Dose-dependency in spatial dynamics of [Ca2+]c in adrenal chromaffin cells.
The spatial dynamics of cytosolic Ca2+ concentration, [Ca2+]c, in guinea pig adrenal chromaffin cells was monitored by a digital image analysing technique using Fura-2. When a freshly isolated cluster of cells was stimulated with lower concentrations of carbachol (CCh; 0.3-1 microM), the [Ca2+]c began to increase in the region beneath the plasma membrane facing the extracellular environment. The [Ca2+]c increase depended on the presence of extracellular Ca2+ ([Ca2+]o). CCh at a higher concentration (100 microM), however, caused [Ca2+]c increase even in the absence of [Ca2+]o. These results are compatible with the view that the receptor activation with a physiological concentration of secretagogue accelerates Ca2+ entry, and that stimulation with a higher concentration of the secretagogue induces small transient Ca2+ release from intracellular stores and predominant continuous Ca2+ entry.
Kanno
T
T
Department of Physiology, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Habara
Y
Y
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001692:Biological Transport; D002118:Calcium / Q000032:analysis / Q000493:pharmacokinetics* / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D002838:Chromaffin System / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D003600:Cytosol / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005453:Fluorescence; D016257:Fura-2; D006168:Guinea Pigs; D007091:Image Processing, Computer-Assisted; D008297:Male
D001285:Atropine; D002217:Carbachol; D002118:Calcium; D016257:Fura-2