Action of trapidil on the heart contractility: relationship to the cyclic nucleotide metabolism.

The relationship between the cardiotonic action of trapidil (RocornalR) and cyclic nucleotide metabolism was studied in the isolated rat heart. The contractility of the heart was increased in a concentration-dependent manner by this drug (ED50 20/microM). Parallel with the mechanical changes the tissue levels of cyclic AMP were increased, which was associated with an activation of the cAMP-dependent protein kinase. Cyclic GMP was enhanced only at a drug concentration of 1 mM. The present findings support the hypothesis that the cyclic nucleotide system is involved in the functional action of trapidil on cardiac tissue.