Abstract
Abstract: :
Purpose:Tear lipocalin (TL) (∼18 kDa), a member of the lipocalin family, has been identified as one of the major proteins of lacrimal fluid in rabbits. Rabbits are a good model for studying factors affecting lacrimal gland function, and measurement of TL can be used as a marker for lacrimal gland performance. Dry eye occurs mostly after menopause when the production of estrogens and androgens are significantly decreased, and the concentration of TL has been found to be decreased in the tears of patients suffering of this disease. Based on this fact, we postulate that these sex hormones might influence TL expression. Methods:Pilocarpine–stimulated lacrimal fluid was collected by cannulation of the lacrimal duct using polyethylene PE 10 tubing, from sexually mature (3.5–4.0 kg) New Zealand white rabbits after 7 days of being: a) sham–operated, b) ovariectomized (OVX), c) OVX and treated simultaneously with dihydrotestosterone (DHT) (4 mg/kg/day), and d) OVX and treated simultaneously with 17 ß–estradiol (0.5 mg/kg/day) (n=4). Lacrimal fluid (15 µg protein) was then analyzed by SDS PAGE gel electrophoresis and Western blot using a polyclonal rat anti–rabbit TL antibody. Semi quantitation analysis of the bands was performed by densitometry. Results:The results of the densitometric analysis showed that ovariectomy decreased TL expression by 35%, while DHT and 17 ß–estradiol treatment significantly increased the expression of TL in the lacrimal fluid over control values by 300 % and 200 %, respectively. Conclusions:These experiments support the hypothesis that sex hormones influence the expression of TL in rabbit lacrimal glands. A decrease in TL could contribute to the development of dry eye.
Keywords: lacrimal gland • cornea: tears/tear film/dry eye • protein structure/function