title: Spectral analysis of cytochromes in rat heart myocytes: transient and steady-state photodiode array spectrophotometry measurements.
abstract: Myocytes prepared from rat heart have been studied by optical spectroscopy using a photodiode array spectrophotometer adapted to a stopped flow apparatus (PASF). The isolated cells were viable for 3-4 h (i.e., over the total time of the experiments), as tested employing morphological parameters of cell damage, reactivity toward trypan blue, and the ability to use succinate in the absence and presence of digitonin. Respiration was activated by addition of sodium ascorbate and tetramethyl-para-phenylenediamine (TMPD) as exogenous reductants, in order to single out the contributions of cytochrome c and cytochrome c oxidase among the complexes of the mitochondrial respiratory chain. TMPD was shown to be freely permeable across cytoplasmic and mitochondrial membranes, with a measured KD = 0.9 mM. The use of singular value decomposition analysis coupled to PASF acquisition proved very powerful in resolving statically and kinetically, in the millisecond time region, the spectral contributions of the cytochromes. Spectral analysis was improved by adding carbon monoxide at concentrations which did not affect cytochrome c oxidase activity, but kept myoglobin fully saturated (and thus uninfluential to absorbance changes).
authors.affiliation: Department of Biochemical Sciences, University of Rome La Sapienza, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Sarti
authors.forename: G
authors.initials: G
authors.lastname: Antonini
authors.forename: F
authors.initials: F
authors.lastname: Malatesta
authors.forename: E
authors.initials: E
authors.lastname: D'Itri
authors.forename: M
authors.initials: M
authors.lastname: Brunori
authors.forename: T J
authors.initials: TJ
authors.lastname: Blanck
mesh_terms: D000818:Animals; D002470:Cell Survival; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism; D003580:Cytochromes / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism; D006321:Heart / Q000187:drug effects; D007700:Kinetics; D008929:Mitochondria, Heart / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013053:Spectrophotometry / Q000379:methods; D013772:Tetramethylphenylenediamine / Q000494:pharmacology
chemical_list: D003574:Cytochrome c Group; D003580:Cytochromes; D003576:Electron Transport Complex IV; D013772:Tetramethylphenylenediamine