Permeability of nitric oxide through lipid bilayer membranes

Profiles of the local nitric oxide (. NO) diffusionconcentration product across the egg yolk phosphatidylcholine membrane in the absence and presence of 30 mol% cholesterol were obtained using line-broadening electron paramagnetic resonance (EPR) and lipid-soluble nitroxide spin labels. Membrane . NO permeability coefficients were calculated from these profiles. At 20 degrees C, values of 93 and 77 cm/s for membranes in the absence and presence of cholesterol were obtained, compared with 73 and 66 cm/s for water layers of the same thickness as the membranes. Fluid-phase membranes are hot barriers to . NO transport. Cholesterol significantly increases . NO transport in the center of the lipid bilayer.