title: Contribution of the mitochondrial compartment to the optical properties of the rat liver: a theoretical and practical approach.
abstract: The purpose of this work was to analyze the contribution of the mitochondria to the optical properties, i.e., light absorption and scattering, of the blood-free rat liver. Firstly, a theoretical model of the reduced scattering coefficient of the liver was performed by using the Mie theory, the Rayleigh-Debye-Gans approximation, and the electron microscopy descriptions of the liver ultrastructure. Compared with the hepatocyte volume, the nucleus and the peroxisomes, the mitochondria compartment, accounting for 22% of the liver cell volume, seemed to be the predominant factor for the light scattering of the liver. Second, by using time-resolved spectroscopy and a sample substitution method, we have measured the absorption and reduced scattering coefficients of blood-free perfused rat livers, isolated hepatocyte suspensions, and isolated mitochondria suspensions. A subsequent extrapolation of the isolated mitochondria data to the in vivo mitochondrial content and a comparison with the whole liver measurements lead to the following conclusions: 1) the mitochondria account for about 50% of the liver absorption coefficient at 780 nm (mu a = 0.25 cm-1 extrapolated from isolated mitochondria vs. 0.53 +/- 0.05 cm-1 measured for the liver); and 2) the mitochondrial compartment is the primary factor for the light scattering in the rat liver (mu s' = 15.5 cm-1 extrapolated from the isolated mitochondria versus 15.9 +/- 2.4 cm-1 measured for the liver), demonstrating the relevancy of our preliminary theoretical study.
authors.affiliation: Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104.
authors.forename: B
authors.initials: B
authors.lastname: Beauvoit
authors.forename: T
authors.initials: T
authors.lastname: Kitai
authors.forename: B
authors.initials: B
authors.lastname: Chance
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D066298:In Vitro Techniques; D008027:Light; D008099:Liver / Q000737:chemistry / Q000166:cytology; D008297:Male; D008930:Mitochondria, Liver / Q000737:chemistry*; D008954:Models, Biological; D055095:Optics and Photonics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012542:Scattering, Radiation; D013055:Spectrophotometry, Infrared; D013347:Subcellular Fractions / Q000737:chemistry