Purification of a toxic factor from Arabian Gulf catfish epidermal secretions

The Arabian Gulf catfish, Arius bilineatus (Valenciennes) secretes a proteinaceous epidermal secretion when threatened or injured. A toxic factor has been isolated and purified from the crude extract (crude skin toxin) of these secretions by a combination of gel filtration on Sephacryl S-300 and preparative discontinuous polyacrylamide gel electrophoresis. The purified skin toxin has a molecular weight of 39,000 Da and an isoelectric point (pI) of 5.45. Injection of the purified skin toxin into rabbits i.v. and determination of the LD50 indicated that the protein had been purified approximately 30 fold by these procedures. Injection of the purified skin toxin into rabbits caused agitation, convulsions and death within 5 min. Analysis of plasma levels of lactate dehydrogenase, glutamate-oxaloacetate transaminase and glutamate pyruvate transaminase in injected rabbits indicated that the skin toxin caused cardiac and liver damage to the animals.