Figure 4.

IC₅₀ determination for the inhibition of OAT2-mediated cGMP uptake by furosemide and bumetanide. In HEK293 cells stably transfected with OAT2 or empty vector, intracellular cGMP accumulation was determined after coincubation with 10 μM cGMP (0.1 μM [³H]cGMP + 9.9 μM unlabeled cGMP) and 1–1000 μM furosemide (a) or 10–1000 μM bumetanide (b), respectively, for 5 min at 37°C. The furosemide and bumetanide concentrations causing half-maximal inhibitory effect (IC₅₀) on cGMP accumulation in OAT2 expressing cells were calculated. Data are presented as mean ± SEM. n _furosemide = 2–4; n _bumetanide = 2.