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.
C.N.R. Unit for the Study of Physiology of Mitochondria, University of Padova, Italy.
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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