Nature is chock full of toxins. Toxins come from all five kingdoms of life — bacteria, fungi, protists, plants and animals. Although the toxins span a broad range of shapes, sizes, and potencies, they’re all produced for the same reason: warfare.
Toxins come in two main flavors: as proteins and as small organic molecules. The protein toxins are both big and small. The small organic molecule toxins are very small.
What’s a small organic molecule? You probably know it as a (prescription) drug. Check out the image below:
This image is a compilation of pills your doctor prescribes to treat a variety of ailments. Inside each colorful little package is one type of small organic molecule.
So a toxin can take drug form or protein form, both of which can enter your body and reek havoc.
The tropical pufferfish, especially prevalent in Japan, carries a small organic molecule toxin — the very small drug kind.
Here’s an adorable, cuddly pufferfish:
The drug-like toxin found in pufferfish is called tetrodotoxin. An interesting little technicality is: the pufferfish itself does not make the toxin, but rather bacteria living inside the pufferfish produce it!
Tetrodotoxin is one of the most potent toxins out there. If you eat the equivalent of a grain of salt, you’re a goner. One tenth of that has the same result. One hundredth of that: same result.
Tetrodotoxin affects a cell’s sodium channel. If you haven’t read my last post, “Your potassium channel,” now would be the time.
The sodium channel has the same functionality as the potassium channel. The difference is only the type of stuff the channel flushes out and takes in. For a potassium channel, the type of stuff is potassium. For a sodium channel, the type of stuff is sodium.
We’ve learned that we don’t want to mess with these channels, because messing with the channels inhibits the cells from communicating with each other. And, just like with potassium, cells use sodium to talk. For example:
Cell 1: “Hey, did you see the latest episode of ‘Glee?’”
Cell 2: “Yeah, those New Horizons kids totally nailed it!”
I jest. Cells don’t talk about “Glee.” (Although they should.)
Most toxins affect the cells of the nervous system. So the type of cell that’s of interest here is the nerve cell. On a normal day, the nerve cell opens and closes its sodium channel, flushing out sodium, taking in sodium, all the while transmitting electrical signals to its neighbor cells.
Let’s say I have a hankering for pufferfish. I eat one. I now have tetrodotoxin loose inside my body. The very, very tiny tetrodotoxin finds its way to the sodium channels in my nerve cells.
A tetrodotoxin molecule plops itself down in a channel’s opening. That channel can no longer open or close. The sodium inside the cell cannot get out. The sodium outside the cell cannot get in.
Now that poor nerve cell can’t communicate; it has lost its ability to regulate itself. It dies. The cells around it die, too. Soon, enough cells have died that I’m paralyzed. Oops.
Another toxin that plugs a cell’s sodium channel is called batrachotoxin. This drug-like toxin is produced by the poison dart frog. How cute is this little guy?
Besides sodium channel toxins, nature has potassium and calcium channel toxins, too. Scorpions, for example, produce protein toxins targeting the potassium channel of a nerve cell. Whew. I’d hate for the poor sodium channel to be singled out for destruction.
The black mamba snake, the largest venomous snake in Africa, produces a large protein toxin called calciseptine. Calciseptine targets the calcium channel, as you may have guessed from its similar name. This particular toxin is such effective warfare that the black mamba snake eats like a king.
Here’s a black mamba snake eating some unfortunate rodent:
Don’t eat black mamba snakes. Also, don’t eat scorpions. Also, don’t. eat. pufferfish.