Pharmacokinetic analysis of platelet-activating factor in the tears of guinea pigs with allergic conjunctivitis.

The aim of this study was to examine the levels of platelet-activating factor (PAF) and lyso-PAF in tears from experimental animals developing allergic conjunctivitis (AC). AC was induced in guinea pigs by application of ovalbumin in eye drops. Tear samples were collected from 5 actively sensitized animals and from 5 unsensitized control animals before the challenge, and 1, 2, 4, and 6 h postchallenge. C18:0-PAF, C18:0-lyso-PAF, C16:0-PAF, and C16:0-lyso-PAF levels in the tear samples were determined using liquid chromatography-tandem mass spectrometry. The concentrations of C16:0-PAF, C16:0-lyso-PAF, and C18:0-lyso-PAF were measurable in both unsensitized and sensitized groups, whereas C18:0-PAF was undetectable in tear samples from either group. The levels of C16:0-PAF, C16:0-lyso-PAF, and C18:0-lyso-PAF in sensitized animals increased throughout the time course of the experiment, whereas there was no corresponding increase in the levels of these molecules in the unsensitized group. There were strong correlations between the concentrations of C16:0-PAF and C16:0-lyso-PAF, both in the sensitized and in the unsensitized group, and the concentrations of C16:0-lyso-PAF and C18:0-lyso-PAF within each group. The data from this study demonstrated that the levels of PAF and lyso-PAF increase in tears in a guinea pig model of AC development and implicate a role for PAF for the development of AC.