Interaction of arachidonic acid, oleic acid and anandamide with cholesterol monolayers.

<p><i>A</i>. Monolayers of pure cholesterol were prepared at the air-water interface at an initial pressure of 25 mN.m⁻¹. After stabilization of the monolayer, arachidonic acid (open squares), oleic acid (full triangles) or anandamide (full squares) were injected in the aqueous subphase at a final concentration of 50 nM. The data are expressed as the variation of the surface pressure as a function of time following the addition of the indicated lipid in the subphase. <i>B</i>. A monolayer of cholesterol (initial pressure of 25 mN.m⁻¹) was incubated with 750 nM of oleic acid added in the subphase. Under these conditions, the surface pressure of the monolayer rapidly increased and reached a stable value of 5 mN m⁻¹. After 400 seconds, 750 nM of anandamide (AEA, arrow) was injected in the aqueous subphase, which induced a dramatic surface pressure increase.