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 Lb₅₀ 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.