Near-membrane [Ca2+] transients resolved using the Ca2+ indicator FFP18
UMass Chan Affiliations
Department of Physiology and Biomedical Imaging GroupDocument Type
Journal ArticlePublication Date
1996-05-28Keywords
AnimalsBufo marinus
Calcium
Cell Membrane
Chelating Agents
Cytosol
Fluorescent Dyes
Fura-2
Kinetics
Mathematics
Membrane Potentials
Models, Biological
Muscle, Smooth
Patch-Clamp Techniques
Stomach
Life Sciences
Medicine and Health Sciences
Metadata
Show full item recordAbstract
(Ca2+)-sensitive processes at cell membranes involved in contraction, secretion, and neurotransmitter release are activated in situ or in vitro by Ca2+ concentrations ([Ca2+]) 10-100 times higher than [Ca2+] measured during stimulation in intact cells. This paradox might be explained if the local [Ca2+] at the cell membrane is very different from that in the rest of the cell. Soluble Ca2+ indicators, which indicate spatially averaged cytoplasmic [Ca2+], cannot resolve these localized, near-membrane [Ca2+] signals. FFP18, the newest Ca2+ indicator designed to selectively monitor near-membrane [Ca2+], has a lower Ca2+ affinity and is more water soluble than previously used membrane-associating Ca2+ indicators. Images of the intracellular distribution of FFP18 show that >65% is located on or near the plasma membrane. [Ca2+] transients recorded using FFP18 during membrane depolarization-induced Ca2+ influx show that near-membrane [Ca2+] rises faster and reaches micromolar levels at early times when the cytoplasmic [Ca2+], recorded using fura-2, has risen to only a few hundred nanomolar. High-speed series of digital images of [Ca2+] show that near-membrane [Ca2+], reported by FFP18, rises within 20 msec, peaks at 50-100 msec, and then declines. [Ca2+] reported by fura-2 rose slowly and continuously throughout the time images were acquired. The existence of these large, rapid increases in [Ca2+] directly beneath the surface membrane may explain how numerous (Ca2+)-sensitive membrane processes are activated at times when bulk cytoplasmic [Ca2+] changes are too small to activate them.Source
Proc Natl Acad Sci U S A. 1996 May 28;93(11):5368-73.