June 2020
Volume 61, Issue 7
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ARVO Annual Meeting Abstract  |   June 2020
Role of Aquaporin 4 in Lacrimal Gland Ductal Fluid Secretion in Mice
Author Affiliations & Notes
  • Dóra Szarka
    Department of Ophthalmology, University of Szeged, Szeged, Hungary
  • Greta Elekes
    Department of Ophthalmology, University of Szeged, Szeged, Hungary
  • Margaréta Korsós
    Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Csongrád, Hungary
  • Orsolya Berczeli
    Department of Ophthalmology, University of Szeged, Szeged, Hungary
  • Laszlo Szalay
    Department of Ophthalmology, University of Szeged, Szeged, Hungary
  • Denes Torok
    Department of Anatomy, University of Szeged, Szeged, Hungary
  • Edit Toth-Molnar
    Department of Ophthalmology, University of Szeged, Szeged, Hungary
  • Footnotes
    Commercial Relationships   Dóra Szarka, None; Greta Elekes, None; Margaréta Korsós, None; Orsolya Berczeli, None; Laszlo Szalay, None; Denes Torok, None; Edit Toth-Molnar, None
  • Footnotes
    Support  NKFIH NN 115611; EFOP-3.6.1-16-2016-00008; HARVO Travel Grant; SZTE ÁOK-KKA No 2018/Tóth-Molnár E
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 2620. doi:
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      Dóra Szarka, Greta Elekes, Margaréta Korsós, Orsolya Berczeli, Laszlo Szalay, Denes Torok, Edit Toth-Molnar; Role of Aquaporin 4 in Lacrimal Gland Ductal Fluid Secretion in Mice. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2620.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Aquaporins (AQPs) are transcellular water channels that can be essential in the physiology of various secretory epithelia. Although earlier reports demonstrated the predominant presence of AQP4 in the duct cells from rabbit lacrimal glands (LG) and substantial alterations of AQP4 mRNA levels were also demonstrated in experimental dry eye and during pregnancy, the functional relevance of AQP4 in LG duct secretion has to be clarified. In the present study, function of AQP4 in LG ductal fluid secretion was investigated using AQP4 knock out (KO) mouse strains.

Methods : Immunofluorescence was used to localize AQP4 protein in LGs. Duct segments were isolated from LGs of wild type (WT) and AQP4 KO mice as we previously described. Ends of the ducts seal during incubation forming a closed intraluminal space. Fluid secretion was quantified by video-microscopy. Ductal fluid secretions evoked by cell-permeable cAMP analogue (8-bromo cAMP, 100 μM); carbachol (100 μM); vasoactive intestinal peptide (VIP, 200 nM); and phenylephrine (PHE, 10 μM) were measured in WT and in AQP4 KO duct segments. Statistical significance was calculated with one-way ANOVA. Data were presented as means ± SEM. A p value of <0.05 was regarded as significant.

Results : Immunofluorescence demonstrated the predominant presence of AQP4 protein in the basolateral membranes of LG duct cells from WT mice. The secretory rates (Jv, pl/min/mm2) were calculated for the first 10 minutes of stimulation. Carbachol (WT: 215.7±73.9; AQP4 KO: 216.2±37.3; p=0,242), and PHE (WT: 248.5±91.3; AQP4 KO: 195.3±51.01; p=0,183) caused similar secretory responses in ducts from WT and AQP4 KO animals. In contrast, 8-bromo cAMP (WT: 190.5±22.4; AQP4 KO: 57.6±23.8; p=0.026), and VIP (WT: 256.3±51.02; AQP4 KO: 141.07±34.26; p=0.01) stimulation resulted in significantly reduced secretory rates in ducts from AQP4 KO LGs compared to WT LG ducts.

Conclusions : Our results demonstrate that AQP4 plays functional relevance in the fluid secretion of mouse LG ducts. Role of AQP4 seems to be different in fluid secretions stimulated by various secretagogues and its activity may be related to the intracellular mechanisms induced by the stimulatory agents i.e. cyclic AMP-mediated secretion proved to be reduced in AQP4 KO ducts. These assumptions need further investigations.

This is a 2020 ARVO Annual Meeting abstract.

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