Though mammals contain many of the hormone-like substances called prostaglandins, some of the biochemicals only occur in other types of animals. Prostaglandin A2 is a naturally occurring substance that is found in gorgonian corals, where some believe it may play a role in self-defense. More commonly known as sea fans, gorgonian corals are often beautifully colored and are comprised of a colony of polyps supported by an internal branching skeleton made of a flexible, keratin-like substance. Most research regarding prostaglandin A2 indicates that the biochemical exhibits low biological potency in many bioassays, but some studies have shown that it does demonstrate some antiviral and antitumor activity. Investigations have also established that prostaglandin A2 may act as a vasodilator and significantly increase the amount of sodium excreted in the urine.