AJP - Cell Physiology, Vol 260, Issue 4 C750-C755, Copyright © 1991 by American Physiological Society
Brain natriuretic peptide stimulates K and Cl secretion across porcine distal colon epithelium
T. R. Traynor and S. M. O'Grady
Department of Veterinary Biology, University of Minnesota, St. Paul 55108.
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 microA/cm2) in short-circuit current (Isc).
These increases in Isc 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 Isc. 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.
