Figure 5
Effect of superoxide plus palmitate in the absence (black triangle) or presence (open cycle) of GDP on basal proton conductance (black square) of red gastrocnemius muscle mitochondria isolated from thermoneutral controls (TN), cold-acclimated (CA), hypothyroid (hypo) or T 3 -treated ducklings. Proton conductance was assessed by simultaneous measurement of membrane potential and oxygen consumption. Superoxide generation was obtained by addition of 50 μM xanthine (X) and 8 mU/3.5 mL xanthine oxidase (XO). When observed, increase in proton conductance was reversed by 1 mM GDP. All measurements were conducted with 5 mM succinate as substrate, 5 μM rotenone, 1 μg/mL oligomycin, 65 ng/mL nigericin, 0.3% FAF-BSA and 25 μM palmitate. Mitochondria from CA or T3-treated ducklings showed a much larger GDP sensitive XXO-activated proton conductance compared with TN or hypothyroid birds in which XXO had no major effect. Data are means ± S.E.M. from 5 to 11 independent determinations.