Shark Rectal Gland

I can now check off the box entitled "Dissect out and do experiments on a shark's rectal gland" on my master "To Do" list of life.

Why would a bunch of kidney doctors study the shark's rectal gland, you may ask? It turns out this interesting gland has played an integral role in understanding how salt is handled by the kidney.

The shark lives in the ocean--where the salt concentration is extremely high. Yet their blood salt concentration is essentially the same as that of humans. The shark rectal gland's function is to continually excrete sodium at high concentrations which enables it to live in such a salty environment. In contrast, in humans regulation of the sodium concentration occurs in the kidney--but using many of the same proteins that are found in the shark rectal gland, hence its relevance to nephrologists.

Here I am wrestling a small spiny dogfish shark.

Dissecting the underbelly of the shark allows one to easily identify the shark rectal gland--the brownish, worm-like structure which is a little less than the size of my pinky finger.
The next step is to bring the rectal gland back to the lab, where you can hook up its artery to a perfusion catheter (left) and hook up its duct and vein to catheters which monitor its output (the two tubes coming out on the right). Different chemicals added to the gland cause it to secrete more or less salt. The greenish stuff is just mounting clay, to hold the gland in place. The glass hot-dog-shaped object upon which the rectal gland rests has seawater pumped into it to keep the specimen cool. This has to definitely be one of the coolest, most mad-scientisty things I've done so far...