Table 1. Assessment of mitochondrial respiratory chain function.
| Substrate/electron donor | Site(s) of electron input | Method | Results | ||
| AER | AER/IL | p-value | |||
| pyruvate/malate | Complex I (NADH:ubiquinone oxidoreductase) | HRR | 8.3 (0.6) | 7.0 (0.4) | 0.074 |
| pyruvate/malate/succinate | Complex I+II | HRR | 10.7 (0.8) | 12.2 (0.8) | 0.243 |
| succinate | Complex II (succinate:ubiquinone oxidoreductase) | HRR | 6.1 (0.7) | 7.8 (0.5) | 0.080 |
| decylubiquinol | Complex III (ubiquinol:ferricytochrome c oxidoreductase) | SP | 8.5 (0.7) | 8.1 (0.3) | 0.652 |
| ascorbate/TMPD | Complex IV (cytochrome c oxidase) | HRR | 22.2 (1.6) | 16.3 (1.5 | 0.024 |
| palmitoylcarnitine/malate | Complex I+Electron transfer flavoprotein-ubiquinone oxidoreductase | HRR | 2.9 (0.3) | 2.6 (0.2) | 0.434 |
Rat hearts were aerobically perfused with/without Intralipid (1%). Complex I, complex II, and complex IV function was measured polarographically by monitoring oxygen consumption in presence of specific substrates and ADP in saponin-skinned cardiac fibers using high-resolution respirometry (HRR). Complex III enzymatic activity was assayed spectrophotometrically (SP). The measured oxygen consumption (normalized to citrate synthase activity) is expressed as nmol O2*s−1/CS. Complex III activity is expressed as mOD*min−1/µg mitochondrial protein. Data are presented as mean (SEM). N = 6–10 in all groups.
Abbreviations:
AER, aerobically perfused hearts without treatment; AER/IL, aerobically perfused hearts exposed to Intralipid (1%); TMPD, tetramethyl-p-phenylene diamine, an artificial electron carrier which is reduced by ascorbate producing electrons that are transferred to cytochrome c; OD, optical density.