To test the hypothesis that the expression of aquaporins (AQPs) 4 and 5 is altered in the lacrimal glands (LG) of rabbits with induced autoimmune dacryoadenitis (IAD).
LGs were obtained from adult female rabbits with IAD, and age-matched female control rabbits. LGs were processed for laser capture microdissection (LCM), real time RT-PCR, Western blot, and immunofluorescence for the detection and quantification of protein and mRNAs of AQP4 and AQP5 in whole LGs, and purified acinar cells and duct cells from specific duct segments.
In rabbits with IAD, abundances of mRNAs for AQP4 and AQP5 from whole LGs were significantly lower than controls. Levels of mRNA for AQP4 were lower in most duct segments from rabbits with IAD. However, the mRNA abundance for AQP5 was significantly lower in acini from rabbits with IAD, while its abundance was higher in each duct segment. Western blot showed that the expression of AQP4 in LGs from rabbits with IAD was 36% more abundant than normal controls, whereas AQP5 was 72% less abundant. Immunofluorescence indicated that AQP4 immunoreactivity (AQP4-IR) was present on the basolateral membranes of acinar and ductal cells in control and diseased LGs, with ductal cells showing stronger AQP4-IR than acinar cells. AQP5-IR was found on apical and basolateral membranes of acinar cells, and showed a "mosaic" pattern, i.e., with some acini and/or acinar cells showing stronger AQP5-IR than others. Minimal AQP5-IR was detected in ductal cells from control animals, while its intensity was significantly increased in rabbits with IAD.
These data strongly support our hypothesis that expressions of AQPs are altered in rabbits with IAD, and that specific ductal segment play important roles in lacrimal secretion.