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Biphasic inotropic effects of a Ca 2+ channel activator CGP28392 in rat myocardium: possible relation to intracellular Ca 2+ release
Author(s) -
Kobrinsky Evgeny,
Saxon Maya
Publication year - 1987
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1987.tb11349.x
Subject(s) - inotrope , contraction (grammar) , intracellular , endoplasmic reticulum , activator (genetics) , medicine , endocrinology , muscle contraction , cardiac muscle , chemistry , stimulation , channel blocker , biophysics , calcium , biology , biochemistry , receptor
1 The inotropic effect of a Ca 2+ ‐entry stimulator, CGP28392, (CGP) was compared in rat and frog myocardium in a concentration‐and time‐dependent manner. 2 Frog preparations exhibited a persistent positive inotropic effect following prolonged treatment with CGP. 3 Compared to amphibian myocardium, rat ventricular muscle exhibited a biphasic time‐dependent response to CGP: an initial increase in the twitch tension amplitude of 30% was changed to a reduction of 80% below the control level during prolonged exposure to CGP (stimulation frequency, 0.2 Hz). 4 Following prolonged incubation with CGP, the resting‐state contraction was decreased and the negative force‐frequency relation was converted into a positive one in rat muscle. 5 Since sarcoplasmic reticulum (SR) is the major source of Ca 2+ in a rested‐state contraction, inhibition by CGP suggests an additional, intracellular action of the Ca 2+ channel activator on SR‐Ca 2+ release in rat myocardium.