EFFECT OF PAF ON POLYMORPHONUCLEAR LEUKOCYTE PLASMA-MEMBRANE POLARITY- A FLUORESCENCE STUDY

THE effect of PAF on the plasma membrane polarity of polymorphonuclear leukocytes (PMNs) was investigated by measuring the steady-state fluo rescence emission spectra of 2-dimethylamino(6-lauroyl) naphthalene (L aurdan), which is known to be incorporated at the hydrophobic-hydrophi lic interface of the bilayer, displaying spectral sensitivity to the p olarity of its surrounding. Laurdan shows a marked steady-state emissi on blue-shift in non-polar solvents, with respect to polar solvents. O ur results demonstrate that PAF (10(-7) M) induces a blue shift of the fluorescence emission spectra of Laurdan. These changes are blocked i n the presence of the PAF antagonist, L-659,989. Our data indicate tha t the interaction between PAF and PMNs is accompanied by a decrease in polarity in the hydrophobic-hydrophilic interface of the plasma membr ane.