The effect of respiration on the permeability of the mitochondrial membrane to ions.
1. The rates of cation uptake, for either organic cations such as tetrapropylammonium, TPA+, at variable tetraphenylboron concentrations, TPB-, or inorganic cations such as Mn2+, or K+ plus valinomycin, have been measured in mitochondria either respiring, under uncoupler titrations, or non-respiring, under variable K+ diffusion potentials. 2. The flow-force relationship for the respiration-coupled ion fluxes during titrations with uncouplers is almost identical to that obtained for the K(+)-diffusion driven fluxes. Similar results are obtained when TPA+ is replaced with inorganic cations, either monovalent such as K+ (+valinomycin), or divalent such as Mn2+. 3. By applying the Eyring analysis, as developed by Garlid et al. (Garlid, K.D., Beavis, A.D. and Ratkje, S.K. (1989) Biochim. Biophys. Acta 976, 109-121), from the flux-voltage relationships the values for the permeability coefficients and for the energy barriers have been obtained for the transport of the ion pair TPA(+)-TPB-, of Mn2+ and of K+ plus valinomycin, in non-respiring and in respiring, coupled and uncoupled, mitochondria. 4. The findings that the rates of respiration-coupled ion fluxes, at all values of membrane potential, are similar to the rates of the K+ diffusion potential-coupled ion fluxes and the similar pattern of the flux-voltage relationships during the titrations with uncouplers and artificial gradients indicate that the membrane permeability for ions is not modified by respiration.
Luvisetto
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C.N.R. Unit for the Study of Physiology of Mitochondria, University of Padova, Italy.
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Canton
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Azzone
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D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002412:Cations; D004058:Diffusion; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism*; D017136:Ion Transport; D007700:Kinetics; D008345:Manganese / Q000378:metabolism; D008564:Membrane Potentials; D008930:Mitochondria, Liver / Q000502:physiology* / Q000648:ultrastructure*; D010101:Oxygen Consumption; D010539:Permeability; D011188:Potassium / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D051381:Rats; D013775:Tetraphenylborate / Q000378:metabolism; D014634:Valinomycin / Q000494:pharmacology
D002412:Cations; D000644:Quaternary Ammonium Compounds; C052377:tetrapropylammonium; D014634:Valinomycin; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D008345:Manganese; D013775:Tetraphenylborate; D011188:Potassium