FIG. 2.

Sodium and chloride ion dependences of [¹⁴C]faropenem uptake by Xenopus oocytes expressing mouse Npt1. (A) Uptake of [¹⁴C]faropenem was measured in the presence or absence of sodium ions. In the sodium ion-free experiment, sodium ions were replaced with potassium ions. (B) Uptake of [¹⁴C]faropenem was measured in medium containing various concentrations of chloride ions. The chloride ion concentration was adjusted by replacing sodium chloride with sodium gluconate to give a constant sodium ion concentration. Closed and open symbols represent the results obtained with Xenopus oocytes injected with mouse Npt1 cRNA and water, respectively. Data are expressed as the means ± SDs for six to eight uptake measurements.