A Time-Sharing Instrument for Direct Readout of Oxidation-Reduction States in Intracellular Compartments of Cardiac Tissue

Internal fluorochromes and chromophores afford the possibility of a continuous, nondestructive readout of biochemical information from complex systems such as intact organs. An instrument has been constructed which allows simultaneous observation of fluorescence emission from reduced pyridine nucleotides [NAD(P)H] and certain oxidized flavoproteins together with dual wavelength absorption measurements of cytochrome b. The instrument is applied to a preparation of perfused frog heart. The kinetic responses of the three parameters to oxygen, nitrogen, and 2-mM amytal are observed. Flavoprotein and cytochrome b show a delayed reduction in response to a transition from O
2
to N
2.
NAD(P)H shows an early small reduction which can be attributed to the interaction of a cytoplasmic pool with oxidases located in peroxisomes and the endoplasmic reticulum. Addition of amytal to the oxygenated perfusate produces a small additional oxidation of cytochrome b.