Uric acid serves no known useful function in the mammalian body. It is the end product of the metabolism of purines which are in turn a product of the breakdown of proteins of the cell nucleus. Nursing animals on a diet exclusively of milk have a diet devoid of purine.

In most mammals, presumably including those marine cetaceans studied, uricase, an enzyme in the liver breaks down uric acid and leaves very low blood levels. Man, ape, the Dalmatian dog, and presumably Inia geoffrensis (Ridgway et al. 1970) lack this enzyme. The interesting thing about Inia is that the values found are much higher than normal human values. In fact, uric acid levels in the Amazon River dolphins tested have usually been higher than the 6.4 mg/100 ml concentration at which uric acid saturates human blood and starts to precipitate out resulting in the disease of gout. Cutaneous gout (uric acid crystals concentrated in skin lesions) with a uric acid blood level of 14.4 mg/100 ml has been reported in one Inia during its sixth year of captivity. The animal was successfully treated with a gout medicine, allopurinol (Garman et al., 1983). We do not know the full physiological significance of the high uric acid levels in Inia.

While Tursiops truncatus does not normally have high blood uric acid levels, we have observed cases of uric acid kidney stones in animals over the age of 12 years. We suggest that these kidney stones have clinical significance and that means should be found for their diagnosis and treatment.