Figure 5.

Specific binding of [8-³H]IMP to neutrophils. [8-³H]IMP was prepared by biogenic synthesis. Structure of IMP with the ³H label position 8 is indicated in the Upper Right Inset. Isolated human neutrophils (8 × 10⁶ cells in 0.4 ml) were incubated with [8-³H]IMP (0–500 nM) at 4°C for 120 min in the presence or absence of a 1000-fold excess of unlabeled IMP. (Lower Right Inset) Scatchard analysis for [8-³H]IMP binding. The K_d is 251.3 ± 27.7 nM and the B_max is 4.5 ± 0.2 pmol/mg of protein (n = 4). (Upper Left Inset) Competition of unlabeled IMP (●) or adenosine (○) for specific [³H]IMP (200 nM) binding to intact neutrophils (n = 4). The IC₅₀ value for unlabeled IMP was ≈122 nM and that for adenosine was ≈19.2 μM (n = 4).