Functional fragments of ingested lactoferrin are resistant to proteolytic degradation in the gastrointestinal tract of adult rats

Pharmaceutical and food-related applications of lactoferrin, an 80-kDa iron -binding glycoprotein found predominantly in milk, have attracted interest lately, but the process of digestion of lactoferrin has been poorly charact erized. The digestive fate of bovine lactoferrin in adult rats after oral a dministration of a single dose and after dietary supplementation was studie d by I-125-labeling and by surface-enhanced laser desorption/ionization (SE LDI) affinity mass spectrometry. The latter method was designed to detect m ultiple forms of degraded lactoferrin as simple molecular ion peaks corresp onding to one of the core regions of lactoferrin, namely, the lactoferricin region (Phe17-Ala42). Radioactive fragments with molecular masses of 42, 3 6, 33 and 29 kDa were observed at 20, 60 and 180 min postingestion in the c ontents of the lower small intestine. Rats were given free access to milk e nriched with lactoferrin at 482 mu mol/L (40 mg/mL). The concentrations of lactoferrin fragments in the contents of the stomach, small intestine and l ower small intestine as determined by SELDI affinity mass spectrometry were similar to 200, 20 and 1 mu mol/L, respectively. These data indicate that functional fragments of LF such as fragments containing glycosaminoglycan-b inding site(s), as well as large fragments with a mass >20 kDa, indeed surv ive proteolytic degradation in the small intestine of adult rats.