Histochemical and Immunohistochemical Identification of Mast Cells in the Rat Lacrimal Glands

This study aims to investigate the presence, microanatomical localization, and immunohistochemical subtypes of mast cells in the lacrimal glands (LGs) of rats.

A total of ten female Sprague-Dawley rats' LGs were evaluated in this study.

The experimental animals were euthanized. LG samples were collected and fixed in 10% neutral formaldehyde for 48 h. Sections were taken from the paraffin-embedded samples and stained for microscopic examination. The histochemical properties of lacrimal gland epithelium and the composition of tears were examined by Periodic acid-Schiff and Alcian blue staining and evaluated microscopically. Toluidine blue staining and tryptase and chymase immunohistochemically demonstrated localization and phenotypes of mast cells.

The existence and varying numbers of mast cells were successfully demonstrated in all three LGs by Toluidine blue staining, and the highest number of mast cells was observed in the extraorbital lacrimal gland, while their numbers were almost the same in the intraorbital lacrimal gland and Harderian gland. Immunohistochemically, chymase-positive mast cells were more numerous than tryptase-positive cells.

This study is the first documentation of the presence of mast cells with different phenotypes in rat LGs.