Fig. 4. (A) A comparison of ammonia flux rates (JAmm, over 6 h) between epithelia exposed under symmetrical conditions (L-15 apical/L-15 basolateral) to either basolateral manipulations (basolateral-to-apical fluxes; open columns, data from Fig. 3) or apical manipulations (apical-to-basolateral fluxes; filled columns) of pH at total ammonia (TAmm)=650 µmol l–1 in series 3. The overall effects of pH and of direction were significant (P<0.05), although there were no significant differences with respect to direction at the same pH values. (B) Mean pH gradients and (C) mean PNH3 gradients associated with these treatments. In B and C, there were no significant differences (P>0.05) attributable to direction, although the overall effects of pH were highly significant (P<0.0001). Values are means +1 S.E.M. (N=6 per group for all basolateral manipulations and N=5–6 per group for all apical manipulations). Significant differences between specific groups within a treatment (pHBl effect) are denoted by different letters. 1 nmHg=0.133 Pa.
