FIGURE 2.

Stability and time-dependent localization of per os administered Aβ peptides in the murine gastrointestinal tract. (A) TAMRA-labeled Aβ peptide was incubated in two different concentrations [high (H): 0.025 μM; low (L): 0.005 μM] with PBS-diluted gastric content of wild type mice for 2 h at 37°C. Solvent of the peptide was used as a negative control (–). Additionally, samples with PBS instead of chyme were incubated as described (buffer). Proteins were separated on PAA gel and transferred to nitrocellulose. Detection of Aβ-dependent signal was conducted by antibody 6E10 (upper panel) or by fluorescence (lower panel). The arrow indicates a cross reactivity only occurring in chyme. (B) To assess the passage of orally administered Aβ peptides, wild type or 5xFAD mice were fed with 10 μg of TAMRA-labeled Aβ peptides and sacrificed at indicated time points. TAMRA-dependent fluorescence was determined in the chyme of 2 cm gut sections numbered from 1 (oral end = stomach) to 12 (rectal section). Values are presented as measured difference between the TAMRA-Aβ-treated animals and solvent-treated control animals (one animal per time point, technical duplicates).