-known activator of stimulatory (Gs) or inhibitory (Gi) G protein. When acini were incubated with increasing concentrations of either CCK-octapeptide (CCK8) or NaF, a maximal stimulation of amylase release from acini occurred at 100 pM CCK8 or 10 mM NaF, respectively; this secretory rate decreased as CCK8 or NaF concentration was increased. NaF caused an increased in cytoplasmic Ca2+ concentration from the internal Ca2+ store and stimulated accumulation of inositol phosphates in acini, as observed with CCK. However, NaF-stimulated Ca2+ mobilization had a lag period before detectable stimulation and was potentiated by AlCl3. These stimulatory effects of NaF appeared to be independent of cellular adenosine 3',5'-cyclic monophosphate (cAMP). Pretreatment with cholera toxin or pertussis toxin did not affect CCK8- or NaF-induced inositol phosphate accumulation or Ca2+ mobilization. 5'-Guanylimidodiphosphate activated the generation of inositol phosphates in the [3H]inositol-labeled pancreatic acinar cell membrane preparation, with half-maximal and maximal stimulation at 1 and 10 microM, respectively. Furthermore, the effects of submaximal CCK concentrations on inositol phosphate accumulation in membranes were markedly potentiated in the presence of 100 microM GTP, which alone was ineffective. Combined findings of the present study strongly suggest that pancreatic CCK receptors are probably coupled to the activation of polyphosphoinositide (PI) breakdown by a G protein, which appears to be fluoride sensitive but is other than Gs- or Gi-like protein.

scholarly journals A Miniaturized Column Chromatography Method for Measuring Receptor-Mediated Inositol Phosphate Accumulation

2004 ◽  
Vol 9 (4) ◽  
pp. 343-353 ◽  
Author(s):  
Elfrida R. Benjamin ◽  
Sarah L. Haftl ◽  
Dimitris N. Xanthos ◽  
Gregg Crumley ◽  
Mohamed Hachicha ◽  
...  
Keyword(s):  
Anion Exchange ◽  
Column Chromatography ◽  
Large Volume ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Assay Method ◽  
Signal To Noise ◽  
Chromatography Method ◽  
Phosphate Accumulation ◽  
Inositol Phosphate Accumulation

Inositol phosphates (IPs), such as 1,4,5-inositol-trisphosphate (IP3), comprise a ubiquitous intracellular signaling cascade initiated in response to G protein-coupled receptor-mediated activation of phospholipase C. Classical methods for measuring intracellular accumulation of these molecules include time-consuming high-performance liquid chromatography (HPLC) separation or large-volume, gravity-fed anion-exchange column chromatography. More recent approaches, such as radio-receptor and AlphaScreen™ assays, offer higher throughput. However, these techniques rely on measurement of IP3 itself, rather than its accumulation with other downstream IPs, and often suffer from poor signal-to-noise ratios due to the transient nature of IP3. The authors have developed a miniaturized, anion-exchange chromatography method for measuring inositol phosphate accumulation in cells that takes advantage of signal amplification achieved through measuring IP3 and downstream IPs. This assay uses centrifugation of 96-well-formatted anion-exchange mini-columns for the isolation of radiolabeled inositol phosphates from cell extracts, followed by low-background dry-scintillation counting. This improved assay method measures receptor-mediated IP accumulation with signal-to-noise and pharmacological values comparable to the classical large-volume, column-based methods. Assay validation data for recombinant muscarinic receptor 1, galanin receptor 2, and rat astrocyte metabotropic glutamate receptor 5 are presented. This miniaturized protocol reduces reagent usage and assay time as compared to large-column methods and is compatible with standard 96-well scintillation counters.

scholarly journals Beryllium competitively inhibits brain myo-inositol monophosphatase, but unlike lithium does not enhance agonist-induced inositol phosphate accumulation

1993 ◽  
Vol 291 (2) ◽  
pp. 369-374 ◽  
Author(s):  
W S Faraci ◽  
S H Zorn ◽  
A V Bakker ◽  
E Jackson ◽  
K Pratt
Keyword(s):  
Rat Brain ◽  
Inositol Phosphate ◽  
Bipolar Depression ◽  
Neuroblastoma Cell ◽  
Brain Slices ◽  
Human Neuroblastoma Cell ◽  
Inositol Monophosphatase ◽  
Human Neuroblastoma ◽  
Phosphate Accumulation ◽  
Inositol Phosphate Accumulation

Despite limiting side-effects, lithium is the drug of choice for the treatment of bipolar depression. Its action may be due, in part, to its ability to dampen phosphatidylinositol turnover by inhibiting myo-inositol monophosphatase. Beryllium has been identified as a potent inhibitor of partially purified myo-inositol monophosphatase isolated from rat brain (Ki = 150 nM), bovine brain (Ki = 35 nM), and from the human neuroblastoma cell line SK-N-SH (Ki = 85 nM). It is over three orders of magnitude more potent than LiCl (Ki = 0.5-1.2 mM). Kinetic analysis reveals that beryllium is a competitive inhibitor of myo-inositol monophosphatase, in contrast with lithium which is an uncompetitive inhibitor. Inhibition of exogenous [3H]inositol phosphate hydrolysis by beryllium (IC50 = 250-300 nM) was observed to the same maximal extent as that seen with lithium in permeabilized SK-N-SH cells, reflecting inhibition of cellular myo-inositol monophosphatase. However, in contrast with that observed with lithium, agonist-induced accumulation of inositol phosphate was not observed with beryllium in permeabilized and non-permeabilized SK-N-SH cells and in rat brain slices. Similar results were obtained in permeabilized SK-N-SH cells when GTP-gamma-S was used as an alternative stimulator of inositol phosphate accumulation. The disparity in the actions of beryllium and lithium suggest that either (1) selective inhibition of myo-inositol monophosphatase does not completely explain the action of lithium on the phosphatidylinositol cycle, or (2) that uncompetitive inhibition of myo-inositol monophosphatase is a necessary requirement to observe functional lithium mimetic activity.

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