Contrasting effects of PACAP and carbachol on [Ca2+]i and inositol phosphates in human neuroblastoma NB-OK-1 cells.
The effects of PACAPs on [Ca2+]i were compared to those of carbachol in human neuroblastoma NB-OK-1 cells. PACAP(1-27) and PACAP(1-38) increased [Ca2+]i in a biphasic manner: a transient rise and a secondary plateau. The transient phase reflected the mobilization of [Ca2+]i pool(s) via the inositol phosphate pathway. The modest sustained plateau required extracellular Ca2+. Carbachol also increased [Ca2+]i in a biphasic manner, but it mobilized intracellular Ca2+ pool(s) with a higher efficacy than PACAPs, then greatly increased Ca2+ entry, this being accompanied by a more marked and prolonged elevation of IP3 and IP4 than with PACAPs. It is likely that cAMP-mediated phosphorylations due to PACAPs facilitated desensitization at the PACAP receptor-phospholipase C level, so that there was less Ca2+ handling through PACAP receptors than with muscarinic M1 receptors.
Delporte
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Department of Biochemistry and Nutrition, Medical School, Université Libre de Bruxelles, Belgium.
Van Praet
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Herchuelz
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Winand
J
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Christophe
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D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D005576:Colforsin / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism*; D009447:Neuroblastoma; D009474:Neurons / Q000187:drug effects*; D009479:Neuropeptides / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011188:Potassium / Q000494:pharmacology; D014407:Tumor Cells, Cultured
C495401:ADCYAP1 protein, human; D007295:Inositol Phosphates; D009479:Neuropeptides; D010446:Peptide Fragments; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; C075647:pituitary adenylate-cyclase-activating-peptide (6-38); D005576:Colforsin; D004533:Egtazic Acid; D002217:Carbachol; D011188:Potassium; D002118:Calcium