Fig. 2.

Impaired mitochondrial respiration in the PINK1^−/− striatum. (A) Representative oxygraphs of striatal mitochondria preparations for complex I, complex II and complex III/IV at 3–4 months of age. After injection of limiting amounts of ADP (indicated by arrows) state 3 was measured. After exhaustion of ADP, O₂ consumption slowed down representing state 4 of respiration. (B) State 3 respiratory activity was reduced for both complex I (n = 6) and complex II (n = 9) in PINK1^−/− mice. (C) State 4 respiratory activity was reduced for complex I in PINK1^−/− mice (n = 6) (*, P < 0.05). (D) Unchanged levels of complex I, complex II and complex III in the striatum at 3–4 months as measured by western blot. (E) Enzymatic activity of aconitase (acon.), malate dehydrogenase (MDH), cytochrome c oxidase (CxIV) and glucose-6-phosphate kinase (G6PK) measured from striatal lysates are shown as normalized to the citrate synthase activity. Aconitase activity was significantly lower in the PINK1^−/− striatum (**, P < 0.005, n = 6), whereas other mitochondrial enzyme activities were unaffected. (F) Striatal ATP concentrations are similar in the striatum of PINK1^−/− and wild-type mice.