Effect of free fatty acid structure on binding to rat liver mitochondria

Abstract

We have compared the binding of seven long-chain free fatty acids to rat liver mitochondrial suspensions. Bovine serum albumin was present in the incubation medium, and the fatty acid-albiumin molar ratio was varied between 0.5 and 5.5. A steady-state amount of radioactive fatty acid was recovered from the mitochondria after 2 min of incubation at 23°. Most of the fatty acid uptake was due to transfer from albumin to the mitochondria, not incorporation of the intact fatty acid-albumin complex. Uptake of the saturated fatty acids increased as the chain length increased: lauric < myristic < palmitic < stearic. Saturated fatty acids of a given chain length were taken up to a greater extent than the corresponding unsaturated fatty acids: palmitate > palmitoleate; stearate > oleate or linoleate. Almost all of the newly incorporated fatty acid was bound reversibly in unesterified form and was associated with the mitochondrial membranes. These findings suggest that the differences in uptake of the various free fatty acids result at least partly from differences in binding to the mitochondrial membranes.