Possible cyclic nucleotide regulation of calcium mediating myocardial contraction

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Science  11 Mar 1977:
Vol. 195, Issue 4282, pp. 982-990
DOI: 10.1126/science.14399


An inhibitor of adenylate and guanylate cyclases was tested on strips of left atria from rabbits. Effects of catecholamines (cardiotonic) and of acetylcholine (cardiodepressive) were blocked, and positive force-frequency was converted to negative. Ouabain produced only contracture without positive inotropy. The cardiotonic effect of increased calcium remained. Data suggest that cyclic nucleotides modulate calcium associated with these stimuli.