Figure 2: Effects of UCP2 overexpression and oxidative stress on mitochondrial respiration in INS-1 cells. UCP2 was induced in INS-1 cells (hUCP2 INS-1-r9, [3]) by 250 ng/mL doxycycline (+Dox) 2 days before oxidative stress and during stress period. (a) Immunoblotting showing UCP2 protein levels in noninduced (−Dox) versus induced (+Dox) INS-1 cells and nonstressed (−stress) versus stressed cells (+stress, 200 μM H2O2 for 10 min 3 days before analysis). Cytochrome oxidase (COX IV) is shown as control for inner mitochondrial protein. (b) O2 consumption measured on mitochondria isolated from INS-1 cells 3 days after-stress. Respiration was induced by 5 mM succinate (Succinate) followed by addition of 150 μM ADP (Succinate + ADP). (c) O2 consumption measured on intact INS-1 cells stimulated by 15 mM glucose (Glc), compared to basal respiration at 2.5 mM glucose (Basal). Data are means ± SE of 3 independent experiments expressed as nmol O2/min per 100 μg mitochondrial protein (b) or nmol O2/min per 106 cells (c) normalized to basal respiration of controls (no Dox, no stress). 𝑃 < 0 . 0 5   versus basal O2 consumption of corresponding condition.