Oleate oxidation and mitochondrial substrate selection in vascular smooth muscle

The purpose of th is study was to determine the contribution of long-chain fatty acids relative to other mitochondrial substrates in active vascular s mooth muscle (VSM). Hog carotid arteries were isometrically contracted in p hysiological saline solution containing 0.71 mM U-(13)Coleic acid (bound to albumin at a ratio of 6.8:1), 5 mM 1-C-13-glucose and 1 mM acetate in the presence or absence of 5 mM carnitine for 6 h at 37 degreesC. Substrate oxi dation was determined using C-13-isotopomer analysis of glutamate. Although oxidation of oleic acid could not be measured at physiological concentrati ons [0.5 mM(1:1)], oleic acid oxidation was approximately 5% of the total s ubstrates oxidized at the higher concentration examined. Although insignifi cant, carnitine increased oleic acid oxidation to approximately 8%, and res ulted in a decrease in endogenous lipid oxidation, which was 2-12% of the t otal substrates oxidized. Oxidation of glucose and acetate did not signific antly change due to the inclusion of oleic acid in the incubation solutions . Therefore, we conclude that exogenous long-chain fatty acids are minor co ntributors to substrate oxidation (approximately 5%) in VSM compared to oth er mitochondrial substrates, such as glucose and acetate, which account for approximately 80% of the substrates oxidized by VSM. Copyright (C) 2001 S. Karger AG, Basel.