Surface fluorescence of reduced pyridine nucleotide of the perfused rat kidney: interrelation between metabolic and functional states.

Surface fluorescence of reduced pyridine nucleotide (PN) was recorded continously with a DC fluorormeter and correlated with changes in experimental conditions. As a light source for fluorescence excitation, an Hg arc lamp with a 340-375 nm filter in front was used; the fluorescence response of reduced PN was measured at 450-510 nm. The DC fluormeter and the Hg arc lamp were connected to the kidney by a trifurcated fiber optics light guide. Reduced PN fluorescence emission was corrected for changes in tissue opacity by a 1:1 subtraction of reflectance changes at 340-375 nm from the fluorescence (PN-deltaR). To obtain further information about the PN redox state of the total surface area of kidney cortex and to evaluate whether certain areas were insufficiently perfused, fluorescence photographs of the total surface area were taken. The results demonstrate that the described method is simple and provides specific information about the mitochondrial oxidation reduction state.