Key result
Denopamine and isoproterenol increased heart rate and left ventricular oxygen consumption to a comparable extent at a comparably increased contractility in excised cross-circulated dog hearts.
Why the study?
Does denopamine compared to isoproterenol differentially affect heart rate and myocardial oxygen consumption in excised cross-circulated dog hearts?
Does denopamine compared to isoproterenol differentially affect heart rate and myocardial oxygen consumption in excised cross-circulated dog hearts?
In isolated and denervated dog hearts, the degree of beta1-selectivity of a beta-agonist does not directly determine the relative potencies of its inotropic and chronotropic effects or the oxygen cost of contractility.
Challenges beta1-selectivity as determinant of chronotropic-inotropic balance or oxygen cost; leaves open relevance to intact hearts.
The effects of denopamine (a beta 1-selective adrenergic receptor agonist) and isoproterenol (a non-selective beta-adrenergic receptor agonist) on heart rate, left ventricular contractility, and left ventricular oxygen consumption (VO2) at the same left ventricular volume were compared in excised cross-circulated dog hearts. Denopamine and isoproterenol increased heart rate and VO2 to a comparable extent at a comparably increased contractility. Moreover, the oxygen cost of contractility which quantifies VO2 for excitation-contraction coupling was the same between the two agents. These findings contradict the previously reported smaller increases in heart rate and VO2 by denopamine than by isoproterenol in open-chest dog hearts, which have been mainly attributed to the beta 1-selectivity of denopamine. Our results suggest that in isolated and denervated hearts, the degree of beta 1-selectivity of a beta-agonistic agent does not directly determine the relative potencies of its inotropic and chronotropic effects and the oxygen cost of contractility.
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Futaki et al. (1991) studied this question. Denopamine vs. Isoproterenol was evaluated on Heart rate, left ventricular contractility, and left ventricular oxygen consumption (VO2). Denopamine and isoproterenol increased heart rate and left ventricular oxygen consumption to a comparable extent at a comparably increased contractility in excised cross-circulated dog hearts.
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