Abstract
In this study, the secretory effects of PACAP and PACAP analogues on [3H]serotonin-loaded purified rat peritoneal mast cells (RPMCs) were investigated. PACAP(1-27) and PACAP(6-27) stimulated [3H]serotonin release with low potency (ED50: 2 x 10(-6) M) but high efficacy. The N-terminally truncated PACAP form, PACAP(6-27), stimulated tracer release with an ED50 of 0.2 x 10(-6) M, indicating a high-affinity PACAP receptor-independent mechanism of action. The secretory response to PACAP(1-27) could be inhibited by 60-min preincubation with pertussis toxin (ptx), which inhibits G proteins. U73122, a cell-permeable phospholipase C inhibitor, dose-dependently inhibited the secretory effect of 5 microM PACAP(1-27) with an IC50 value of 4 microM (N = 4; p < 0.006). We conclude that PACAP exerts a secretory effect in RPMCs by high-affinity PACAP receptor-independent direct activation of one or more G proteins, which may then activate the PLC-dependent signal-transduction pathway.
MeSH terms
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Adenylate Cyclase Toxin
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Animals
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Cell Degranulation / drug effects
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Cell Degranulation / physiology*
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Cyclic AMP / analogs & derivatives
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Cyclic AMP / pharmacology
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Estrenes / pharmacology
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GTP-Binding Proteins / physiology*
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In Vitro Techniques
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Mast Cells / drug effects
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Mast Cells / physiology*
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Neuropeptides / pharmacology*
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Peptide Fragments / pharmacology
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Peritoneal Cavity
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Pertussis Toxin
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Pituitary Adenylate Cyclase-Activating Polypeptide
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Pyrrolidinones / pharmacology
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Rats
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Rats, Inbred SHR
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Rats, Wistar
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Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
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Receptors, Pituitary Hormone / physiology*
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Sequence Deletion
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Serotonin / metabolism
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Signal Transduction
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Thionucleotides / pharmacology
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Type C Phospholipases / antagonists & inhibitors
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Virulence Factors, Bordetella / pharmacology
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p-Methoxy-N-methylphenethylamine / pharmacology
Substances
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Adcyap1 protein, rat
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Adenylate Cyclase Toxin
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Estrenes
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Neuropeptides
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Peptide Fragments
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Pituitary Adenylate Cyclase-Activating Polypeptide
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Pyrrolidinones
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Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
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Receptors, Pituitary Hormone
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Thionucleotides
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Virulence Factors, Bordetella
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pituitary adenylate-cyclase-activating peptide (6-27)
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1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
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adenosine-3',5'-cyclic phosphorothioate
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Serotonin
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p-Methoxy-N-methylphenethylamine
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Cyclic AMP
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Pertussis Toxin
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Type C Phospholipases
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GTP-Binding Proteins