Title

Near-membrane [Ca2+] transients resolved using the Ca2+ indicator FFP18

UMMS Affiliation

Department of Physiology and Biomedical Imaging Group

Publication Date

1996-05-28

Document Type

Article

Subjects

Animals; Bufo marinus; Calcium; Cell Membrane; Chelating Agents; Cytosol; Fluorescent Dyes; Fura-2; Kinetics; Mathematics; Membrane Potentials; Models, Biological; Muscle, Smooth; Patch-Clamp Techniques; Stomach

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

(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.

Journal/Book/Conference Title

Proceedings of the National Academy of Sciences of the United States of America

Related Resources

Link to Article in PubMed

PubMed ID

8643581

Link to Full Text

Share

COinS