title: Assessment of mitochondrial membrane potential in proximal tubules after hypoxia-reoxygenation.
abstract: Proximal tubules develop a severe energetic deficit during hypoxia-reoxygenation (H/R) that previous studies using fluorescent potentiometric probes have suggested is characterized by sustained, partial mitochondrial deenergization. To validate the primary occurrence of mitochondrial deenergization in the process, optimize approaches for estimating changes in mitochondrial membrane potential (DeltaPsim) in the system, and clarify the mechanisms for the defect, we further investigated the behavior of 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazocarbocyanine iodide (JC-1) in these cells and introduce a more dynamic and quantitative approach employing safranin O for use with the tubule system. Although use of JC-1 can be complicated by decreases in the plasma membrane potential that limit cellular uptake of JC-1 and such behavior was demonstrated in ouabain-treated tubules, changes in DeltaPsim entirely accounted for the decreases in the formation of red fluorescent JC-1 aggregates and in the ratio of red/green fluorescence observed after H/R. The red JC-1 aggregates did not readily dissociate when tubules were deenergized after JC-1 uptake, making it unsuitable for dynamic studies of energization. Safranin O uptake by digitonin-permeabilized tubules required very small numbers of tubules, permitted measurements of DeltaPsim for relatively prolonged periods after the end of the experimental maneuvers, was rapidly reversible during deenergization, and allowed for direct assessment of both substrate-dependent, electron transport-mediated DeltaPsim, and ATP hydrolysis-supported DeltaPsim. Both types of energization measured using safranin O in tubules permeabilized after H/R were impaired, but combining substrates and ATP substantially restored DeltaPsim.
authors.affiliation: Nephrology Div., Dept. of Internal Medicine, Rm. 1560, MSRB II, Univ. of Michigan Medical Ctr., Ann Arbor, MI 48109-0676, USA.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Feldkamp
authors.forename: Andreas
authors.initials: A
authors.lastname: Kribben
authors.forename: Joel M
authors.initials: JM
authors.lastname: Weinberg
mesh_terms: D058186:Acute Kidney Injury / Q000503:physiopathology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001562:Benzimidazoles / Q000493:pharmacokinetics; D002232:Carbocyanines / Q000493:pharmacokinetics; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D004396:Coloring Agents / Q000493:pharmacokinetics; D004734:Energy Metabolism / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D000860:Hypoxia / Q000503:physiopathology*; D007476:Ionophores / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology; D010619:Phenazines / Q000493:pharmacokinetics; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011817:Rabbits
chemical_list: D001562:Benzimidazoles; D002232:Carbocyanines; D004396:Coloring Agents; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007476:Ionophores; D010619:Phenazines; C068624:5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D010042:Ouabain; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; C009195:safranine T