Intravital multiphoton imaging of rhodamine 123 in the rat liver after intravenous dosing

Abstract

Intravital imaging with multiphoton microscopy was used to investigate the hepatic disposition of rhodamine 123 (RH123) in the exposed liver of anesthetized rats after intravenous dosing. The role played by the biliary canalicular transporter P-glycoprotein (P-gp) on the disposition of RH123 was explored by administering a P-gp inhibitor, cyclosporine A prior to RH123 administration. The fluorescence intensity of RH123 was defined by multiphoton microscopy using a femtosecond laser excitation wavelength of 900 nm whereas the autofluorescence at an excitation wavelength of 740 nm was used to define the morphology of the liver acini. Intravital imaging showed that RH123 was rapidly taken up from the sinusoids into hepatocytes but slowly eliminated from the cells (half-life 2.89 ± 1.37 h). The presence of cyclosporine A did not affect the uptake of RH123 but markedly increased the fluorescence intensity of RH123 in the liver and was associated with a slower elimination of RH123 from the liver (half-life 11.5 ± 4.24 h). In conclusion, the spatial disposition of RH123 in the rat liver and the effects of a transporter inhibitor on its disposition have been monitored over time using intravital imaging.