Abstract
Thyroid parafollicular (PF) cells are neural crest-derived endocrine cells that secrete serotonin and calcitonin. The secretory vesicles of PF cells acidify when secretion is induced by increased extracellular Ca2+ or TSH. We tested the hypothesis that acidification is regulated by secretogogue-gated Cl- channels in vesicular membranes. Cl- channel (p64) immunoreactivity was enriched in purified PF vesicles. X-Ray microanalysis showed a change in chlorine level in PF vesicles in response to secretogogue-stimulation of isolated cells. Secretogogue stimulation also altered the degree of p64 channel phosphorylation. Protein kinase and phosphatase inhibitors antagonized secretogogue-induced vesicle acidification and secretion; however, secretion could occur even when acidification was blocked. We conclude that acidification of PF vesicles is regulated by a gatable Cl- channel in vesicle membranes and that protein phosphorylation and dephosphorylation are involved in channel activation. Acidification of vesicles is not required for exocytosis.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Acridine Orange
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Alkaloids / pharmacology
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Animals
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Barium / pharmacology
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Calcium / pharmacology*
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Calmodulin / antagonists & inhibitors
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Chloride Channels / analysis
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Chloride Channels / drug effects
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Chloride Channels / physiology*
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Chlorides / analysis
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Cyclosporine / pharmacology
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Electron Probe Microanalysis
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Ethers, Cyclic / pharmacology
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Immunoblotting
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Immunohistochemistry
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Intracellular Membranes / chemistry
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Intracellular Membranes / physiology*
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Intracellular Membranes / ultrastructure
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Ion Channel Gating / drug effects
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Ion Channel Gating / physiology*
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Okadaic Acid
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Phorbol Esters / pharmacology
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Phosphoric Monoester Hydrolases / antagonists & inhibitors
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Phosphorylation
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Precipitin Tests
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Protein Kinase Inhibitors
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Serotonin / metabolism
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Sheep
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Staurosporine
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Tacrolimus / pharmacology
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Thyroid Gland / cytology*
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Thyroid Gland / physiology
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Thyroid Gland / ultrastructure
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Thyrotropin / pharmacology*
Substances
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Alkaloids
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Calmodulin
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Chloride Channels
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Chlorides
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Ethers, Cyclic
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Phorbol Esters
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Protein Kinase Inhibitors
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Okadaic Acid
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Barium
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Serotonin
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Cyclosporine
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Thyrotropin
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Phosphoric Monoester Hydrolases
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Acridine Orange
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Staurosporine
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Calcium
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Tacrolimus