Abstract
Summary
Myocardial cyclic-AMP was measured by Brooker's enzymatic isotopic displacement method and an independent method employing skeletal muscle protein kinase in hearts from guinea pigs with congestive heart failure induced by thoracic aortic constriction, sham operated controls, and normal animals under basal conditions and 15 sec after graded doses of epinephrine. Cyclic-AMP content was 7.4 ± 0.6 (mean ± SE) and 8.2 ± 0.6 pmoles/mg of protein in failing and normal hearts, respectively, under basal conditions. With maximum epinephrine stimulation, values increased to 18.1 ± 0.9 and 16.9 ± 1.5, respectively. There were no significant differences in cyclic-AMP content in failing, compared to normal, hearts at any epinephrine dose. Results indicate that there is no impairment in the overall capacity of the intact, failing heart to synthesize cyclic-AMP in response to exogenous catecholamines.
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