scholarly journals Activin A stimulates catecholamine secretion from rat adrenal chromaffin cells: a new physiological mechanism

2005 ◽  
Vol 186 (2) ◽  
pp. R1-R5 ◽  
Author(s):  
Damien J Keating ◽  
Chen Chen
Keyword(s):  
Adrenal Cortex ◽  
Adrenal Medulla ◽  
Chromaffin Cells ◽  
Transforming Growth Factor ◽  
Activin A ◽  
Catecholamine Secretion ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Adrenal Chromaffin Cells ◽  
Adrenal Chromaffin

Activin A is a member of the transforming growth factor-β family and has known roles in the adrenal cortex, from which activin A is secreted. We aimed to find whether activin A induces secretion of catecholamines from chromaffin cells of the adrenal medulla, which neighbours the adrenal cortex in vivo. Using carbon fibre amperometry, we were able to measure catecholamine secretion in real-time from single chromaffin cells dissociated from the rat adrenal medulla. Activin A stimulated catecholamine secretion in a rapid and dose-dependent manner from chromaffin cells. This effect was fully reversible upon washout of activin A. The minimum dose at which activin A had a maximal effect was 2 nM, with an EC50 of 1.1 nM. The degree of secretion induced by activin A (2 nM) was smaller than that due to membrane depolarization caused by an increase in the external K+ concentration from 5 to 70 mM. No response to activin A was seen when Ca2+ channels were blocked by Cd2+ (200 μM). We conclude from these findings that activin A is capable of stimulating a robust level of catecholamine secretion from adrenal chromaffin cells in a concentration-dependent manner. This occurs via the opening of voltage-gated Ca2+ channels, causing Ca2+ entry, thereby triggering exocytosis. These findings illustrate a new physiological role of activin A and a new mechanism in the control of catecholamine secretion from the adrenal medulla.

scholarly journals Oxygen sensitivity in the sheep adrenal medulla: role of SK channels

2001 ◽  
Vol 281 (5) ◽  
pp. C1434-C1441 ◽  
Author(s):  
Damien J. Keating ◽  
Grigori Y. Rychkov ◽  
Michael L. Roberts
Keyword(s):  
Adrenal Medulla ◽  
Chromaffin Cells ◽  
Catecholamine Secretion ◽  
Resting Potential ◽  
Sk Channels ◽  
Adrenal Chromaffin Cells ◽  
Simultaneous Application ◽  
Adrenal Chromaffin ◽  
Small Conductance

The hypoxia-evoked secretion of catecholamines from the noninnervated fetal adrenal gland is essential for surviving intrauterine hypoxemia. The ion channels responsible for the initial depolarization that leads to catecholamine secretion have not been identified. Patch-clamp studies of adrenal chromaffin cells isolated from fetal and adult sheep revealed the presence of a Ca2+-dependent K+ current that was reduced by hypoxia. Apamin, a blocker of small-conductance K+ (SK) channels, reduced the Ca2+-dependent K+current, and the sensitivity of the channels to apamin indicated that the channels involved were of the SK2 subtype. In the presence of apamin, the hypoxia-evoked change in K+ currents was largely eliminated. Both hypoxia and apamin blocked a K+current responsible for maintaining the resting potential of the cell, and the depolarization resulting from both led to an influx of Ca2+. Simultaneous application of hypoxia and apamin did not potentiate the increase in cytosolic Ca2+ concentration beyond that seen with either agent alone. Similar results were seen with curare, another blocker of SK channels. These results indicate that closure of SK2 channels would be the initiating event in the hypoxia-evoked catecholamine secretion in the adrenal medulla.

scholarly journals Characterization of protein kinase C and its role in catecholamine secretion from bovine adrenal-medullary cells

1985 ◽  
Vol 228 (1) ◽  
pp. 35-42 ◽  
Author(s):  
K W Brocklehurst ◽  
K Morita ◽  
H B Pollard
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Chromaffin Cells ◽  
Cytosolic Fraction ◽  
Catecholamine Secretion ◽  
Dependent Manner ◽  
Adrenal Chromaffin Cells ◽  
Kinase C ◽  
Maximal Activation ◽  
Adrenal Chromaffin

Protein kinase C activity towards exogenous histone was detected in a cytosolic fraction of bovine adrenal medulla. The enzyme was dependent on Ca2+ and phosphatidylserine for its activity, with half-maximal activation being achieved at approx. 18 microM free Ca2+ and 8 micrograms of phosphatidylserine/ml. Both diolein and 4 beta-phorbol 12-myristate 13-acetate (TPA) decreased the Ca2+ requirement of the enzyme, half-maximal activation being obtained at approx. 12 microM and 9 microM free Ca2+ respectively in the presence of these agents. Many endogenous proteins in the adrenal-medullary cytosolic fraction were detected whose phosphorylation was dependent on the presence of both Ca2+ and phosphatidylserine. TPA stimulated catecholamine release from cultured bovine adrenal-chromaffin cells in a Ca2+-dependent manner. A23187 also stimulated catecholamine secretion, and at sub-optimal concentrations of TPA and A23187 a synergistic secretory response was obtained. These results are consistent with protein kinase C having a regulatory role in exocytosis in bovine adrenal chromaffin cells.

Immunogold labeling of the calcium binding protein synexin in isolated adrenal chromaffin granules and chromaffin cells

1990 ◽  
Vol 48 (3) ◽  
pp. 952-953
Author(s):  
Gemma A.J. Kuijpers ◽  
Harvey B. Pollard
Keyword(s):  
Adrenal Medulla ◽  
Calcium Binding ◽  
Chromaffin Cells ◽  
Cell Activation ◽  
Structural Information ◽  
Dependent Manner ◽  
Chromaffin Granules ◽  
Immuno Electron Microscopy ◽  
Ultrathin Sections ◽  
Adrenal Chromaffin

Exocytotic fusion of granules in the adrenal medulla chromaffin cell is triggered by a rise in the concentration of cytosolic Ca2+ upon cell activation. The protein synexin, annexin VII, was originally found in the adrenal medulla and has been shown to cause aggregation and to support fusion of chromaffin granules in a Ca2+-dependent manner. We have previously suggested that synexin may there fore play a role in the exocytotic fusion process. In order to obtain more structural information on synexin, we performed immuno-electron microscopy on frozen ultrathin sections of both isolated chromaffin granules and chromaffin cells.Chromaffin granules were isolated from bovine adrenal medulla, and synexin was isolated from bovine lung. Granules were incubated in the presence or absence of synexin (24 μg per mg granule protein) and Ca2+ (1 mM), which induces maximal granule aggregation, in 0.3M sucrose-40m MMES buffer(pH 6.0). Granules were pelleted, washed twice in buffer without synexin and fixed with 2% glutaraldehyde- 2% para formaldehyde in 0.1 M phosphate buffer (GA/PFA) for 30 min. Chromaffin cells were isolated and cultured for 3-5 days, and washed and incubated in Krebs solution with or without 20 uM nicotine. Cells were fixed 90 sec after on set of stimulation with GA/PFA for 30 min. Fixed granule or cell pellets were washed, infiltrated with 2.3 M sucrose in PBS, mounted and frozen in liquid N2.

scholarly journals Butanol Isomers Exert Distinct Effects on Voltage-Gated Calcium Channel Currents and Thus Catecholamine Secretion in Adrenal Chromaffin Cells

PLoS ONE ◽  
2014 ◽  
Vol 9 (10) ◽  
pp. e109203 ◽  
Author(s):  
Sarah McDavid ◽  
Mary Beth Bauer ◽  
Rebecca L. Brindley ◽  
Mark L. Jewell ◽  
Kevin P. M. Currie
Keyword(s):  
Calcium Channel ◽  
Chromaffin Cells ◽  
Catecholamine Secretion ◽  
Adrenal Chromaffin Cells ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channel ◽  
Adrenal Chromaffin ◽  
Channel Currents
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