Free fatty acid utilization by mammalian cell suspensions comparison between individual fatty acids and fatty acid mixtures

Abstract

Long-chain free fatty acid utilization by Ehrlich ascites tumor cell suspensions was compared when either one or a mixture of albumin-bound free fatty acids was present in the incubation medium. The percentage distribution of palmitate radioactivity in cell phospholipids, glycerides and cholesterol esters was similar when the medium contained either palmitate alone or an equimolar mixture of palmitate plus another fatty acid. Less palmitate was taken up and metabolized when a second fatty acid was available. However, at a given medium free fatty acid concentration and fatty acid-albumin molar ratio, total fatty acid utilization from an equimolar mixture of palmitate and oleate was intermediate between that occurring when palmitate and oleate were present alone. The major factor regulating fatty acid uptake and metabolism was the molar ratio of total free fatty acid to albumin when either one or a mixture of acids was available to the cells. During incubation with free fatty acid and glucose, the net increase in cell lipid ester content was not enhanced when palmitate was replaced by an equimolar mixture of palmitate and linoleate. Likewise, the incorporation of glucose radioactivity into cell lipids was only slightly greater when mixtures of free fatty acids were present instead of a single fatty acid. These findings suggest that the rates of fatty acid utilization observed in mammalian cell suspensions when only one acid is contained in the medium probably are adequate gross estimates of the capacity of that system to utilize free fatty acid.