Secretion of Catecholamines from Individual Adrenal Medullary Chromaffin Cells

Abstract

Catecholamine secretion has been measured with electrochemical techniques from isolated, single adrenal medullary chromaffin cells with carbon-fiber microelectrodes. The electrode tip, which is of similar dimensions to the cell, is placed adjacent to the cell to enable the measurement of local secretion. Secretion is caused by exposing the cell to nanoliter volumes of solution containing nicotinic receptor agonists or depolarizing agents. The identification of secreted substances is made with cyclic voltammetry at both bare electrodes and electrodes coated with a perfluorinated cation-exchange polymer. Catecholamine secretion is induced by nicotine (10-500 microM), carbamylcholine (1 mM), and K+ (60 mM). All agents that induce secretion lead to a broad envelope of secreted catecholamines on which sharp concentration spikes are superimposed. The concentration spikes can be monitored with a time resolution of tens of milliseconds when the electrodes are used in the amperometric mode. Release induced by nicotine and K+ is inhibited by Cd2+ (0.5 mM), and hexamethonium selectively blocks the nicotine-induced secretion. The actions of nicotine are found to continue for a longer period of time than those of the other secretagogues tested.

Insulin-like growth factor II signaling through the insulin-like growth factor II/mannose-6-phosphate receptor promotes exocytosis in insulin-secreting cells

“…IGF-II also The spikes elicited are of similar size and time course for the two stimulation protocols. This is expected for an exocytosis measurement because the amount released per vesicle and the amount detected in a spike will be independent of the method used to initiate exocytosis (30,31). In both cases, the spikes are superimposed over a broad envelope, although the envelope is more obvious with IGF-II stimulation.…”

“…In both cases, the spikes are superimposed over a broad envelope, although the envelope is more obvious with IGF-II stimulation. The envelope is partially due to overlapping of many spikes occurring simultaneously (30,31) and partially due to a background change associated with the IGF-II stimulation. The bottom trace shows the background shift induced by IGF-II addition and recorded in a ␤ cell not responding to the agonist.…”

“…3B). In previous studies, this method has been used to detect exocytosis from adrenal chromaffin cells, PC-12 cells, mast cells, and individual pancreatic ␤ cells (23,(30)(31)(32)(33)(34). The anodic current resulting from a secreted substance appears as a series of spikes that indicate concentration pulses occurring at the electrode surface.…”

Dynamin I plays dual roles in the activity-dependent shift in exocytic mode in mouse adrenal chromaffin cells

“…Additionally, previous work using single-cell carbon fiber amperometry [30,31] has indicated that quantal size positively depends on cell Ca 2+ levels [32] by transitioning from Ω-form fusion transients to 'full collapse' events, thus expelling all granule contents [3,8,9]. We measured the quantal size of catecholamine secretion in Dyn transfected cells compared to untransfected controls to determine the relative occurrence of Ω-form 'kiss an run' to 'full collapse'.…”

ω‐agatoxin IVA blocks nicotinic receptor channels in bovine chromaffin cells

“…Adrenomedullary chromaffin cells secrete catecholamines in response to nicotinic cholinergic agonists [1][2][3]. Following activation of the nicotinic receptor, a non-selective cation channel, associated to the receptor, opens [4,5], and the membrane of chromaffin cells is depolarized [6][7][8].…”