In vivo fluorometric assessment of cyclosporine on mitochondrial function during myocardial ischemia and reperfusion.

Abstract

Cyclosporine A (CsA) limits myocardial reperfusion injury and preserves mitochondrial integrity, but its influence on mitochondrial function has not been described in vivo. Auto-fluorescence of mitochondrial nicotinamide adenine dinucleotide and flavin adenine dinucleotide correlate with mitochondrial dysfunction. We hypothesized that CsA limits mitochondrial dysfunction and that fluorometry can quantify this influence. Seventeen rabbits were studied: untreated (UnT, n = 7), CsA preinfarction (CsAp, n = 6), and CsA on reperfusion (CsAr, n = 4). Animals underwent 30 minutes of myocardial ischemia and 3 hours reperfusion. Infarct size was determined by staining. Nicotinamide adenine dinucleotide and flavin adenine dinucleotide fluorescence was continually measured in the risk area. The redox ratio was calculated [flavin adenine dinucleotide(f)/(flavin adenine dinucleotide(f) + nicotinamide adenine dinucleotide(f))]. Electron microscopy evaluated mitochondria morphology. The infarct size by group was 39.1% +/- 1.7% in CsAp, 39.1% +/- 1.7% in CsAr, and 53.4% +/- 1.9% in UnT (p < 0.001). During ischemia, the CsAp group demonstrated less hypoxic reduction, with the redox ratio decreasing to 75.6% +/- 4.1% of baseline. The UnT and CsAr groups deceased to 67.1% +/- 4.0% and 67.2% +/- 3.6%, respectively (p < 0.005). During reperfusion the UnT group redox ratio increased to 1.59 +/- 0.04 times baseline. This increase was blunted in the CsAp (1.17 +/- 0.04, p = 0.026) and CsAr (1.35 +/- 0.02, p = 0.056) groups. Electron microscopy revealed reduced mitochondrial disruption in CsAp (19.7% +/- 7.6%) and CsAr (18.1% +/- 7.1%) rabbits compared with UnT (53.3% +/- 12.5%). Fluorometric spectroscopy can be used in vivo to quantitatively assess the time course of CsA's influence on the mitochondrial dysfunction associated with myocardial ischemia and reperfusion.