THE CORONARY VASOCONSTRICTOR ACTION OF EXTRACT-IV FROM THE DAHLIA SEA-ANEMONE TEALIA-FELINA L

Extract IV, a partially purified preparation of the toxin from the sea anemone Tealia felina, produced marked bradycardia and arrhythmias in the rat in vivo. In the Langendorff rat heart preparation perfused at constant pressure extract IV (0.0224 AU/ml) reduced the force of cont raction by 81.3 +/- 7.2%, n = 6, and the coronary flow by 82.0 +/- 4.7 %, n = 5. When the preparation was perfused at constant flow rate, ext ract IV (0.072 AU/ml) increased the coronary circulation resistance fr om 3.76 +/- 1.09 (control) to 36.94 +/- 12.26 mm Hg/ml/min. The force of contraction was also markedly reduced. The extract produced bradyca rdia in preparations perfused at constant pressure but not in those pe rfused at constant flow rate. The extract did not affect isolated atri a preparations. It was concluded that the bradycardia produced in vivo and in preparations perfused in vitro at constant pressure was probab ly secondary to the coronary vasospasm produced, which could contribut e to the cardiotoxicity of the extract.