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M Yamada, R Arita, M Kawai, Y Mashima; Increased Secretory Phospholipase A2 Activity in Tears from Patients with Meibomian Gland Dysfunction . Invest. Ophthalmol. Vis. Sci. 2002;43(13):48.
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Purpose: Secretory phospholipase A2 (sPLA2) is the enzyme that hydrolyzes phospholipids, one of the important components of the lipid layer of tears. This study was performed to determine sPLA2 activity in tears from patients with meibomian gland dysfunction. Methods: Eight patients with obstructive meibomitis, 14 patients with seborrheic meibomitis, and 8 patients with Staphylococcal blepharitis participated in this study. Fourteen age-matched normal subjects served as controls. Five microliters of unstimulated tear was collected with a micropipette from the inferior tear meniscus in one eye of all subjects. sPLA2 activity in tears was measured by the use of 1, 2-diheptanoyl thio-phosphatidylcholine as a substrate. Free thiols from the hydrolysis by sPLA2 were detected using DTNB at 405 nm. Results: The activity of sPLA2 in tears from normal controls was 0.18 ± 0.07 µmol/min/µL (mean ± standard deviation). The sPLA2 activities in tears from patients with obstructive meibomitis, seborrheic meibomitis, and Staphylococcal blepharitis were 0.39 ± 0.11, 0.26 ± 0.12, and 0.47± 0.07, respectively. The mean sPLA2 activity of meibomian gland dysfunction was higher than that of normal controls with a statistical significance. Conclusions: sPLA2 activity was enhanced in tears from meibomian gland dysfunction when compared with that of normal controls. The increased enzymatic activity may play a role in the tear film instability seen in meibomian gland dysfunction through the hydrolysis of phospholipids and the production of free fatty acids in tears.
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