Figure 4.

Substrate dependence (a), phlorizin inhibition (b), and Na⁺ dependence (c) of the expressed [¹⁴C]β-d-Glc-IPM uptake by SAAT1. Xenopus oocytes were injected with 50 nl of water without or with 10 ng of SAAT1-cRNA and incubated for 5 days. In both types of oocytes initial uptake rates of [¹⁴C]β-d-Glc-IPM were measured after 30 min of incubation, and the expressed uptake rates were calculated. (a) The expressed [¹⁴C]β-d-Glc-IPM uptake measured in Ori buffer containing different concentrations of [¹⁴C]β-d-Glc-IPM. (b) The expressed uptake of 0.8 mM [¹⁴C]β-d-Glc-IPM is shown, which was measured in Ori buffer containing different concentrations of phlorizin. (c) The expressed uptake rate of 0.8 mM [¹⁴C]β-d-Glc-IPM measured in the presence of different sodium concentrations. Here sodium in the Ori buffer was replaced by tetramethylammonium.