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

Abstract

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.