Characteristic distribution patterns of Na
-channels and Na
-exchangers. Amiloride-FL staining, WFM, S9 to S10B, A, B, C: representative grey-scale images, A´, B´, C´: corresponding pseudocolour images. Amiloride-sensitive Na+-transporters are distributed in an anteroposterior gradient within the NC group. Usually, high concentrations were found in anterior NC with declining concentrations in posterior direction (see scale bar), the NC adjacent to the anterodorsal region of the Ooc (asterisk) having the lowest concentation. In D the characteristic distribution patterns are summarized, high concentrations of Na+-transporters are shown in purple (staining in Ooc is not considered). For abbreviations, see Figure 1.