Fig. 1.

Aldosterone induces apical membrane and total Na⁺/H⁺ exchange (NHE)3, but not total NHE2. A: unidirectional ²²Na uptakes were used to measure apical membrane NHE activities as described in materials and methods following treatment with 1 nM aldosterone (Aldo) for varying times. Fluxes shown are means ± SE for 6 separate experiments. *P < 0.05, +P < 0.01 compared with 0 time by analysis of variance using a Bonferroni correction. B: aldosterone increased surface and total expression of NHE3 but did not affect total cellular expression of NHE2. Cells were treated with 1 nM aldosterone, and NHE expression was determined in cell lysates (total) and apical surface (apical biotinyl) NHE3 determined using apical surface biotinylation. C: aldosterone stimulates a concentration-related increase in total NHE3 expression. Cells were harvested for determination after 48-h treatment. Images shown are representative of those of 6 separate experiments for B and C. *P < 0.05, +P < 0.01, ++P < 0.001 compared with no treatment within this set (B or C) by analysis of variance using a Bonferroni correction.