Expression of aquaporin 1 (AQP1) water channels in human labial salivary glands

Aquaporin (AQP) water channels are widely expressed in the membranes of flu id-transporting epithelia. Despite the fact that salivary glands are the si te of considerable water movement, relatively little is known about the rol e of aquaporins in human salivary glands. We have examined the expression o f AQP1 in human parotid, sublingual and labial salivary glands. Total RNA w as extracted from glandular tissue obtained from surgery or biopsy. The pre sence of AQP1 mRNA was demonstrated in each of the three glands by RT-PCR u sing primers specifically designed for human AQP1. The PCR product from the labial gland RNA was further amplified with nested primers and the sequenc e confirmed by automated fluorescent DNA sequencing. The cleaned first PCR product from these glands was then used as a P-32-labelled hybridization pr obe in a Northern analysis which confirmed the presence of significant amou nts of AQP1 transcript in all three glands. AQP1 expression was also demons trated in cryosections of human labial glands by immunohistochemistry using peroxidase-linked antibodies. Antibody labelling was most prominent in the capillaries but was also evident in the basal regions of the labial gland acini, and may therefore be associated with the serous demilunes which are believed to be a significant site of fluid movement.