Zones of Exocytotic Release on Bovine Adrenal Medullary Cells in Culture
NORTH CAROLINA UNIV AT CHAPEL HILL DEPTOF CHEMISTRY
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Exocytotic secretion of catecholamines from bovine adrenal medullary cells in culture was examined by amperometry with 1-micrometer radius carbon- fiber electrodes. Secretion is observed as a series of current spikes which originate from a single cell upon exposure to a secretagogue. The small size of the electrodes was exploited to detect and map exocytotic release sites on the surface of bovine adrenal medullary cells. The re ease sites are spatially stable on a time-scale of 15 minutes. These quantitative studies reveal for the first time that release sites are spatially localized on endocrine cells in culture. Confocal Microscopy experiments which fluorescently monitor the deposition of dopamine-beta-hydroxylase DbetaH from the vesicular membrane into the plasma membrane during exocytosis verify the existence of zones of exocytotic activity and inactivit on the surface of the cell. Measurement of coincident spikes with two adjacent eyectrodes has allowed the spatial resolution of the electrodes to be defined. Microelectrodes with radii of approximately 2.5 micrometers detect only spikes resulting from exocytotic events occurring within 2 micrometers of the projected circumference of the electrode on the surface of the cell.
- Medicine and Medical Research