Platelet-Activating Factor in Human Normal Tears

To measure the concentrations of platelet-activating factor (PAF) and lyso-PAF in tears of human eyes.Unilateral tear samples were collected from the conjunctival cul-de-sac of 12 healthy volunteers without any past histories of ocular surface diseases and 10 patients with allergic conjunctivitis (AC) by graduated disposable microcapillaries. C18:0-PAF, C18:0-lyso-PAF, C16:0-PAF, and C16:0-lyso-PAF levels were determined by liquid chromatography-tandem mass spectrometry (LC/MS/MS).The concentrations of C18:0-PAF, C18:0-lyso-PAF, C16:0-PAF, and C16:0-lyso-PAF in tears from healthy volunteers were 0.44 +/- 0.39, 51.7 +/- 63.4, 61.9 +/- 75.9, and 10.7 +/- 14.7 ng/ml, respectively. Higher, but not significantly different, concentrations of all the four kinds of PAF molecules were detected in tears from AC patients. Significant correlations were demonstrated between the concentrations of C18:0-PAF and C18:0-lyso-PAF (r = 0.906; p < 0.01 in normal healthy volunteers and r = 0.939; p < 0.01 in AC patients), and between those of C16:0-PAF and C16:0-lyso-PAF (r = 0.944; p < 0.01 in normal healthy volunteers and r = 0.806; p = 0.015 in AC patients). Moreover, C18:0-PAF concentrations correlated significantly with those of C16:0-PAF (r = 0.885; p < 0.01 in normal healthy volunteers and r = 0.927; p < 0.01 in AC patients), while C18:0-lyso-PAF concentrations correlated significantly with those of C16:0-lyso-PAF (r = 0.972; p < 0.01 in normal healthy volunteers and r = 0.891; p < 0.01 in AC patients).To our knowledge, this is the first report of the concentrations of different species of PAF (C18:0-PAF, C18:0-lyso-PAF, C16:0-PAF, and C16:0-lyso-PAF) in human tears.