Kinetics of mitochondrial flavoprotein and pyridine nucleotide in perfused heart.

CHANCE, BWTON, IRVING A. SALKOVITZ, AND ARISTID G. B. ~VACH. Kinetics of mitochondrial javoprotein and pyridine nucleotide in perfused heart. Am. J. Physiol. 213(l): 207-218. 1972.-Fast activation of mitochondrial electron transport can identify the nature and magnitude of their metabolic energy load. Flash photolysis activation of CO-inhibited cytochrome oxidase in the presence of oxygen initiates oxidation of reduced pyridine nucleotide (PN) and flavoprotein (Fp) and the rate of the response is high at high ADP and Ca 2f levels. The fractional extent of the photolysis response of PN and Fp indicates the fraction of the total mitochondrial population containing cytochrome a&O to which oxygen has diffused at the time of the photolysis flash. This fraction is 4X.5 for PN and Fp responses and is considered to be a useful indicator of the effectiveness of oxygen diffusion in the tissue. Such a rapid response ( <O. 1 set) is not observed in vitro in the presence of ADP + Pi, extramitochondrial Ca2+ concentrations are required. Techniques for the rapid perturbation of the physiological and biochemical states of intact tissues are reviewed and the method of flash photolysis of the mitochondrial cytochrome as-CO compound in the presence of oxygen is described, together with the recording of the oxidation-reduction states of mitochondn’al PN and Fp.