Cardiac effects of Stomolophus meleagris (cabbage head jellyfish) toxin

Electrocardiograms recorded from rabbits and rats injected intravenously with toxin from Stomolophus meleagris showed bradycardia followed by inversion of the P and T waves, alterations of the QRS complex, ventricular extrasystoles, atrioventricular block, bizarre ventricular patterns, and fibrillation. Analysis of plasma samples taken after the onset of electrocardiographic abnormalities were characterized by hemolysis, hyponatremia and hyperkalemia when compared to plasma taken before injection of toxin. Sublethal doses of toxin produced an increase in lactate dehydrogenase (LDH) levels in serum, but did not increase creatine phosphokinase levels. Electrophoretic analysis of the serum LDH isoenzymes following injection of toxin did not indicate severe cardiac tissue damage. This toxin appears to disrupt cardiac rhythmicity and myocardial conduction pathways in a manner consistent with other coelenterate toxins. The observed hyperkalemia appears to result from hemolysis and generalized tissue destruction, although the serum enzyme and isoenzyme assays did not suggest severe myocardial infarction.