Abstract
Three models of cardiac hypertrophy (aortic constriction, application of isoproterenol, daily injections of triiodothyronine) were characterized in haemodynamic and in metabolic terms. Heart function was evaluated in closed-chest rats after catheterization of the left ventricle with an ultraminiature catheter pressure transducer. Heart rate (HR), left ventricular systolic pressure (LVSP), and the maximal rate of rise of left ventricular pressure (LV dP/dtmax) were measured. The metabolic parameters determined included the levels of cardiac cyclic AMP and the rates of the biosynthesis of myocardial adenine nucleotides. During the first 72 h after aortic constriction, HR was decreased, whereas LVSP and LV dP/dtmax were both elevated. Within 12 h after administration of isoproterenol, HR and LV dP/dtmax were markedly increased, while LVSP was depressed. In triiodothyronine-treated animals, all haemodynamic parameters were elevated during the first 72 h. Comparison with the time course of changes in metabolic parameters revealed that the rise in cardiac contractility measured as LV dP/dtmax occurred at about the same time as the increase in the content of myocardial cyclic AMP in the isoproterenol- and triiodothyronine-models. In hypertrophy due to aortic constriction, cardiac cyclic AMP was elevated only moderately, and this elevation did not correlate with the enhancement of contractility. Beta-receptor-blockade with propranolol prevented entirely the increase of myocardial adenine nucleotide biosynthesis in the isoproterenol- and triiodothyronine- but not in pressure-induced hypertrophy.
Published Version
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