Aims: 

Changes in the extracellular milieu can affect organ development and protein expression. We have previously studied aquaporin expression profiles in mouse embryonic salivary glands, in addition to the effect of varying extracellular osmolalities on aquaporin expression in a salivary gland cell line. Here we examine whether osmolality variations affect salivary development and aquaporin expression.

Methods: 

Submandibular salivary glands (SMGs) were dissected from E13.5 mice and cultured in standard conditions in DMEM/F12 on filters in microwell dishes. Glands were cultured for 24h in isosmotic (310 mOsm), hyperosmotic (350 mOsm), or hypoosmotic (270 mOsm) culture media (total 135 glands) and photographed at 1 and 24 h. Real time-PCR was used to analyse AQP3, 4, and 5 expression. MetaMorph software was used to measure gland areas and bud development.

Results: 

Glandular growth was similar in both isosmotic and hyperosmotic conditions (110 and 100% relative area increase, respectively). But glandular growth in hypoosmotic conditions was significantly decreased (10% relative area increase, P<0.001). Glandular budding was significantly decreased in the hypoosmotic and hyperosmotic media (20% decrease, P<0.001 and 110% increase, P=0.01, respectively) compared to isosmotic conditions (250% relative budding increase). Furthermore, AQP5 expression showed a 20% upregulation in glands cultured in hyperosmotic medium (P<0.005). The rest of the aquaporins showed a 4–14% expression decline (P<0.05).

Conclusion: 

Salivary gland morphogenesis and growth can be influenced by variations in extracellular osmolality. AQP5 expression seems to be most sensitive to the osmolality changes. Our findings indicate that this aquaporin may hold a special role in adaptations to varying osmolalities.