Fig. 1. (A) Effects of apical and basolateral pH shifts on the transepithelial secretory (positive sign) K⁺ current. K32, standard saline (see Materials and methods); a, apical variations; b, basolateral variations. (B) Reduction in active K⁺ transport induced by 5 mmol l^–1 basolateral Ba²⁺ and basolateral/apical acidification in the absence of Ba²⁺.