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Paralysis of frog skeletal muscle fibres by the calcium antagonist D‐600.
Author(s) -
Eisenberg R S,
McCarthy R T,
Milton R L
Publication year - 1983
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1983.sp014819
Subject(s) - biophysics , chemistry , endoplasmic reticulum , calcium , caffeine , stimulation , skeletal muscle , membrane potential , contracture , anatomy , medicine , biology , biochemistry , surgery , organic chemistry
The Ca2+ channel blocker D‐600 (methoxyverapamil) paralyses single muscle fibres of the frog: fibres exposed to the drug at 7 degrees C give a single K+ contracture after which they are paralysed, unable to contract in response to electrical stimulation or further applications of K+. Paralysed fibres contract in response to caffeine and have normal resting potentials and action potentials. Fibres treated with D‐600 at 22 degrees C are not paralysed. Paralysed fibres warmed to 22 degrees C recover contractile properties: they twitch and give K+ contractures. Other workers have shown that D‐600 blocks a Ca2+ channel at room temperature; thus, the paralytic action of D‐600 is probably mediated by a different membrane protein, perhaps a different Ca2+ channel from that blocked at room temperature. These results suggest that the binding of D‐600 can disrupt the mechanism coupling electrical potential changes across the T membrane to Ca2+ release from the sarcoplasmic reticulum.