Transport of bovine serum albumin across rat jejunum: role of the enteric nervous system

Abstract

To assess the mechanisms for movement of antigenically intact macromolecules across small intestinal mucosa, transport kinetics of bovine serum albumin (BSA) uptake and the effect of neural and metabolic inhibition were examined in stripped short-circuited rat jejunum. The mucosa was exposed to BSA, and, after a 50-min equilibration, mucosal-to-serosal movement of immunologically intact BSA was determined by enzyme-linked immunosorbent assay and total BSA by radiolabeled 125I-BSA. Intact BSA uptake demonstrated saturable kinetics. Immunologically intact BSA crossed the intestinal mucosa as 4.5% of total 125I-BSA flux. Colchicine and 4 degrees C significantly reduced uptake of immunologically intact BSA. NaF significantly reduced uptake of immunologically intact BSA and 125I-BSA. Treatment with tetrodotoxin significantly reduced intact BSA uptake, but did not significantly alter total BSA uptake. The muscarinic cholinoceptor antagonist atropine also significantly inhibited transport of intact BSA, whereas the nicotinic cholinoceptor antagonist hexamethonium had no effect. These findings indicate that transport of intact macromolecules across small intestinal mucosa is a saturable energy-dependent process that utilizes the microtubular network and is regulated by the enteric nervous system primarily through cholinergic nerves acting on muscarinic receptors.