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Cytoplasmic Ca2+ inhibits the ryanodine receptor from cardiac muscle by D. R. Laver; L. D. Roden; G. P. Ahern; K. R. Eager; P. R. Junankar; A. F. Dulhunty is a Biochemistry, Genetics and Molecular Biology article available to read on EtoBox.

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Ca(2+)-dependent inhibition of native and isolated ryanodine receptor (RyR) calcium release channels from sheep heart and rabbit skeletal muscle was investigated using the lipid bilayer technique. We found that cytoplasmic Ca2+ inhibited cardiac RyRs with an average Km = 15 mM, skeletal RyRs with Km = 0.7 mM and with Hill coefficients of 2 in both isoforms. This is consistent with measurements of Ca2+ release from the sarcoplasmic reticulum (SR) in skinned fibers and with [3H]-ryanodine binding to SR vesicles, but is contrary to previous bilayer studies which were unable to demonstrate Ca(2+)-inhibition in cardiac RyRs (Chu, Fill, Stefani & Entman (1993) J. Membrane Biol. 135, 49-59). Ryanodine prevented Ca2+ from inhibiting either cardiac or skeletal RyRs. Ca(2+)-inhibition in cardiac RyRs appeared to be the most fragile characteristic of channel function, being irreversibly disrupted by 500 mM Cs+, but not by 500 mM K+, in the cis bath or by solublization with the detergent CHAPS. These treatments had no effect on channel regulation by AMP-PNP, caffeine, ryanodine, ruthenium red, or Ca(2+)-activation. Ca(2+)-inhibition in skeletal RyRs was retained in the presence of 500 mM Cs+.

Who reads Cytoplasmic Ca2+ inhibits the ryanodine receptor from cardiac muscle?

Author

D. R. Laver; L. D. Roden; G. P. Ahern; K. R. Eager; P. R. Junankar; A. F. Dulhunty

Publisher

Springer; Springer-Verlag; Springer Verlag; Springer Science and Business Media LLC (ISSN 0022-2631)

Published

1995

Language

EN

Field

Biochemistry, Genetics and Molecular Biology (Life Sciences)