Folate transport in ileal brush border-membrane vesicles following extensive resection of proximal and middle small intestine in the rat.

Uptake of folic acid (PteGlu) was examined in remnant ileum of rats after resection of 65% of the small intestine with the brush border-membrane vesicle technique. The results were compared to that of sham-operated rats. In both rat groups transport of PteGlu was linear for approximately 40 s of incubation and was similar in the presence of a Na+ and a K+ gradient (out greater than in). In resected rats transport of PteGlu was inhibited by the structural analogues 5-methyltetrahydrofolate (5-CH3H4PteGlu) and methotrexate (MTX), by sulfasalazine, and by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and was saturable as a function of concentration (apparent Kt = 18.3 microM). In the ileum of sham-operated rats, on the other hand, transport of PteGlu was not affected by 5-CH3H4PteGlu, MTX, sulfasalazine, or DIDS and was linear with concentration. These results suggest that the PteGlu transport system is induced in remnant ileum of the rat after extensive intestinal resection.