At physiologic albumin/oleate concentrations oleate uptake by isolated hepatocytes, cardiac myocytes, and adipocytes is a saturable function of the unbound oleate concentration. Uptake kinetics are consistent with the conventional theory. The Journal of c

To reexamine the role of albumin in cellular uptake of long chain fatty acids, we measured I3HIoleate uptake by isolated hepatocytes, adipocytes, and cardiac myocytes from incuba-tions containing oleate/albumin complexes at molar ratios from 0.01:1 to 2:1. For each ratio the uptake was studied over a wide range of albumin concentrations. In all three cell types and at any given oleate/albumin ratio, the uptake appeared saturable with increasing concentrations of oleate:albumin complexes despite the fact that the unbound oleate concentra-tion for each molar ratio is essentially constant. However, the "K." ' but not the "V,,,,C " of these pseudosaturation curves was influenced by substrate availability. At low albumin concentra-tions, uptake velocities did not correlate with unbound oleate concentrations. However, observed and expected uptake veloc-ities coincided at albumin concentrations approaching physio-logic levels and were a saturable function of the oleate/albumin ratios and the consequent unbound oleate concentrations em-ployed. Hence, under the experimental conditions employed in this study using a variety of suspended cell types, oleate uptake kinetics were consistent with the conventional theory at physi-ologic concentrations of albumin