Colocalization of calcium entry and exocytotic release sites in adrenal chromaffin cells.
"Snapshot" images of localized Ca2+ influx into patch-clamped chromaffin cells were captured by using a recently developed pulsed-laser imaging system. Transient opening of voltage-sensitive Ca2+ channels gave rise to localized elevations of Ca2+ that had the appearance of either "hotspots" or partial rings found immediately beneath the plasma membrane. When the Ca2+ imaging technique was employed in conjunction with flame-etched carbon-fiber electrodes to spatially map the release sites of catecholamines, it was observed that the sites of Ca2+ entry and catecholamine release were colocalized. These results provide functional support for the idea that secretion occurs from "active zone"-like structures in neuroendocrine cells.
Robinson
I M
IM
Department of Physiology and Biophysics, Mayo Clinic, Rochester, MN 55905, USA.
Finnegan
J M
JM
Monck
J R
JR
Wightman
R M
RM
Fernandez
J M
JM
D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D004594:Electrophysiology / Q000379:methods; D005089:Exocytosis; D013050:Spectrometry, Fluorescence
D002395:Catecholamines; D002118:Calcium