Electrophysiological characterization of chloride secretion across the jejunum and colon of pigs as affected by age and weaning

Hypersecretion of chloride can cause diarrhea, a disease frequently occurring in young pigs, particularly around weaning. We investigated the contribution of different channels to intestinal Cl− secretion as influenced by age and weaning. Jejunal and colonic epithelia from 4-month-old pigs and 4-week-old piglets were incubated in Ussing chambers and stimulated by carbachol and forskolin. Changes in short-circuit currents were taken as measure of electrogenic net Cl− secretion. DIDS or NPPB served to inhibit Ca-activated Cl−-channels and outwardly rectifying Cl−-channels (ORCC) or cystic fibrosis transmembrane regulator (CFTR), respectively. Depolarizing the basolateral membrane allowed to examine the influence of K+-channels on Cl− secretion. Forskolin-stimulated Cl− secretion was mediated by CFTR. ORCC were not involved. Carbachol-induced Cl− secretion could be ascribed to an enhanced driving force due to the opening of K+-channels, whereas Ca-dependent Cl− channels seemed not to be involved. In jejunum, piglets showed higher Cl− secretion than pigs. Two days after weaning forskolin induced an I sc overshoot and a faster increase in G t. In colon, Cl− secretion was neither influenced by age nor by weaning. The data suggest a disposition of porcine jejunum for a higher Cl− secretion in young and freshly weaned piglets, which might be a natural defense mechanism as well as a predisposing factor for diarrhea.