Electrical charge on protein regulates its absorption from the rat small intestine

Abstract

The effect of the electrical charge on the intestinal absorption of a protein was studied in normal adult rats. Chicken egg lysozyme (Lyz), a basic protein with a molecular weight of 14,300, was selected and several techniques for chemical modification were applied. Then the intestinal absorption of Lyz derivatives was evaluated by measuring the radioactivity in plasma and tissues, after the administration of an (111)In-labeled derivative to an in situ closed loop of the jejunum. After the administration of (111)In-Lyz, the level of radioactivity in plasma was comparable with the lytic activity of Lyz, supporting the fact that the radioactivity represents intact Lyz. (111)In-cationized Lyz showed a 2-3 times higher level of radioactivity in plasma, whereas the radioactivity of (111)In-anionized Lyz was much lower. The absorption rate of (111)In-Lyz derivatives calculated by a deconvolution method was correlated for the strength of their positive net charge. A similar relationship was observed using superoxide dismutase. These findings indicate that the intestinal absorption of a protein is, at least partially, determined by its electrical charge.

Immunohistochemical Study on the Secretory Host Defense System of Bactericidal Peptides in Rat Digestive Organs

“…In lysozyme absorption, however, megalin might not be important and the cationic charge of lysozyme might be important in the rat small intestine [36]. In general, the intestinal epithelial surface is anionically charged, and intestinal absorption of a protein is, at least partially, determined by its cationic charge [26,36]. Lysozyme and defensin molecules are strongly cationic charged [6].…”

Polymeric Immunoglobulin Receptor in Intestinal Immune Defense against the Lumen-Dwelling Protozoan ParasiteGiardia

“…Alternatively, passive diffusion across the normal epithelium may be sufficient to account for the substantial fecal IgA output in pIgR-deficient mice, a notion supported by the observation that a significant fraction of orally administered protein Ags can be found in the circulation in intact form under normal conditions (59,60). Such apparent physiologic permeability in the normal intestine for intact proteins may be explained by microulceration or physiologically relevant residual epithelial permeability (61). The occurrence of significant passive diffusion of IgA across the intestinal epithelium in pIgR-deficient mice is also consistent with our observation that the ratios of circulating Ig to fecal Ig output were comparable for IgA and IgG in these mice, as adult mice express only low levels of high-capacity intestinal IgG transporters (62).…”

Activation of a passive, mesoporous silica nanoparticle layer through attachment of bacterially-derived carbon-quantum-dots for protection and functional enhancement of probiotics

“…2 ). Considering that intestinal epithelial cells also possess a negatively charged surface [ 29 ], B. infantis encapsulated in a shell with attached E. coli derived CQDs will experience less electrostatic double-layer repulsion and adhere better through attractive Lifshitz-Van der Waals attraction to intestinal epithelial cell layers than when L. acidophilus derived CQDs are employed to activate the shell. Data thus show ( Fig.…”