Figure 7. Effect of cADPR on whole-cell currents in neutrophil granulocytes in the presence of 1 μM intracellular Ca²⁺.

(A) The pipette solution that contained nominally 10 μM cADPR was prepared from a cADPR stock solution considerably contaminated with ADPR, as shown with HPLC (inset). Inward currents developing during infusion of contaminated cADPR were blocked by NMDG present in the bath during time periods indicated by horizontal bars. (B) In contrast with (A), the pipette solution was prepared from a cADPR stock solution incubated with nucleotide pyrophosphatase (2.7 units/ml, 20 min, 37 °C), resulting in the complete conversion of ADPR into AMP (inset). ADPR was then added to the pipette solution at a subthreshold concentration (0.1 μM). The absence of currents under these conditions was confirmed in three further experiments. (C) To check for the effects of AMP, AMP (5 μM) was added to a pipette solution containing ADPR (5 μM). AMP did not prevent or noticeably alter ADPR-induced currents in three further experiments.