The utilization by rabbit aorta of carbohydrates, fatty acids, ketone bodies, and amino acids as substrates for energy production.

Abstract

The ability of rabbit aorta to oxidize various substrates was studied to determine which of these compounds may be energy substrates for vascular smooth muscle (VSM). Glucose, ketone bodies, medium-chain length fatty acids, branched-chain amino acids, and glutamine all are oxidized at comparable rates on a molar basis. Some other amino acids, long chain fatty acids, pyruvate and glycerol also are oxidized, but at lower rates. The oxidation of 6 amino acids could not be detected. VSM was found to release ketone bodies when incubated in leucine beta-hydroxybutyrate or octanoate. This suggests that the acetoacetyl CoA and/or acetoacetate derived from these substrates is not completely oxidized. The oxidation rate of several substrates when measured individually is inhibited by 50-80% by the presence of a combination of other substrates in the medium. Under these conditions, glucose is a minor substrate for oxidative metabolism accounting for only 5% of O2 consumption. The oxidation rate of all the exogenous substrates together is calculated to account for less than half of the oxygen consumption; this finding indicates that an endogenous substrate must also be utilized.