Fatty Acids Enter Cells by Simple Diffusion

Abstract

Juxtaposed in this issue of the Proceedings are two short reviews on the cellular uptake of water-insoluble substances, in this case, long-chain fatty acids. These reviews reflect two different biases as to how fatty acids and similarly apolar substances enter cells: whether by simple diffusion regulated by the physical chemical properties of water, the lipid bilayer region of membranes, and fatty acids, or by a facilitated mechanism dependent on specialized binding proteins and carrier proteins. The mechanism of cellular uptake of molecules like long-chain fatty acids has broad biomedical importance. Elucidation of the mechanism has implications for pharmacokinetics, for predicting the pharmacokinetic behavior of new compounds, and potentially for directing compounds of a given structure to selected kinds of membranes. Yet the current views of the problem could not be more divergent.For example, a spontaneous mechanism for the uptake of the nonpolar compounds by cells predicts that solubility in plasma m...