FIGURE 3.

Inhibition of endogenous apyrase increased extracellular levels of ATP and stimulated [Ca²⁺]_i oscillations and insulin secretion. (a) Addition of the selective ecto‐ATP‐nucleotidase inhibitor ARL67156 (50 µM) to pre‐washed (1 + 2) MIN6 and (Bours et al., 2006) mouse primary β‐cells started [Ca²⁺]_i oscillations (concentrations as indicated). Representative (ai) single and (aii) averaged [Ca²⁺]_i traces, recorded with the Ca²⁺ indicator Fluo‐4. Numbers of detected high‐intensity [Ca²⁺]_i events per 60 s interval in (aiii+iv) MIN6 and (av) mouse primary β‐cells. (bi) Insulin and (bii) ATP levels, as determined from the supernatant of MIN6 cells in the presence of ARL67156 in different concentrations. Shown are averages of n = 50 MIN6 and n = 30 mouse primary β‐cells. Imaging was performed in the presence of 11 mM glucose (MIN6 cells) and 5 mM glucose (mouse primary β‐cells). Washes are indicated by ▼. Insulin and ATP measurements were performed in quadruplicate (ANOVA. *p < 0.05, **p < 0.01, ns = not significant = p > 0.05, with repeated measures as necessary). Error bars present SD