Absorption of labeled simple 3',5',9'-(3)H pteroylmonoglutamate, ([(3)H]PG-1) and conjugated pteroyl-mu[(14)C]glutamyl-gamma-hexaglutamate, ([(14)C]PG-7) folates was assessed in six patients with
tropical sprue, before and after 6 mo of treatment, utilizing jejunal perfusion and urinary recovery techniques. Degradation products of [(14)C]PG-7 which were produced during perfusion were identified by
DEAE-cellulose column chromatography. Jejunal mucosal activities of
folate conjugase,
lactase,
sucrase, and
maltase were measured in every patient. Malabsorption of both [(3)H]PG-1 and [(14)C]PG-7 was found in every untreated patient, with significant improvement after
therapy. The urinary excretion of (3)H and (14)C paralleled the
luminal disappearance of both
isotopes. The chromatographic patterns of intraluminal degradation products of [(14)C]PG-7 obtained during perfusion did not differ from those previously found in normal subjects and were similar in studies performed before and
after treatment. The activity of
folate conjugase was increased in the mucosa of the untreated patients when compared to the post-treatment levels while the activities of mucosal
lactase,
sucrase, and
maltase were originally low and increased significantly after
therapy. These observations suggest that
folate conjugase originates at a different mucosal locus than the brush border
disaccharidases, and are consistent with previous evidence that
folate conjugase is an intracellular
enzyme. The present studies have demonstrated unequivocal malabsorption of both simple and conjugated folates in
tropical sprue. In
tropical sprue,
folate malabsorption is the reflection of impaired
folate transport and not of impaired hydrolysis.