The caffeine-sensitive Ca2+ store in bovine adrenal chromaffin cells; an examination of its role in triggering secretion and Ca2+ homeostasis.
The effect of caffeine on catecholamine secretion and intracellular free Ca2+ concentration [( Ca2+]i) in bovine adrenal chromaffin cells was examined using single fura-2-loaded cells and cell populations. In cell populations caffeine elicited a large (approximately 200 nM) transient rise in [Ca2+]i that was independent of external Ca2+. This rise in [Ca2+]i triggered little secretion. Single cell measurements of [Ca2+]i showed that most cells responded with a large (greater than 200 nM) rise in [Ca2+]i, whereas a minority failed to respond. The latter, whose caffeine-sensitive store was empty, buffered a Ca2+ load induced by a depolarizing stimulus more effectively than those whose store was full. The caffeine-sensitive store in bovine chromaffin cells may be involved in Ca2+ homeostasis rather than in triggering exocytosis.
Cheek
T R
TR
Department of Zoology, University of Cambridge, UK.
O'Sullivan
A J
AJ
Moreton
R B
RB
Berridge
M J
MJ
Burgoyne
R D
RD
D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D003593:Cytoplasm / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D006706:Homeostasis; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology; D012636:Secretory Rate / Q000187:drug effects
D002395:Catecholamines; D008688:Methacholine Compounds; D016210:Methacholine Chloride; D002110:Caffeine; D004533:Egtazic Acid; D009538:Nicotine; D008274:Magnesium; D002118:Calcium