Identification of hemolytic and neuroactive fractions in the venom of the sea anemone Bunodosoma cangicum

Sea anemones are a rich source of biologically active substances. In crayfi sh muscle fibers, Bunodosoma cangicum whole venom selectively blocks the I- K(Ca) currents. In the present study, we report for the first time powerful hemolytic and neuroactive effects present in two different fractions obtai ned by gel-filtration chromatography from whole venom of B. cangicum. A cyt olytic fraction (Bcg-2) with components of molecular mass ranging from 8 to 18 kDa elicited hemolysis of mouse erythrocytes with an EC50 = 14 mug/ml a nd a maximum dose of 22 mug/ml. The effects of the neuroactive fraction, Bc g-3 (2 to 5 kDa), were studied on isolated crab nerves. This fraction prolo nged the compound action potentials by increasing their duration and rise t ime in a dose-dependent manner. This effect was evident after the washout o f the preparation, suggesting the existence of a reversible substance that was initially masking the effects of an irreversible one. In order to eluci date the target of Bcg-3 action, the fraction was applied to a tetraethylam monium-pretreated preparation. An additional increase in action potential d uration was observed, suggesting a blockade of a different population of KI channels or of tetraethylammonium-insensitive channels. Also, tetrodotoxin could not block the action potentials in a Bcg-3-pretreated preparation, s uggesting a possible interaction of Bcg-3 with Na+ channels. The present da ta suggest that B. cangicum venom contains at least two bioactive fractions whose activity on cell membranes seems to differ from the I-K(Ca) blockade described previously.