Effects of ftorafur and 5-fluorouracil on the canine sinoatrial node

Effects of ftorafur and 5-fluorouracil (5-FU) on the canine sinoatrial node were studied using isolated sinoatrial node and an atrial preparation which were obtained from puppies and perfused with oxygenated Tyrode solution through the dorsal right atrial artery (sinus node artery). The injection of ftorafur and 5-FU caused positive inotropic and chronotropic effects. However, the solvent of 5-FU caused similar effects. These positive inotropic and chronotropic effects were not abolished by pindolol. Verapamil did not alter the effects of ftorafur and 5-FU. Also a change in extracellular calcium concentration and aminophylline did not affect the positive chronotropic and inotropic responses to the two agents. These findings suggest that ftorafur may induce the positive responses by direct action.