Back to IndexBufo marinus (Cane toad/Marine toad)
The major clinical effects by members of the bufo genus,
particularly the large and ubiquitous B. marinus (Marine toad), are
primarily cardioactive due to digoxin-like cardiotonic steroids present
in the venom. The clinical symptoms, besides dermatitis, are hypotension
accompanied by potentially severe arrhythmia. A significant degree of the
clinical effects may be due to assimilated plant alkaloids that have been
put to use in the defence system(Radford, Gillies et al. 1986). In a case
where two Japanese women tried to commit suicide using the traditional Chinese
medicine Kyushin, of which toad venom is the primary active component, the
clinical effects were a significant elevation of a serum digoxin-like immunoreactive
substance (2.35 and 1.84 ng/ml) and symptoms of nausea, vomiting and general
malaise. Their blood biochemistry and electrolytes were normal. In one patient,
an electrocardiogram revealed a second degree Wenckebach atrioventricular
block and T-wave change (Lin, Lin et al. 1989).
Bufo toad venom derived cardiotonic steroids, isolated from B. marinus venom, are bufotalin, marinobufagen, marinoic acid, and resibufogenin, all of which inhibit Na+,K(+)-ATPase activity. Bufotalin has a higher potency for inhibition of myocardial Na+,K(+)-ATPase activity than digoxin increasing the myocardial contractile force but did not affecting the heart rate (Hirai, Morishita et al. 1992). Marinobufagenin, similar to ouabain, possesses potent vasoconstrictive activity with higher digoxin-like immunoreactivity than ouabain (Bagrov, Roukoyatkina et al. 1995). Marinoic inhibits Na+, K+, -ATPase enzymatic activity, and 3H ouabain binding to the digitalis receptor set on Na+, K(+) ATPase. However, marinoic acid was less effective inhibitor than typical bufadienolides (Matsukawa, Akizawa et al. 1996). Resibufogenin, 3-hydroxy-14,15 -epoxy-20,22-dienolide, has the same structure as bufalin except for one H+ and is also a potent sodium pump inhibitor (Pamnani, Chen et al. 1994) The electrophysiological characteristics and electrophysiological properties of RBG are similar to that of acetylstrophanthidin (AS), suggesting that RBG belongs to the family of digitalis-like drugs (Xie, Cunningham et al. 1994).
