Fatty acid transport across lipid bilayer planar membranes

The transport of palmitic acid (PA) across planar lipid bilayer membranes w as measured using a high specific activity [C-14]palmitate as tracer for PA . An all-glass trans chamber was employed in order to minimize adsorbance o f PA onto the surface. Electrically neutral (diphytanoyl phosphatidylcholin e) and charged (Azolectin) planar bilayers were maintained at open electric circuit. We found a permeability to PA of (8.8 +/- 1.9) x 10(-6) cm s(-1) (n = 15) in neutral and of (10.3 +/- 2.2) x 10(-6) cm s(-1) (n = 5) in char ged bilayers. These values fall within the order of magnitude of those calc ulated from desorption constants of PA in different vesicular systems. Diff erences between data obtained from planar and vesicular systems are discuss ed in terms of the role of solvent, radius of curvature, and pH changes.