The influx of uric acid and other purines into everted jejunal sacs of the rat and hamster.

The in vitro transport of [2-14-C]uric acid, [8-14-C]hypoxanthine, and [8-14-C]xanthine, each dissolved in Krebs--Ringer bicarbonate buffer, was studied with everted jejunal sacs from rat and hamster. No evidence could be obtained for the development of a concentration gradient between the intracellular fluid and the incubation medium or between the sac contents and the incubation medium, for any of the three oxypurines. Inhibitiors of active transport, such as anaerobiosis for dinitrophenol, had no significant effect on the rate of transport. A large percentage of hypoxanthine and xanthine was oxidized to urine acid in the sac-wall homogenate, sac contents, and incubation medium during the course of the incubation. This oxidation could be prevented by addition of allopurinol (3 mM) to the incubation medium, but concentration gradients were still not obtained. No active transport mechanism could be demonstrated for uric acid, hypoxanthine, or xanthine in rat or hamster jejunum.