REVERSIBLE INCREASE IN TIGHT JUNCTION PERMEABILITY TO MACROMOLECULES IN RAT ILEAL MUCOSA IN-VITRO BY SODIUM CAPRATE, A CONSTITUENT OF MILK-FAT

Intestinal tight junction function is thought to be of importance in t he pathogenesis of various diseases. The regulation of uptake of macro molecules via the tight junctions is largely unknown. Effects of lumin al sodium caprate (10 mM), a dairy product constituent, and cytochalas in B (30 mu M), were studied in rat ileum in vitro in Ussing chambers. Both agents caused a reversible fall in potential difference and incr eased [Cr-51]EDTA permeability. In addition, sodium caprate induced in creased permeability to polysucrose (15,000 daltons) and opening of th e tight junctions as visualized by transmission electron microscopy. D ose-response patterns suggested mainly dose-dependent differences betw een the agents. Confocal laser scanning microscopy suggested paracellu lar permeation of polysucrose. Luminal sodium caprate, a food constitu ent, can increase tight junction permeability, allowing passage of mac romolecules, without affecting epithelial viability. Increased permeab ility to medium-sized molecules does not necessarily coincide with inc reased paracellular uptake of protein-sized molecules.