Autofluorescence as a dynamic parameter of liver tissue energetic metabolism

Background/Objective: The autofluorescence properties of NAD(P)H and flavins - major electron carriers in energetic redox reactions—can be exploited for the assessment of the liver energetic metabolism engagement. The diagnostic significance of this tissue intrinsic parameter has been evaluated in terms of its dynamic response (time constant and amplitude) to different conditions affecting energetic metabolism. Study design: Autofluorescence response (Exc. 366 nm) of livers submitted either to acute damage, or to energetic metabolism alterations induced by hyperthyroidism (L-thyroxine 30 mg/100 g, b.w., i.p. injection, 7d.) was analyzed in situ upon ischemia/ reoxygenation conditions, via fiber-optic probe based spectrofluorometer. Results: The damage induced by treatments mimicking organ transplantation procedures affects the time constant of autofluorescence intensity decay upon reoxygenation, indicating an alteration of mitochondrial NAD(P)H re-oxidation reactions kinetics upon acute damage. The long term effects of hyperthyroidism on liver (increase in glycerol-phosphatedehydrogenase shuttle, lipogenesis), result in changes in both level and persistence of the signal amplitude upon ischemia reoxygenation conditions, in dependence on the relatively larger NADP(H) amount, related to the increased reductive biosynthesis (lipogenesis). Spectral fitting analysis provides information on the relative involvement of each fluorophore. Conclusions: The time course of tissue autofluorescence signal during ischemia/reoxygenation procedure provides information about the metabolic pathway involved in liver under different experimental conditions. Supported by MIUR ‘‘COFIN 2004’’.