Epithelial sodium channel and the mineralocorticoid receptor in cultured rat Müller glial cells.
Müller glial cells are the major non-neuronal cells of the retina. They are involved in retinal function and exert a profound influence on the function of retinal neurons. We present an in vitro study of the localization of the mineralocorticoid receptor (MCR) and of the epithelial sodium channel (ENaC) in rat Müller glial cells isolated from rat retina, using respectively, a polyclonal antiserum raised against the rat purified MCR, and a rabbit polyclonal antibody against the 14-amino acid (aa) peptide QGLGKGDKREEQGL, which corresponds to the N-terminal region (44-58aa) of the alpha-subunit of the ENaC. In an immunocytochemical study using anti-MCR and anti-ENaC antibodies, the MCR was detected as a protein present in the cytoplasm and in the nucleus, whereas ENaC was detected as a membrane-bound protein. Reverse transcription-polymerase chain reaction (RT-PCR) analysis using specific primers, 5'-CTGCCTTTATGGATGATGGT-3' (sense), 5'-GTTCAGCTCGAAGAAGA-3' (antisense) for ENaC and 5'-AGGCTACCACAGTCTCCCTG-3' (sense) and 5'-GCAGTGTAAAATCTCCAGTC-3' (antisense) for MCR, showed expression of the ENaC and MCR genes in Müller cells. The presence of ENaC and MCR was detected as the predicted bands of 520 bp and 843 bp, respectively. In both cases, 100% identity was observed between the sequences of rat Müller cell (RMC) PCR products and rat kidney. Interestingly, the basal levels of ENaC were increased in vitro by the MCR-specific hormone, aldosterone. Thus, our results strongly suggest that the Müller glial cells may play a role in the regulation of extracellular Na+ concentration, which could be regulated by steroid-mediated sodium uptake.
Golestaneh
N
N
INSERM E9912, Faculté de Médecine de Paris, 15 Rue de l'Ecole de Médecine, 75006 Paris, France.
De Kozak
Y
Y
Klein
C
C
Mirshahi
M
M
D000450:Aldosterone / Q000378:metabolism; D000818:Animals; D002451:Cell Compartmentation / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured / Q000737:chemistry / Q000166:cytology; D003599:Cytoskeleton / Q000378:metabolism; D053503:Epithelial Sodium Channels; D005786:Gene Expression Regulation / Q000502:physiology; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009457:Neuroglia / Q000166:cytology* / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011917:Rats, Inbred Lew; D018161:Receptors, Mineralocorticoid / Q000032:analysis* / Q000235:genetics; D012160:Retina / Q000166:cytology* / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid; D015222:Sodium Channels / Q000032:analysis* / Q000235:genetics
D053503:Epithelial Sodium Channels; D012333:RNA, Messenger; D018161:Receptors, Mineralocorticoid; D015222:Sodium Channels; D000450:Aldosterone