Single channel and /sup 45/Ca/sup 2 +/ flux measurements of the cardiac sarcoplasmic reticulum calcium channel

Journal Article · Sat Nov 01 04:00:00 EST 1986 · Biophys. J.; (United States)

DOI:https://doi.org/10.1016/S0006-3495(86)83543-3· OSTI ID:7035585

Rousseau, E; Smith, J S; Henderson, J S; Meissner, G

Purified canine cardiac sarcoplasmic reticulum vesicles were passively loaded with /sup 45/CaCl/sub 2/ and assayed for Ca2+ releasing activity according to a rapid quench protocol. Ca2+ release from a subpopulation of vesicles was found to be activated by micromolar Ca2+ and millimolar adenine nucleotides, and inhibited by millimolar Mg2+ and micromolar ruthenium red. /sup 45/Ca/sup 2 +/ release in the presence of 10 microM free Ca2+ gave a half-time for efflux of 20 ms. Addition of 5 mM ATP to 10 microM free Ca2+ increased efflux twofold (t1/2 = 10 ms). A high-conductance calcium-conducting channel was incorporated into planar lipid bilayers from the purified cardiac sarcoplasmic reticulum fractions. The channel displayed a unitary conductance of 75 +/- 3 pS in 53 mM trans Ca2+ and was selective for Ca2+ vs. Tris+ by a ratio of 8.74. The channel was dependent on cis Ca2+ for activity and was also stimulated by millimolar ATP. Micromolar ruthenium red and millimolar Mg2+ were inhibitory, and reduced open probability in single-channel recordings. These studies suggest that cardiac sarcoplasmic reticulum contains a high-conductance Ca2+ channel that releases Ca2+ with rates significant to excitation-contraction coupling.

• Research Organization: Univ. of North Carolina, Chapel Hill
• OSTI ID: 7035585
• Journal Information: Biophys. J.; (United States), Journal Name: Biophys. J.; (United States) Vol. 5; ISSN BIOJA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANIMALS
ATP
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCIUM
CALCIUM 45
CALCIUM ISOTOPES
CATIONS
CELL CONSTITUENTS
CHARGED PARTICLES
CONTRACTION
DAYS LIVING RADIOISOTOPES
DOGS
ELEMENTS
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
MEMBRANE TRANSPORT
METALS
MUSCLES
NUCLEI
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANOIDS
RADIOISOTOPES
SARCOPLASMIC RETICULUM
TRACER TECHNIQUES
VERTEBRATES