Digestion of orally administered lactoferrin in adult rats

The understanding of the changes in the structure and function of lactoferrin that occur following ingestion of this protein, remains an important goal. Rats were given free access to milk enriched with bovine lactoferrin at 40 mg/ml (5 x 10(-7) mol/g). Employing a SELDI affinity mass spectrometric assay for lactoferrin fragments, various kinds of degraded lactoferrin fragments in the gastrointestinal tract were simply detected as molecular-ion peaks corresponding to lactoferricin. The level of lactoferrin fragments detected in the contents of the lower small intestine was approx. 1 x 10(-9) mol/g. We further explored the distribution of lactoferrin and its fragments after oral administration of a single dose of I-125-labeled lactoferrin using whole-body autoradiography. The radioactivity in the gastrointestinal tract remained high at 180 min postadministration. Lactoferrin fragments containing the lactoferricin region were also detected by SELDI affinity mass spectrometry in the small intestine after administration of a single dose of lactoferrin. Therefore, it is concluded that ingested lactoferrin survives transit through the gastrointestinal tract of adult rats as partially degraded forms containing the lactoferricin region (i.e., the region essential for receptor binding and the antimicrobial active center of lactoferrin), in the case of both ad libitum feeding and single dose administration