Figure 3. Effects of inward NH₄⁺ gradients on pH-gradient stimulated Na⁺ uptake into BLMVs and LMVs.

Uptake of 0.1 mM ²²Na⁺ into BLMVs was assayed as described for Fig. 2 except that the concentration of Tris-Mes was either 25 or 100 mM in the equilibration media, and the concentration of Tris-Hepes in the respective incubation media was 25 or 100 mM. Uptake was determined in the presence of sucrose (control; □) or with isosmotic replacement of sucrose by 10 mM ammonium acetate () or 5 mM (NH₄)₂SO₄ (▪). Uptake of 0.1 mM ²²Na⁺ into LMVs was as described above with high (100 mM) buffer concentration except that the concentrations of ammonium acetate and (NH₄)₂SO₄ were 20 and 10 mM, respectively. Values are means ±s.e.m. of six determinations on two different BLMV and LMV preparations.