TRANSPORT OF BOVINE SERUM-ALBUMIN ACROSS RAT JEJUNUM - ROLE OF THE ENTERIC NERVOUS-SYSTEM

To assess the mechanisms for movement of antigenically intact macromol ecules across small intestinal mucosa, transport kinetics of bovine se rum albumin (BSA) uptake and the effect of neural and metabolic inhibi tion were examined in stripped short-circuited rat jejunum. The mucosa was exposed to BSA, and, after a 50-min equilibration, mucosal-to-ser osal movement of immunologically intact BSA was determined by enzyme-l inked immunosorbent assay and total BSA by radiolabeled I-125-BSA. Int act BSA uptake demonstrated saturable kinetics. Immunoiogically intact BSA crossed the intestinal mucosa as 4.5% of total I-125-BSA flux. Co lchicine and 4 degrees C significantly reduced uptake of immunological ly intact BSA. NaF significantly reduced uptake of immunologically int act BSA and I-125-BSA. Treatment with tetrodotoxin significantly reduc ed 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 net work and is regulated by the enteric nervous system primarily through cholinergic nerves acting on muscarinic receptors.