Why poison dart frogs don't poison themselves

September 5, 2017 by Bob Yirka report

 (Phys.org)—A pair of researchers with the State University of New York has found the source of poison dart frogs' immunity from their own poison. In their paper published in Proceedings of the National Academy of Sciences, Sho-Ya Wang and Ging Kuo Wang describe testing frog muscle-derived amino acids in rat muscles to determine if one of them might be responsible for preventing muscle from seizing.

Poison dart frogs, native to Columbia, are known throughout the world for the application of their poison to blow darts as a weapon. The toxin is produced in the skin gland and one frog holds enough to kill 10 human beings at any one time—the toxin kills by reversing the openings of sodium channels in nerves, which prevents muscles from relaxing. The heart clenches to push blood through the body, but then cannot unclench, preventing it from working.

Prior research has shown that the active ingredient in the toxin is batrachotoxin. To figure out why the dart frogs do not give themselves heart attacks when they produce the chemical, the researchers introduced five naturally occurring amino acid replacements found in the frog's muscles into rat muscles. Doing so, the researchers report, made the rat muscle immune to the effects of batrachotoxin. The researchers then tested the amino acids individually until they found the one that was responsible for the change—N1584T. This finding overturns prior research results that suggested multiple factors were responsible for frog immunity—it shows that the immunity in the frogs comes from a single genetic mutation.

Unfortunately, as with the puffer fish, which was also found to have just one amino acid that protected it from harming itself, this discovery is not likely to offer a path to an antidote for those who fall prey to the effects of dart frog toxin. It might offer new data, however, for those conducting research involving using the toxin as a pain killer.

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