Respiratory properties of skeletal muscle mitochondria.

<p>A: Oxygen consumption by mitochondria isolated from mice 8–9 months following treatment with tamoxifen. Values are means ± SEM (n = 4). “State 3” indicates respiration rates during ATP synthesis, “State 4” is in the presence oligomycin to inhibit ATP synthesis, and “uncoupled” is in the presence of carbonyl cyanide p-[trifluoromethoxy]phenylhydrazone to measure maximal respiration rates. The uncoupled rate with α-ketoglutarate is low because the enzyme was depleted of ADP, its allosteric activator; additional data (not shown) demonstrated that addition of ADP increased the uncoupled rate. B: Cytochrome content: values are means ± SEM (n = 5). C: Respiration of mitochondria treated with NaCN. NaCN (15 µM) was added to control mitochondria to mimic the 40% reduction in cytochrome oxidase observed in mitochondria from KO compared to control mice. Respiration, measured in the presence of ketoglutarate, pyruvate+malate, and succinate+rotenone, was compared with that of untreated mitochondria from KO mice. D: Abundance of subunits of the five respiratory chain complexes in mitochondria from KO (n = 3) relative to HF control (n = 4) mice. Western blotting was used to detect subunits of complexes I (NDUFB8), II (30 kDa subunit), III (core protein 2), IV (subunit 1) and V (alpha subunit), employing primary antibodies obtained from Mitosciences. The antigen targets represent labile subunits that are degraded when not assembled into the appropriate complex and thus are representative of the abundance of the fully assembled complexes. Mitochondria were isolated from two groups of mice 8–9 months and 3–4 months following treatment with tamoxifen. Statistical significance in unpaired <i>t</i>-tests is indicated by *p>0.05 or **p<0.005; for p values of marginal significance actual values are shown.