Macromolecular Absorption

Abstract

The immature small intestine of neonatal mammals is permeable to gamma globulins as a source of passive immunity. Allegedly, macromolecular absorption ceases when the epithelial cell membrane matures. However, some evidence exists that adult animals retain a limited capacity to transport antigenic and biologically active quantities of large molecules. In this study, the mechanism of absorption of the tracer protein, horseradish peroxidase (HRP), was tested in neonatal and adult rat gut sacs. Transport into serosal fluid was quantitated by enzymatic assay and monitored morphologically by histochemical techniques. A greater transport of HRP was noted in the adult jejunum compared to adult ileum and neonatal intestine. Morphologically, the uptake mechanism in adult intestine was similar to the endocytosis previously reported in neonatal animals Like other endocytotic processes, HRP uptake in adult rats is an energy-dependent process as determined by metabolic inhibitors and temperature-controlled studies. An understanding of the mechanism whereby macromolecules are bound to intestinal membranes and engulfed by them is necessary before the action of physiologic macromolecules such as enterotoxins can be appreciated.

Intestinal Transport of Antibodies in the Newborn Rat

“…This small amount of tracer seen in the dense bodies probably reflects a nonselective uptake similar to the uptake observed in cells of the adult (Cardell et al, 1967 ;Casley-Smith, 1967 ;Cornell et al ., 1971) . Quantitative estimates (Warshaw et al ., 1971 ;Walker et al ., 1972) indicate that transport of intact protein to the circulation is extremely small in the adult compared to the amount of antibody transport in the neonate (Halliday, 1955 b ;Rodewald, 1970) .…”

Transport of β-lactoglobulin and α-lactalbumin in enterocyte-like Caco-2 cells

“…Afin de quantifier les différentes voies de transport des protéines à travers l'épithélium intestinal, nous avons étudié le transport de la p -lactoglobuline et de l â -lactalbumine, marquées au !4C, à travers des cellules Caco-2 cultivées en monocouches sur des filtres perméables. Après addition de la p-lactoglobuline ou de 1'(x-lactaibumine (0,25 à 3 mglml) dans le compartiment apical, le (Danforth and Moore, 1959;Walker et al, 1972;Warshaw et al, 1974). Different functions are associated with this mechanism, including passive immunity (Walker, 1981;Gardner, 1988), ligand transport (Papiz et al, 1986;Brown et al, 1988) and various metabolic regulation mechanisms (Gardner, 1988;Lee et al, 1990; Sanderson and Walker, 1993).…”

“…Different functions are associated with this mechanism, including passive immunity (Walker, 1981;Gardner, 1988), ligand transport (Papiz et al, 1986;Brown et al, 1988) and various metabolic regulation mechanisms (Gardner, 1988;Lee et al, 1990; Sanderson and Walker, 1993). Results obtained with different proteins show that protein transport through the intestinal epithelium proceeds by a major transcellular degradative pathway together with a minor intact transport route (Cornell et al, 1971;Walker et al, 1972;Walker, 1981;Stern and Walker, 1984;Gardner, 1988;Marcon-Genty ef al, 1989;Hughson and Hopkins, 1990; Le Bivic et al, 1990;Matter et al, 1990;Heymann et al, 1990;Tome, 1992, 1994;Heyman and Desjeux, 1992 (Walker, 1981;Gardner, 1988 (Shen et al, 1992).…”

Permeability of milk protein antigens across the intestinal epithelium in vitro

“…(Fig. 4) Miranda & Pelissier, 1981 The capacity for a-La digestion in the small intestine also seemed very large, whereas, ¡3-Lg appeared the most resistant to luminal digestion (Fushiki et al, 1986; (Cornell et al, 1971;Walker et al, 1972). In the present study, this total uptake, evaluated as radiolabelled-protein equivalent transfer, exhibited differential kinetics for fi-Lg, in comparison to a-La and p-cas.…”

“…It is generally accepted that proteins or their antigenic fragments, which resist degradation by proteolytic enzymes of the gastrointestinal tract and cross the intestinal mucosa intact, are able to stimulate immunocomponent cells in the lamina propria (Baird et al, 1987;Fiillstr6m et al, 1984;Cornell et al, 1971;Heyman et al, 1982;Koritz et al, 1987;Stern & Walker, 1984;Walker et al, 1972). For this reason, it is important to know the proportion of antigenic protein that remains present during digestion by gastrointestinal enzymes and during their intestinal transepithelial passage.…”