High-resolution visualization of oxygen distribution in the liver in vivo

Abstract

Microcirculatory failure after stress events results in mismatch in oxygen supply and demand. Determination of tissue oxygen distribution in vivo may help elucidate mechanisms of injury, but present methods have limited resolution. Male Sprague-Dawley rats were anesthetized, prepared for intravital microscopy, and received intravenously the oxygen-sensitive fluorescent dye Tris(1,10-phenanthroline)ruthenium(II) chloride hydrate [[Formula: see text]]. An impaired hepatic oxygen distribution was induced by either phenylephrine or hemorrhage. Intensity of [Formula: see text] fluorescence was compared with NADH autofluorescence indicating changes in the mitochondrial redox potential. Ethanol was injected to affect the NADH-to-NAD+ ratio without altering the Po2. Infusion of [Formula: see text] resulted in a heterogeneous fluorescence under baseline conditions reflecting the physiological acinar Po2 distribution. A decrease in oxygen supply due to phenylephrine or hemorrhage was paralleled by an increase in [Formula: see text] and NADH fluorescence reflecting an impaired mitochondrial redox state. Ethanol did not alter [Formula: see text] fluorescence but increased NADH fluorescence indicating independence of Po2 and redox state imaging. Intravenous administration of [Formula: see text] for intravital videomicroscopy represents a new method to visualize the hepatic tissue Po2. Combined with NADH autofluorescence, it provides additional information regarding the tissue redox state.