[Detection of transferrin in the digestive juices of rat and its possible role in iron absorption from the small intestine].

Presence of transferrin in digestive juices and its possible role in iron absorption of rats were examined. Transferrin concentrations in saliva, bile, pancreas juice and intestinal fluid obtained from adult rats of the Wistar strain were measured by Rocket immunoelectrophoretic assay. Transferrin concentration in pancreas juice was the highest (approximately 0.28 mg/ml) in the collected digestive juices and the concentration in iron deficient rats was 4 times higher than that of normal rats. The iron saturation rate of transferrin in pancreas juice was approximately 40%. The participation of transferrin in iron absorption was investigated by the absorption through the intestinal segment of rats, into which 59Fe labeled diferric transferrin was injected. The rate of iron absorption was more efficient in duodenal and proximal segments compared to the distal segment of the small intestine. The value was approximately 20% in the duodenal segment but less than 2% in the ileal segment. Iron absorption from diferric transferrin in the duodenal segment was inhibited by 1 mM monodansylcadaverine, the inhibitor of endocytosis, or addition of 20 times the normal amounts of nonradioactive transferrin in the test material. These data indicated that the process of iron absorption through diferric transferrin was not a passive phenomenon. Furthermore, one hour after the absorption of diferric 125I-labeled transferrin in the proximal segment of the small intestine, 125I-labeled transferrin was detected from the mucosal tissue of the segment, the luminal surface of which had been treated by 0.25% pronase E before the mucosal scraping.(ABSTRACT TRUNCATED AT 250 WORDS)