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P. Nandoskar, L. Parsa, Y. Wang, A. K. Mircheff, J. E. Schechter, P. B. Thomas, M. D. Trousdale, C. Ding; Ion Transporters in Rabbit Lacrimal Acinus-Duct Axis and Their Changes in Induced Autoimmune Dacryoadenitis. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4146.
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© ARVO (1962-2015); The Authors (2016-present)
Lacrimal gland (LG) fluid formation is mediated by ion transporters and aquaporins. Previous data indicated that levels of some transporter mRNAs are decreased in extracts of whole LG from rabbits with induced autoimmune dacryoadenitis (IAD). In this study we used confocal immunofluorescence microscopy, laser capture microdissection (LCM), and real time RT-PCR to investigate possible changes of ion transporter expression along the acinus-duct axis.
LG were obtained from female rabbits with IAD and age- and season-matched normal controls. LG were processed for both LCM and stained with antibodies for Na-K-2Cl co-transporter-1 (NKCC1), Na-K-ATPase β1 subunit (NKAβ1), Na-H exchanger 1 (NHE1) and the cystic fibrosis transmembrane conductance regulator (CFTR).
NHE1 immunoreactivity (IR) was found at the basolateral membrane (BLM) and within the cytoplasm of all acinar and ductal cells, but the level in ductal cells was considerably higher. NKCC1 IR also was present at BLM and within the cytoplasm of all acinar and ductal cells, but the levels were markedly higher in acinar cells. NKAβ1 IR was present in all acinar cells, but levels differed in a "mosaic" pattern, higher in some acinar cells and/or acini than others; NKAβ1 IR in ductal cells was uniformly high. CFTR IR was present in punctate aggregates within the apical cytoplasm of all acinar and ductal cells, but the level in ductal cells was higher. NHE1 IR intensity was higher in IAD acini than control acini. In contrast, the distributions and intensities of NKCC1-, NKAβ1-, and CFTR IRs did not differ significantly between control and IAD. Distributions of transporter mRNA abundances accorded with the general distributions of the IRs along the acinus-duct axis, but relative levels were considerably lower in IAD acini.
The preferential localizations of NHE1 and CFTR in ductal cells and of NKCC1 in acinar cells, strongly support the concept that acini and ducts play different roles in LG secretion. The marked differences in mRNA abundances between control and IAD contrast with the similar IR levels of NKCC1, NKAβ1, and CFTR. This is consistent with the notions that: (a) The transporters cycle between large cytoplasmic pools and small plasma membrane pools; (b) IAD is associated with decreased rates of both synthesis and degradation suggested by decrease level of mRNA; (c) Chronic stimulation in inflammatory states such as IAD decreases traffic of transporters to the cells’ degradative compartments, leaving steady-state transporter protein levels unchanged.
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