Novel action of pituitary adenylate cyclase-activating polypeptide. Stimulation of extracellular acidification in rat pituitary GH4C1 cells.
Pituitary adenylate cyclase-activating polypeptide (PACAP) is a member of the vasoactive intestinal peptide/secretin family. Using microphysiometry, we have found that PACAP acutely (1 min) increased the extracellular acidification rate (ECAR) in GH4C1 cells approximately 40% above basal in a concentration-dependent manner. ECAR, maximally induced by PACAP, can be increased further by thyrotropin-releasing hormone (TRH), indicating that the signalling pathways for these two neuropeptides are not identical. In studies on the mechanism of PACAP-enhanced ECAR, we found that maximum stimulation of the cAMP/PKA pathway by treatment with FSK, or the PKC pathway with PMA, did not inhibit the ECAR response to PACAP. The PKC inhibitor calphostin C and the MAP kinase inhibitor PD98059 had no effect on the ECAR response to PACAP. Furthermore, PACAP induced little or no change in cytosolic Ca(2+) ([Ca(2+)](i)), while TRH induced a large increase in [Ca(2+)](i). However, the tyrosine kinase inhibitor genistein completely blocked PACAP-induced ECAR, suggesting involvement of tyrosine kinase(s). We conclude that PACAP causes an increase in ECAR in GH4C1 rat pituitary cells, which is not dependent on the PKA, PKC, MAP kinase or Ca(2+) signalling pathways, but does require tyrosine kinase activity.
Chen
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Department of Cancer Cell Biology, Harvard School of Public Health, Harvard Medical School, Boston, MA 02115, USA.
Tang
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Tashjian
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D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000502:physiology; D005419:Flavonoids / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology; D009479:Neuropeptides / Q000494:pharmacology*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D010902:Pituitary Gland / Q000166:cytology / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
C495403:Adcyap1 protein, rat; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009281:Naphthalenes; D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D005576:Colforsin; D013973:Thyrotropin-Releasing Hormone; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium