Inhibitory effect of Mg2+ on the protonophoric activity of palmitic acid.
To discriminate whether fatty acids are uncouplers that cause acceleration of State-4 respiration, associated with a decrease in the protonmotive force, or decouplers that increase respiration without associated decrease in the protonmotive force, we examined the effect of palmitate on functions of rat-liver mitochondria under various conditions. We found that palmitate itself increases State-4 respiration, releases oligomycin-inhibited State-3 respiration, inhibits ATP synthesis and ATP<->Pi exchange reaction, and increases H+ permeability in mitochondrial and model bilayer phospholipid membranes. Thus, palmitate is a classical uncoupler of oxidative phosphorylation. However, these effects were inhibited by Mg2+, due to rapid formation of a stable complex between palmitate and Mg2+.
Shinohara
Y
Y
Faculty of Pharamceutical Sciences, University of Tokushima, Japan.
Unami
A
A
Teshima
M
M
Nishida
H
H
van Dam
K
K
Terada
H
H
D000818:Animals; D006863:Hydrogen-Ion Concentration; D007476:Ionophores; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000494:pharmacology*; D006180:Proton-Translocating ATPases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014475:Uncoupling Agents; D014634:Valinomycin / Q000494:pharmacology
D007476:Ionophores; D010169:Palmitic Acids; D014475:Uncoupling Agents; D014634:Valinomycin; D019308:Palmitic Acid; D006180:Proton-Translocating ATPases; D008274:Magnesium