Original Paper

Mineralocorticoid Hormone Signaling Regulates the ‘Epithelial Sodium Channel’ in Fibroblasts from Human Cornea
Massoud Mirshahi^a, Shahsultan Mirshahi^a, Nady Golestaneh^a, Corinne Nicolas^a, Zohar Mishal^b, Karim C. Lounes^a, Christianne Hecquet^a, Françoise Dagonet^a, Yves Pouliquen^a, Manjul K. Agarwal<sup>c

a</sup>Inserm XR-86 et CNRS, Centre des Cordeliers, et Inserm U-9912, Paris;
^bLaboratoire de cytométrie, CNRS IFC 122,
^cDépartement de biologie et pharmacologie structurales, UMR 8532 CNRS, Villejuif, France

Address of Corresponding Author

Ophthalmic Res 2001;33:7-19 (DOI: 10.1159/000055635)

  Key Words

• Cornea
• Fibroblasts
• Aldosterone
• Mineralocorticoid receptor
• Sodium channel

  Abstract

We investigated the regulation of sodium absorption by steroid hormones in embryologically diverse cells from the human eye. A cell extract from human corneal fibroblasts was positive for both the epithelial sodium channel (ENaC) and the mineralocorticoid receptor (MCR) as 82- to 85-kD and 102-kD bands, respectively, by the Western blot technique. In fluorescent, confocal and electron microscopy, the MCR was revealed as a nucleocytoplasmic protein, whereas the ENaC was almost exclusively membrane bound; both appeared aligned along actin filaments of corneal keratocytes, and both were widely colocalized in various cell types of human cornea in situ. Following reverse transcription and amplification of total RNA isolated from corneal fibroblasts, the ENaC and MCR genes in the PCR product were evident as predicted bands of 520 and 843 bp, respectively, whose sequence exhibited 100% identity with those from known human sources. The multiplication of corneal fibroblasts was influenced by both the MCR-specific antagonist RU 26752 and the natural hormone aldosterone, and these steroids also stimulated protein phosphorylation. In quantitative PCR, both the basal and aldosterone-induced levels of ENaC were diminished by the MCR-specific antagonist ZK 91587. Consequently, the ocular sodium channel appears to be regulated by steroid signalling in cells of diverse embryological origins, contrary to the existing notions where (a) this process would be limited exclusively to the epithelial cells and (b) ocular sodium transport would be regulated via the Na⁺-K⁺-ATPase in the basolateral membrane.

Copyright © 2001 S. Karger AG, Basel

  Author Contacts

M. Mirshahi
Inserm XR-86
15, rue Ecole de Médecine
F–75270 Paris 06 (France)Fax +33 1 40 46 04 39, E-Mail massoud-mirshahi@bhde.jussieu.fr

  Article Information

Received: Received: January 25, 2000
Accepted after revision: May 12, 2000
Number of Print Pages : 13
Number of Figures : 14, Number of Tables : 0, Number of References : 40