Serotonin secretion by human carcinoid BON cells.
BON cells are human carcinoid cells that secrete serotonin (5-HT) and various peptides. Secretion of [(3)H]5-HT by cell cultures was investigated. Acetylcholine (Ach) stimulated secretion through a somatostatin-sensitive muscarinic pathway, whereas isoproterenol was inefficient. [(3)H]5-HT secretion also was induced by Ca(2+) in the presence of the ionophore A-23187 or after digitonin permeabilization. These two processes were insensitive to stomatostatin. Ba(2+) induced an efficient somatostatin-sensitive [(3)H]5-HT secretory response. Secretion also was analyzed at the single-cell level, using carbon fiber amperometry and evanescent-field fluorescence microscopy, after labeling the secretory vesicles by transfection of the cells with a NPY-GFP construct. Both techniques revealed slow kinetics of secretory responses, suggesting that ready-to-fuse vesicles do not accumulate in these cells. Single secretory vesicles were imaged either in resting conditions or after addition of Ca(2+) ions to digitonin-permeabilized cells. The three-dimensional movements of the vesicles before exocytosis were analyzed. The mean velocity of vesicles that released their content was lower than that of silent ones. Even in the case of mobile vesicles, exocytosis often was preceded by a period of arrest lasting at least 15 seconds, consistent with a docking/priming step.
Tran
Viet Samuel
VS
Biologie moléculaire et cellulaire de la secretion, CNRS UPR 1929, Institut de Biologie Physico-Chimique, 75005 Paris, France.
Marion-Audibert
Anne-Marie
AM
Karatekin
Erdem
E
Huet
Sebastien
S
Cribier
Sophie
S
Guillaumie
Koulm
K
Chapuis
Catherine
C
Desnos
Claire
C
Darchen
François
F
Henry
Jean-Pierre
JP
D002276:Carcinoid Tumor; D045744:Cell Line, Tumor / Q000378:metabolism; D004759:Enterochromaffin Cells / Q000378:metabolism*; D006801:Humans; D010190:Pancreatic Neoplasms; D012701:Serotonin / Q000378:metabolism*
D012701:Serotonin