AJP - Heart and Circulatory Physiology, Vol 249, Issue 4 723-H728, Copyright © 1985 by American Physiological Society
Effect of fatty acid oxidation on efficiency of energy production in rat heart
J. F. Hutter, H. M. Piper and P. G. Spieckerman
Myocardial fatty acid oxidation has been reported to be accompanied by an
elevated O2 consumption compared with carbohydrate oxidation. The exact
amount of this additional O2 consumption is controversial. Different
investigators have observed an O2 wasting effect that is too large to be
explained by the different ATP-to-O2 ratios of these substrates. With the
use of isolated perfused rat hearts, O2 consumption and hemodynamic
measurements were computer analyzed to provide on-line estimates of the
ratio between O2 consumption and demand (EQ). Increasing palmitate or
octanoate concentrations decreased the respiratory quotient, which was
accompanied by a disproportionate increase of EQ. Inhibition of fatty acid
oxidation by an inhibitor of acylcarnitine transferase or a blockade of
mitochondrial thiolase caused a drastic reduction of fatty acid oxidation.
The fatty acid-induced enhancement of O2 consumption was decreased to a
much smaller extent, indicating that there are two different mechanisms
responsible for the O2-wasting effect, one that depends on mitochondrial
fatty acid oxidation and another that is not affected by an inhibition of
this pathway.
