AJP - Heart and Circulatory Physiology, Vol 243, Issue 1 128-H132, Copyright © 1982 by American Physiological Society
Utilization of endogenous lipid, glycogen, and protein by rabbit aorta
R. Odessey and K. V. Chace
The utilization of endogenous stores by rabbit aorta in vitro was measured.
In substrate-free medium glycogen disappearance may account for less than
20% of the tissue O2 consumption during incubations of less than 2-3 h. At
longer times (or in the presence of glucose) glycogen catabolism is
negligible. Calculations from the rate of proteolysis suggest that
oxidation of endogenously generated amino acids accounts for less than
7-10% of the oxygen consumption. Furthermore, the presence of
amino-oxyacetate, a transaminase inhibitor, did not alter the ATP-ADP
ratio. By contrast, measurements of the disappearance of tissue
triglyceride indicate that endogenous lipid could meet the fuel
requirements of the aorta. Direct measurement of intracellular fatty acid
oxidation was obtained by measuring acyl carnitine specific activity and
14CO2 production from [1-14C]palmitate. Fatty acid oxidation could account
for at least 90% of the total O2 consumption, and 83% of the fatty acids
consumed were derived from endogenous tissue stores. Octanoate was found to
inhibit both exogenous and endogenous fatty acid oxidation. These findings
may indicate that shorter-chain fatty acids may be preferentially utilized
by the aorta.
