Frequency-Dependent Inhibition of the Intracellular Calcium Transients by Calmodulin Antagonists in the Aequorin-Injected Rabbit Papillary Muscle
Calmodulin, a ubiquitous functional protein in eukaryotic cells, has been found to play an essential role in regulation of enzymes and cellular processes in various tissues including smooth muscle cells (Cheung, 1980; Klee and Newton, 1985), Although it has been shown that calmodulin exists in myocardial cells and suggested that it may be involved in regulation of myocardial functions, based on the effects of calmodulin on enzyme activities and Ca2+uptake, its regulatory role in intact myocardium remains unclear. In order to get insight into the role of calmodulin in regulation of myocardial contractility, the effects of calmodulin antagonists, W-7 and trifluoperazine (TFP), on the intracellular calcium transients and isometric contractions were assessed simultaneously in the isolated rabbit papillary muscle, superficial cells of which had been microinjected with the Ca2+ sensitive bioluminescent protein aequorin.
KeywordsPapillary Muscle Isometric Contraction Calcium Transient Stimulus Interval Myosin Light Chain Phosphorylation
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