Kinetics of Uric Acid Transport and Its Production in Rat Small Intestine

Segments of the middle third of rat small intestine were incubated at 30 °C for 1 hour in the model of Crane and Wilson. When comparison was made between the uric acid contained in unincubated segments and that in both incubated segments and their incubation media, the latter was found to exceed the former nearly fivefold. This indicates that the small intestine is a major site of uric acid production in the body. The rate of uric acid-14C transport across the intestinal wall was studied with the same model, and found to be linearly proportional to its initial concentration gradient in both directions. This rate was not altered by hypoxanthine or uricosuric agents, which have been shown to influence uric acid transport in other systems. It is concluded, therefore, that uric acid transport across the wall of the small intestine is by passive diffusion.