Fig. 6.

CBD is a competitive inhibitor at the ENT1 transporter in EOC-20 cells. (A) Cells were preincubated for 30 min with indicated concentrations of CBD before incubation with 1 nM [³H]NBMPR for 30 min at 4°C or 37°C. Nonspecific binding, determined in the presence of 10 μM nitrobenzylthioguanosine, was subtracted; the combined results of three experiments are shown. IC₅₀ values, derived from the solution of a single-site competition equation in individual experiments (each n = 3), were used to calculate the dissociation constant for CBD. (B) Kinetics of [³H]NBMPR binding. EOC-20 cells were preincubated with vehicle or 500 nM CBD before [³H]NBMPR was added for a 30-min incubation at 37°C. Nonspecific binding was subtracted. Shown is one representative experiment of three; the lines represent the solution of the one-site binding equation (n = 3). A Scatchard plot of the data is shown (Inset).