MORPHOLOGY OF LACRIMAL GLANDS AND HARDERIAN GLAND IN LABORATORY RATS

Lacrimal apparatus of laboratory rodents and, in particular, rats has been comparatively well studied. The history of its research was presented in works by Levental and Kulchitskyi (1894, 1911.). The structure of human’s lacrimal glands has being studied and completed. Much attention was paid to the drainage of tears from the lacrimal sac to nasolacrimal canal in the humans and rats, age-related changes of secretory epithelium in lacrimal glands of rats, detailed study of the major lacrimal glands in humans (palpebral and orbital lobes). Otherwise, tear-producing and tear-secreting parts of human lacrimal apparatus are understudied organ microcomplexes. This research paper descrides the morphological and functional peculiarities of tear secretion ducts under normal functioning of lacrimal glands.Rats have two paired lacrimal glands. One of glands, smaller in size, is intraorbital (infraorbital) and another, larger, is exoorbital one. Exoorbital gland is larger than intraorbital one. Ducts of these glands join before opening through common duct into conjunctival sac in the external corner of the eye. Both lacrimal glands of rats originate from common embryonic germ and perform the same function and thus, are of the similar histological structure. Moreover, they demonstrate similar spectrum of age-related changes in the morphology. Orbits of rats whithin their boundaries form one more glandular formation, Harderian glands. They release the secretion, rich in lipids and porphyrines. Some scientists report that there no glands like those in humans, but others support the idea that they are in their germinal state. Changes in rats’ lacrimal glands and in Harderian glands can serve as models for simulating diseases of human lacrimal apparatus. This modeling requires in-depth study of spatial organization of the system of excretory ducts and their terminal excretory ducts in syntopic unity with hemomicrocirculatory bed of lacrimal glands in lab rats and humans. It is also important to carry out comparative morphological and stereomorphological analysis of data received, and to describe the peculiarities of the structure of lacrimal glands in lab rats and person.

Evaluating the Functionality of Conjunctiva Using a Rabbit Dry Eye Model

Purpose.To assess the conjunctival functionality in a rabbit dry eye (DE) model.Methods.Nictitating membrane, lacrimal and Harderian glands were surgically excised from male New Zealand white rabbits using minimally invasive surgery. Fluorescein/rose Bengal staining of ocular surface (OS) and Schirmer test were done before (BE) and after excision (AE). The expression of interleukin- (IL-) 1β, tumor necrosis factor- (TNF-)α, and MUC5AC proteins were estimated by immunoblotting from conjunctival impression cytology specimens. MUC5AC mRNA was quantified as well. The effect of epithelial sodium channel (ENaC) blockers on tear production and potential differences (PD) of OS were assessed under anesthesia in rabbits with and without surgery.Results.Increase in corneal and conjunctival staining was observed 1 month AE compared to BE. Schirmer tests failed to show decrease in tear production. Elevated IL-1β, and TNF-α, 1 month AE indicated inflammation. MUC5AC expression was elevated 1 month AE. ENaC blockers did not improve tear production in rabbit eyes AE but characteristic changes in PD were observed in rabbits with surgery.Conclusions.DE biomarkers are important tools for OS assessment and MUC5AC expression is elevated in rabbit DE. PD measurement revealed significant electrophysiological changes in rabbits with surgery.