Key result
Eugenol depressed force in rat cardiac muscle without affecting the contractile machinery, acting solely through blockade of the calcium inward current.
Eugenol acts as a negative inotrope in rat cardiac muscle primarily through the blockade of inward calcium currents rather than direct effects on contractile proteins.
Eugenol may depress cardiac force via calcium current blockade; leaves open translation to human myocardium or clinical relevance.
Eugenol (EUG) acts as a calcium antagonist but effects on the contractile proteins could also occur. We investigated inotropic effects of EUG in rat left ventricular papillary muscles, measuring isometric force, time variables, and post rest potentiation and EUG actions on the effects of Ca2+ (0.62 to 2.5 mM) and isoproterenol (5 ng/ml), on myosin ATPase activity and on the calcium currents in single ventricular myocytes. EUG reduced tension and time variables without altering the sarcoplasmic reticulum activity increasing post-pause relative potentiation. Isoproterenol and Ca2+ counteract these negative inotropic effects. Tetanic tension diminished, but not the myosin ATPase activity suggesting an isolated sarcolemmal effect. EUG 0.1 mM decreased the Ca2+ current amplitude in the entire potential range tested and 0.5 mM almost completely blocked this inward current. Results suggested that EUG depresses force without affecting the contractile machinery and its action is the only dependent blockade of the calcium inward current.
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Damiani et al. (2004) studied this question. Eugenol was evaluated on Mechanical and electrical activities of cardiac muscle (isometric force, calcium currents). Eugenol depressed force in rat cardiac muscle without affecting the contractile machinery, acting solely through blockade of the calcium inward current.
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