Ischemia-reperfusion injury, a common complication during liver surgery where steatotic livers are more prone to the injury, may become more prevalent in the growing obese population. This study characterizes liver morphology toward understanding changes in subcellular function in steatotic livers exposed to
ischemia-reperfusion injury through quantitative description of
fluorescein distribution obtained by minimally invasive in vivo multiphoton microscopy using a physiologic pharmacokinetic model. Rats were fed a high-fat diet for 7 days to induce
liver steatosis. Partial
ischemia was induced after reperfusion for 4 hours, when
fluorescein (10 mg/kg) was injected intravenously. Liver images, bile, and blood were collected up to 180 minutes after injection.
Ischemia-reperfusion injury was associated with an increase in
alanine transaminase levels and apoptosis. In addition, steatosis featured lipid droplets and an increase in
fluorescein-associated fluorescence observed in hepatocytes via multiphoton imaging. Analysis of the hepatic concentration-time profiles has suggested that the steatosis-induced increase in
fluorescein-associated fluorescence mainly arises by inducing hepatic
fluorescein metabolism. The combination of
ischemia-reperfusion with steatosis exacerbates these effects further. This was confirmed by fluorescence lifetime imaging microscopy showing a decreased average fluorescence lifetime of the liver, which is indicative of an increased production of the metabolite. Our results show the potential of noninvasive
dye imaging for improving our understanding of
liver disease induced by subcellular changes in vivo, providing further quantitative measures of metabolic and biliary liver function, and hence extending the qualitative liver function tests now available.