The 5-hydroxytryptamine content of rabbit hearts and its release during in vitro perfusion

Abstract

Abstract Rabbit hearts were perfused in vitro at constant pressure by the Langendorff technique. After 30 min perfusion, hearts from untreated animals contained significantly more 5-HT than those from animals pretreated with heparin. The cardiac 5-HT content of the non-heparinized group decreased during a further 55 min perfusion and the amount lost from the hearts was equal to that recovered from the perfusion fluid. In contrast, the 5-HT content of hearts from heparinized animals did not change significantly during this period, and no 5-HT could be detected in the perfusates. Investigation of the distribution of 5-HT within the hearts from heparinized animals disclosed a significantly greater concentration of 5-HT in the right atrium than in the rest of the heart. It is concluded that the small, perfusion-resistant store of 5-HT within hearts from heparinized rabbits represents the true endogenous 5-HT content in this species, but that much higher values may be obtained unless care is taken to exclude a contribution from blood platelets.