Optical studies of tissue mitochondrial redox in isolated perfused rat lungs

Through the monitoring of the auto-fluorescent mitochondrial metabolic coenzymes, NADH (Nicotinamide Adenine Dinucleotide) and FAD (Flavoprotein Adenine Dinucleotide), the redox state of metabolism can be probed in real time in many intact organs, but its use has not been fully developed in lungs. The ratio of these fluorophores, (NADH/FAD), referred to as the mitochondrial redox ratio (RR), can be used as a quantitative metabolic marker of tissue. We have designed a fluorometer that can be used to monitor lung surface NADH and FAD fluorescence in isolated perfused lungs. Surface fluorescence NADH and FAD signals were acquired in the absence (control) and presence of pentachlorophenol (PCP), rotenone, and potassium cyanide (KCN). Rotenone, an inhibitor of complex I, increased RR by 18%, predominantly due to an increase in NADH signal. KCN, an inhibitor of complex IV reduced the chain and resulted in an increase of 33% in RR, as a result of 23% increase in NADH and 8% in FAD . PCP, an uncoupler which oxidizes the respiratory chain, decreased RR by 18% as a result of 14% decrease in NADH signal and 4% increase in FAD signal. These results demonstrate the ability of surface fluorometry to detect changes in lung tissue mitochondrial redox state in isolated perfused lungs.