Effect of amiloride on potential difference across rectal mucosa in cystic fibrosis patients

This study investigated whether the altered epithelial cell function in cystic fibrosis (CF) concerns channels for passive diffusion of sodium across cell membranes. For this purpose, the potential difference (PD), which arises across the colonic mucosa from electrogenic sodium transport, was compared in CF and non-CF subjects, together with the effect on this PD from bathing the mucosa with the specific Na+ channel blocker, amiloride. The resting rectal mucosal PD did not differ significantly in the two groups. Amiloride caused a dose-dependent decrease in the PD (lumen negative to skin) in all subjects. The mean amiloride effect was less in the CF population at 10(-8), 10(-7), 10(-6), 10(-5), and 10(4) M amiloride. The decrease of transmucosal PD in CF patients was significantly less when compared with controls at 10(6) M and 10(-5) M and suggestive of a similar trend at 10(-4) M.