Figure 7.

Effect of extracellular pH on organic cation uptake by human airway epithelial cells. ASP⁺ uptake was measured by exposing the cells to 10 μM ASP⁺ for 15 min at 37°C in an incubation medium adjusted to different pH levels. Control was calculated as the temperature-sensitive (saturable) uptake of ASP⁺. Results represent mean ± SEM (n = 3 or 4 experiments). *P < 0.05 versus control.