Abstract
Purpose: :
The purpose of our study is to investigate potential roles of aquaporin–5 (AQP5) in saliva– and tear secretion.
Methods: :
AQP5–deficient (–/–) and wild–type (+/+) mice on the 129svJ Black Swiss background were used in all experiments. Collection of saliva and tear was performed after pilocarpine treatment (1mg/kg for saliva collection and 3mg/kg for tear collection). Saliva and tears were collected from the same mice for 15 min using calibrated microglass capillaries. Immunoblot and immunohistochemistry for AQP5 were performed in lacrimal glands and parotid glands.
Results: :
Pilocarpine–stimulated tear secretion in AQP5–deficient (–/–) mice (6.7±1.2 µL) was not significantly altered when compared to normalized values for wild types (5.8±0.7 µL). In contrast, saliva collected from pilocarpine–stimulated AQP5–deficient (–/–) mice (65±17 µL) was significantly decreased (approximately 80% lower) than saliva from wild–type mice (293±42 µL). Protein levels of AQP5 were lower in lacrimal glands than in parotid glands. Immunofluorescence demonstrated that AQP5 labelling was observed clearly in both duct cells as well as acinar cells of lacrimal glands. In contrast, in salivary glamds, AQP5 labelling was abundant in acinar cells but much less detectable in duct cells.
Conclusions: :
The expression level and cellular localization of AQP5 is considerably different between lacrimal glands and parotid glands. AQP5 is necessary for pilocarpine–treated saliva secretion but does not play as central a role in tear secretion in the mouse.
Keywords: lacrimal gland • ion channels • transgenics/knock-outs