Trans-endothelial and trans-epithelial transfer of lactoferrin into the brain through BBB and BCSFB in adult rats.

The transportation of intravenously administered bovine lactoferrin (bLF) into the cerebrospinal fluid (CSF) was immunohistochemically investigated in adult rats. Administered bLF was detected in the vesicular membranes of endothelial cells in cerebral blood vessels 10 min after the infusion. Numerous immunoreactive small vesicles were also detected at the ependymal cells in the choroid plexus. Moreover, the bLF concentration in the CSF was significantly increased at 1-2 hr after the intravenous infusion of bLF (10 or 30 mg/kg). These findings clearly demonstrate that LF is possibly transported into the brain matter even in adult animals.

Enteric-formulated lactoferrin was more effectively transported into blood circulation from gastrointestinal tract in adult rats.

We have previously demonstrated that intestinally infused bovine lactoferrin (bLF) is transported into the blood circulation via the lymphatic pathway, not via the portal circulation. Therefore, in the present study, we further investigated whether intragastrically infused enteric-formulated bLF (EF-bLF) was more efficiently absorbed than bLF from the intestine in adult rats. The rats were randomly divided into three groups: 30 and 300 mg kg(-1) non-enteric-formulated bLF (non-EF-bLF) groups and a 30 mg kg(-1) EF-bLF group. Thoracic lymph was collected from a thoracic lymph duct under general anaesthesia. Bovine lactoferrin was infused into the stomach or duodenal lumen via a needle for a period of over 1 min in a volume of 1 ml kg(-1). The bLF transported into the lymph was assayed quantitatively by double-antibody enzyme-linked immunosorbent assay (ELISA). Following the intragastric administration of bLF, the three groups showed almost the same lymph flow, but the bLF concentration in the lymph fluid in the EF-bLF group increased significantly and peaked 3 h after administration. With intraduodenal administration, the bLF concentration in the lymph fluid of the higher non-EF-bLF group was significantly higher than those of the other groups. The amount of absorbed bLF in the EF-bLF group was, however, about 10 times higher than that in the lower non-EF-bLF group, when it was administered intragastrically. These data show that enteric-formulated bLF is less susceptible to gastric pepsin and is more efficiently absorbed from the intestine than is non-enteric-formulated bLF.

Suppressive effects of milk-derived lactoferrin on psychological stress in adult rats.

Lactoferrin (LF) is known as an iron-binding glycoprotein. It has been shown that bovine LF (bLF) is transported into cerebrospinal fluid via blood although its physiological effects in the central nervous system (CNS) are still unclear. In this study, a suppressive effect of bLF on psychological distress was investigated in adult rats. Intraperitoneal injection of bLF (100 mg/kg) reduced stressful behaviors in a conditioned fear-induced freezing test and an elevated plus-maze test. Interestingly, the suppressive effect of bLF was enhanced by pretreatment with electric foot-shock (FS). This suppressive effect of bLF in the elevated plus-maze test was reversed by pretreatment with naloxone, an opioid receptor antagonist, at a dose of 1 mg/kg (ip). N(omega)-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase (NOS) inhibitor, also blocked the suppressive effect of bLF and foot-shock. In addition, combined application of a low dose of bLF (30 mg/kg, ip) and l-arginine (30 and 100 mg/kg, ip) showed significant potentiated effects on psychological stress. These results suggest that bLF has suppressive effects on psychological distress, especially under the condition of moderate stress. Furthermore, it is suggested that bLF possibly activates an endogenous opioidergic system via nitric oxide synthase activation.