Slow spontaneous secretion from single large dense-core vesicles monitored in neuroendocrine cells.
Hormones are released from cells by passing through an exocytotic pore that forms after vesicle and plasma membrane fusion. In stimulated exocytosis vesicle content is discharged swiftly. Although rapid vesicle discharge has also been proposed to mediate basal secretion, this has not been studied directly. We investigated basal hormone release by preloading fluorescent peptides into single vesicles. The hormone discharge, monitored with confocal microscopy, was compared with the simultaneous loading of vesicle by FM styryl dye. In stimulated vesicles FM 4-64 (4 microM), loading and hormone discharge occurs within seconds. In contrast, in approximately 50% of spontaneously releasing vesicles, the vesicle content discharge and the FM 4-64 loading were slow (approximately 3 min). These results show that in peptide secreting neuroendocrine cells the elementary vesicle content discharge differs in basal and in stimulated exocytosis. It is proposed that the view dating back for some decades, which is that, at rest, the vesicle discharge of hormones and neurotransmitters is similar to that occurring after stimulation, needs to be extended. In addition to the classical paradigm that secretory capacity of a cell is determined by controlling the probability of occurrence of elementary exocytotic events, one will have to consider activity modulation of elementary exocytotic events as well.
Stenovec
Matjaz
M
Celica Biomedical Sciences Center, Ljubljana, Slovenia.
Kreft
Marko
M
Poberaj
Igor
I
Betz
William J
WJ
Zorec
Robert
R
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D004058:Diffusion; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D005456:Fluorescent Dyes; D008297:Male; D008561:Membrane Fusion; D018613:Microscopy, Confocal; D008954:Models, Biological; D018408:Patch-Clamp Techniques; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012636:Secretory Rate; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism*; D014162:Transfection
D005456:Fluorescent Dyes; D011189:Potassium Chloride; D009320:Atrial Natriuretic Factor; D011388:Prolactin