Intrinsic uncoupling of mitochondrial proton pumps. 1. Nonohmic conductance cannot account for the nonlinear dependence of static head respiration on .DELTA.~.mu.H

Abstract

The passive membrane conductance LH1 of rat liver mitochondria has been measured and compared with the quantity nJesh/.DELTA.~.mu.Hsh (n = H+/e stoichiometry; Jesh = rate of electron transfer in static head) over a .DELTA.~.mu. range. The two curves approach each other only in the lower part of the range, while they sharply diverge at large values of .DELTA.~.mu.H. Thus nJesh/.DELTA.~.mu.Hsh cannot be considered to be a measure of LH1 in the upper .DELTA.~.mu.H region. Only a fraction of the static head electron flow is accounted for by futile proton cycling via leaks. Contaminating open membrane fragments or completely leaky mitochondria can be responsible for only a small part of the residual rate of oxygen consumption. We conclude that a large part of static head respiration must have yet another cause and propose it to be intrinsic uncoupling of the respiratory chain enzymes.