Effects of Ca2+ on the inhibition by IP6 of the ATP-independent release from DG-permeabilized cells. The cells were permeabilized for 4 min with DG buffer, incubated two times for 2 min with the buffer without DG, and then stimulated with Ca2+ (0–500 μM) buffer (Ca2+-HEEDTA buffer) for 1.5 min in the absence of MgATP. MgATP (5 mM) was only added during the permeabilization and the incubation for the first 2 min. IP6 (10−4 M) was added during the incubation for the last 2 min and the subsequent stimulation. The amounts of released CA are expressed as the percentage of total cellular content. Amount of CA released in the absence of Ca2+ was measured for each group, and the mean value for each group was subtracted from each evoked release. Data are the mean ± SEM of at least eight determinations from individual wells. ∗, P < 0.01; ∗∗, P < 0.001, when compared with control.