CFTR-Mediated Cl⁻ Transport in the Acinar and Duct Cells of Rabbit Lacrimal Gland

Abstract

Purpose: We investigated the role that the cystic fibrosis transmembrane conductance regulator (CFTR) may play in Cl⁻ transport in the acinar and ductal epithelial cells of rabbit lacrimal gland (LG).

Methods: Primary cultured LG acinar cells were processed for whole-cell patch-clamp electrophysiological recording of Cl⁻ currents by using perfusion media with high and low [Cl⁻], 10 µM forskolin and 100 µM 3-isobutyl-1-methylxanthine (IBMX), the non-specific Cl⁻ channel blocker 4,4′-disothiocyanostilbene-2, 2′ sulphonic acid (DIDS; 100 µM) and CFTRinh-172 (10 µM), a specific blocker for CFTR. Ex vivo live cell imaging of [Cl⁻] changes in duct cells was performed on freshly dissected LG duct with a multiphoton confocal laser scanning microscope using a Cl⁻ sensitive fluorescence dye, N-[ethoxycarbonylmethyl]-6-methoxy-quinolinium bromide.

Results: Whole-cell patch-clamp studies demonstrated the presence of Cl⁻ current in isolated acinar cells and revealed that this Cl⁻ current was mediated by CFTR channel. Live cell imaging also showed the presence of CFTR-mediated Cl⁻ transport across the plasma membrane of duct cells.

Conclusions: Our previous data showed the presence of CFTR in all acinar and duct cells within the rabbit LG, with expression most prominent in the apical membranes of duct cells. The present study demonstrates that CFTR is actively involved in Cl⁻ transport in both acinar cells and epithelial cells from duct segments, suggesting that CFTR may play a significant role in LG secretion.

KEYWORDS::

• CFTR
• Chloride channel
• Lacrimal gland
• Dry eye

ACKNOWLEDGEMENTS

The authors greatly thank Dr. Shenfeng Qiu for his expert advice in electrophysiological recordings of acinar cells and data analysis; Dr. Sarah Hamm-Alvarez for help in acinar cell culture; Dr. Janos Peti-Peterdi for help in duct cells imaging; Drs. Austin Mircheff and Joel Schechter for helpful discussions; Hua Pei and Francie Yarber for excellent technical support.

Declaration of interest:This work was supported by NIH grants EY017731, EY016985, EY10550, EY005801, RR024754. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this paper.