Figure 7. Influence on preconditioning by conditions affecting inflow of Ca²⁺ and/or insulin secretion (A–B), HIF1α (C) and AMPK (D).

In A and B preconditioning was performed with diazoxide (dz) in the presence or absence of tolbutamide (100 µmol/l) or potassium (30 mmol/l). Also tested were effects of nifedipine (10 µmol/l) and cooling (28°C). A depicts insulin secreted to the culture medium expressed as % of no addition. B depicts islet insulin contents measured after 5.5 h of hypoxia followed by re-oxygenation. Incremental effects are shown as % of hypoxia only. Absolute values for Fig. 7A and B are shown in Text S1. Mean ± SEM of four experiments. C depicts effects of preconditioning with diazoxide (dz) on HIF1α protein (Western blot) before hypoxia and after 5.5 h of normoxia/hypoxia. Mean ± SEM of nine experiments, *P<0.05 vs. no previous diazoxide. D depicts effects of preconditioning with diazoxide (dz) by Western blotting on the ratio of AMPKα to phosphorylated AMPKα (p-AMPKα) in sequence to hypoxia and after re-oxygenation. Mean ± SEM of three experiments, *P<0.05 vs. no previous diazoxide. Representative blots are shown. Red columns: normoxia; blue columns: hypoxia.