Synchronized oscillation of Ca2+ entry and Ca2+ release in agonist-stimulated AR42J cells.
Oscillation in [Ca2+]i induced by agonists has been described in many cell types and is thought to reflect Ca2+ release from and uptake into internal stores. We measured [Ca2+]i and Mn2+ entry in single cells of the pancreatic acinar cell line AR42J loaded with Fura 2 to examine the behavior of Ca2+ influx across the plasma membrane (Ca2+ entry) during agonist-evoked [Ca2+]i oscillation. Addition of extracellular Ca2+ (Ca2+out) to agonist-stimulated cells bathed in Ca2(+)-free medium resulted in a marked [Ca2+]i increase blocked by La3+. The use of Mn2+ as a congener of Ca2+ to follow unidirectional Ca2+ movement reveals an oscillatory activation of Ca2+ entry by Ca2(+)-mobilizing agonists. The frequency at which Ca2+ entry oscillated matched the frequency of Ca2+ release from intracellular stores. Ca2+ entry is activated after completion of Ca2+ release and is inactivated within the time span of each [Ca2+]i spike. These studies reveal a new aspect of [Ca2+]i oscillation in agonist-stimulated cells, that is the oscillatory activation of [Ca2+]i entry during [Ca2+]i oscillation.
Loessberg
P A
PA
Department of Physiology, University of Texas Southwestern Medical Center, Dallas 75235.
Zhao
H
H
Muallem
S
S
D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002451:Cell Compartmentation; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D016257:Fura-2 / Q000031:analogs & derivatives / Q000378:metabolism; D066298:In Vitro Techniques; D010179:Pancreas / Q000378:metabolism*; D010507:Periodicity
C049925:fura-2-am; D004533:Egtazic Acid; D002217:Carbachol; D002118:Calcium; D016257:Fura-2