Porcine distal colon epithelium was mounted in Ussing chambers and bathed with porcine Ringer solution. The serosal addition of brain natriuretic peptide (BNP; 50 nM) or atriopeptin III (AP-III; 500 nM) produced significant increases (50-75 μA/cm2) in short-circuit current (I(sc)). These increases in I(sc) were not inhibited by pretreatment with tetrodotoxin (TTX) or 5,8,11,14-eicosatetraynoic acid (ETYA). Analysis of concentration-response relationships revealed that BNP was 5.8-fold more potent than AP-III in stimulating the I(sc). BNP and AP-III significantly increased the serosal-to-mucosal (S→M) Cl flux and reduced net Cl absorption by 38 and 41%, respectively. The BNP-stimulated S→M Cl flux was abolished when HCO3 was removed. In contrast, the vasoactive intestinal peptide (VIP)-stimulated S→M Cl flux was not affected by HCO3 replacement. In addition to their effects on Cl transport, BNP and AP-III increased net Rb secretion by 79 and 58%, respectively. BNP-stimulated Rb secretion was reduced by 76% after HCO3 replacement. These results indicate that natriuretic peptides stimulate K- and HCO3-dependent Cl secretion which is not present under basal conditions or after VIP stimulation. The difference in potency between BNP and AP-III suggests that ANP-B receptors may mediate their effects on ion transport in the porcine colon.
- Atrial natriuretic factor-B receptor
- Atrial natriuretic peptide
- Intestinal ion transport
- Vasoactive intestinal peptide