Figure 3. Distinct ion dependency of β amino acid uptake in PAT1- and TauT-expressing oocytes.

A, [³H]β-alanine (10 μm) uptake was measured into PAT1 cRNA-injected oocytes at pH 5.5 in the presence of NaCl or in Na⁺-free (–Na⁺) or Cl⁻-free (–Cl⁻) conditions, and at pH 7.4 under Na⁺-free (–Na⁺) conditions. Uptake in water-injected oocytes was subtracted from that in cRNA-injected oocytes to give PAT1-specific uptake. Data are mean ±s.e.m. (n= 17–18). NS, P > 0.05; ***, P < 0.001; all versus pH 5.5 –Na⁺. B,[³H]β-alanine (2 μm) uptake was measured into TauT cRNA-injected oocytes at pH 7.4 in the presence of NaCl or in Na⁺-free (–Na⁺) or Cl⁻-free (–Cl⁻) conditions, or at pH 5.5 in the presence of NaCl. Uptake in water-injected oocytes was subtracted from that in cRNA-injected oocytes to give TauT-specific uptake. Data are mean ±s.e.m. (n= 9–10). NS, P > 0.05; ***, P < 0.001; all versus pH 7.4 NaCl.